Adding quantum wells to the intrinsic region of a p-i-n solar cell improves its conversion efficiency in the following ways:
1. Quantum wells allow a wider range of photon energies to be absorbed by shifting electrons to higher energy levels. This improves the solar spectrum absorption.
2. Electron-hole pairs generated in the quantum wells have a longer lifetime, increasing the probability that they will separate and be collected before recombining.
3. The quantum wells act as intermediate energy levels, allowing photons of lower energy to still promote electrons provided the energy difference is matched by the quantum well transition.
However, limitations include the solar spectrum not being truly monochromatic, so not all energies can be utilized.
This document provides an introduction to semiconductor devices. It discusses band theory and defines key concepts like the valence band, conduction band, and forbidden gap. It explains that semiconductors have a small forbidden gap that electrons can cross with a small amount of energy. Intrinsic and extrinsic semiconductors are introduced, along with p-type and n-type materials which are formed by doping. The document describes how a p-n junction forms a depletion zone and allows current to flow in one direction but not the other. Applications like solar cells, LEDs, and lasers are briefly outlined.
This chapter discusses electrical conduction processes in materials and semiconductor devices. It begins by describing conduction in metals, semiconductors, and doped semiconductors. Next, it covers the p-n junction, including the formation of a space-charge layer and drift and diffusion currents. The characteristics of the p-n junction and diode are then explained. The chapter concludes by discussing maximum power dissipation and voltage limitations in diodes due to avalanche and Zener breakdown.
This article gives a vivid description of the principle and working procedure of a Light Emitting Diode. It provides a comprehensive understanding of how this very important optical device is useful in our daily applications, its types, structure and other related information.
Optoelectronics is a branch of physics and technologyakhilsaviour1
Optoelectronics is a branch of physics and technology focused on the interaction between light and electronic devices. It encompasses devices like LEDs, photodiodes, and optical fibers, playing crucial roles in telecommunications, medical imaging, and many other applications.
Principle And Working of A Semiconductor Laser.pptxRehmanRasheed3
The document summarizes the principles and working of a semiconductor laser, explaining that it uses stimulated emission from a p-n junction diode made of gallium arsenide to produce coherent infrared laser light, and that applying a forward voltage bias injects electrons and holes to achieve population inversion and trigger stimulated recombination of photons within the diode's optical resonator structure. Semiconductor lasers have applications in fiber optic communication, wound healing, laser printing, and CD/DVD reading/writing due to their compact size, high efficiency, and ability to produce continuous or pulsed laser output.
The document summarizes the principles and working of a semiconductor laser, explaining that it uses stimulated emission from a p-n junction diode made of gallium arsenide to produce coherent infrared laser light, and that applying a forward voltage bias injects electrons and holes to achieve population inversion and trigger stimulated recombination of photons within the diode's optical resonator structure. Semiconductor lasers have applications in fiber optic communication, wound healing, laser printing, and CD/DVD reading/writing due to their compact size, high efficiency, and ability to produce continuous or pulsed laser output.
Lasers & semiconductors 2008 prelim solutionsJohn Jon
Electrons and holes are urged towards the junction region when the diode is in forward bias. This results in the reduction of the depletion region, thus allowing a current to flow. When a p-d is applied across a p-n junction diode in the forward bias mode, the width of the depletion layer decreases, allowing charge carriers to flow more easily across the junction. In reverse bias mode, the depletion layer width increases, preventing charge flow and making the diode act as an open switch.
Adding quantum wells to the intrinsic region of a p-i-n solar cell improves its conversion efficiency in the following ways:
1. Quantum wells allow a wider range of photon energies to be absorbed by shifting electrons to higher energy levels. This improves the solar spectrum absorption.
2. Electron-hole pairs generated in the quantum wells have a longer lifetime, increasing the probability that they will separate and be collected before recombining.
3. The quantum wells act as intermediate energy levels, allowing photons of lower energy to still promote electrons provided the energy difference is matched by the quantum well transition.
However, limitations include the solar spectrum not being truly monochromatic, so not all energies can be utilized.
This document provides an introduction to semiconductor devices. It discusses band theory and defines key concepts like the valence band, conduction band, and forbidden gap. It explains that semiconductors have a small forbidden gap that electrons can cross with a small amount of energy. Intrinsic and extrinsic semiconductors are introduced, along with p-type and n-type materials which are formed by doping. The document describes how a p-n junction forms a depletion zone and allows current to flow in one direction but not the other. Applications like solar cells, LEDs, and lasers are briefly outlined.
This chapter discusses electrical conduction processes in materials and semiconductor devices. It begins by describing conduction in metals, semiconductors, and doped semiconductors. Next, it covers the p-n junction, including the formation of a space-charge layer and drift and diffusion currents. The characteristics of the p-n junction and diode are then explained. The chapter concludes by discussing maximum power dissipation and voltage limitations in diodes due to avalanche and Zener breakdown.
This article gives a vivid description of the principle and working procedure of a Light Emitting Diode. It provides a comprehensive understanding of how this very important optical device is useful in our daily applications, its types, structure and other related information.
Optoelectronics is a branch of physics and technologyakhilsaviour1
Optoelectronics is a branch of physics and technology focused on the interaction between light and electronic devices. It encompasses devices like LEDs, photodiodes, and optical fibers, playing crucial roles in telecommunications, medical imaging, and many other applications.
Principle And Working of A Semiconductor Laser.pptxRehmanRasheed3
The document summarizes the principles and working of a semiconductor laser, explaining that it uses stimulated emission from a p-n junction diode made of gallium arsenide to produce coherent infrared laser light, and that applying a forward voltage bias injects electrons and holes to achieve population inversion and trigger stimulated recombination of photons within the diode's optical resonator structure. Semiconductor lasers have applications in fiber optic communication, wound healing, laser printing, and CD/DVD reading/writing due to their compact size, high efficiency, and ability to produce continuous or pulsed laser output.
The document summarizes the principles and working of a semiconductor laser, explaining that it uses stimulated emission from a p-n junction diode made of gallium arsenide to produce coherent infrared laser light, and that applying a forward voltage bias injects electrons and holes to achieve population inversion and trigger stimulated recombination of photons within the diode's optical resonator structure. Semiconductor lasers have applications in fiber optic communication, wound healing, laser printing, and CD/DVD reading/writing due to their compact size, high efficiency, and ability to produce continuous or pulsed laser output.
Lasers & semiconductors 2008 prelim solutionsJohn Jon
Electrons and holes are urged towards the junction region when the diode is in forward bias. This results in the reduction of the depletion region, thus allowing a current to flow. When a p-d is applied across a p-n junction diode in the forward bias mode, the width of the depletion layer decreases, allowing charge carriers to flow more easily across the junction. In reverse bias mode, the depletion layer width increases, preventing charge flow and making the diode act as an open switch.
The document summarizes optical properties of nanomaterials. It discusses topics like optics, optical properties of materials, thin film interference, luminescence, photonic crystals, photoconductivity, solar cells, and optical properties of quantum wells and quantum dots. In particular, it explains how the size-dependent band gap of quantum dots leads to size-tunable fluorescence colors, making quantum dots useful for applications like biological imaging and white LEDs.
This document provides an overview of a presentation on solar cells given at Kwame Nkrumah University of Science & Technology in Ghana. The presentation covers the structure and operation of solar cells, materials used in solar panels, solar panel design, applications of solar cells, and concludes with references. Solar cells convert sunlight directly into electricity via the photovoltaic effect and do not require chemical reactions or moving parts like other energy sources. They are made of semiconducting materials arranged in a structure that separates light-generated electron-hole pairs to produce a voltage and current.
1. The document discusses various topics related to antenna parameters and radiation patterns. It describes the radiation mechanism of single wire, two wire, and dipole antennas.
2. Current distribution on thin wire antennas is explained. Parameters like radiation patterns, patterns in principal planes, main lobe and side lobes, beam widths, and polarization are discussed.
3. Key points about radiation patterns, coordinate systems, principal plane patterns, and definitions of main lobe, side lobes, half power beamwidth and first null beamwidth are provided.
By growing a superlattice of alternating Indium Aluminum Nitride (InAlN) and Gallium Nitride (GaN) layers, a conduction band offset is formed which allows for intersubband transitions in the quantized energy levels. These intersubband transitions provide access to previously inaccessible mid-infrared energy ranges from 1.5-3.0 μm. Fourier Transform Infrared Spectroscopy is used to measure absorption spectra from the superlattice and analyze the intersubband transitions under direct and photoinduced absorption methods.
A solar cell converts light into electricity via the photovoltaic effect. When light reaches the p-n junction of a semiconductor, electron-hole pairs are created which generate a voltage across the junction. The newly created electrons and holes are separated to the n-type and p-type sides respectively due to the junction's barrier potential, creating a small current flow if a load is connected. Common semiconductor materials used in solar cells include silicon, gallium arsenide, cadmium telluride, and copper indium selenide due to their band gaps close to 1.5 electronvolts.
1. The document discusses various semiconductor devices including diodes, transistors, and integrated circuits. It describes how pn junctions allow current to flow easily in one direction.
2. Key devices are discussed like Zener diodes, light-emitting diodes, solar cells, bipolar junction transistors, field effect transistors, and integrated circuits.
3. The document also covers nanotechnology, describing carbon nanotubes and their applications as well as potential for nanoscale electronics and use in life sciences.
This document discusses solar cells and photovoltaic technology. It begins by defining a solar cell as a device that converts light energy into electrical energy through the photovoltaic effect. It then discusses the materials used in solar cells, such as semiconductors like silicon, and the p-n junction structure that is the building block of solar cells. Finally, it covers losses in solar cells and ways to minimize them, as well as different types of solar cells including commercial silicon cells.
1. The document discusses the principles and working of solar cells. It describes how solar cells convert sunlight into electrical energy through the photovoltaic effect.
2. Solar cells are made from semiconducting materials like silicon that produce electron-hole pairs when exposed to light. At the junction between the n-type and p-type semiconductors, electrons flow, generating an electric current.
3. Single solar cells produce small amounts of power. Solar panels connect multiple cells together to increase electricity production and provide usable amounts of power for applications like water pumping and powering homes.
The document provides an introduction to optoelectronic devices, including their operation and key properties. It discusses:
1) The wave nature of light and how it is described by Maxwell's equations.
2) Polarization and the electromagnetic spectrum, including visible, infrared, and ultraviolet light ranges.
3) Types of optoelectronic devices like p-n junction diodes, heterojunction diodes, laser diodes, photoconductive cells, pin photodiodes, avalanche photodiodes, and photovoltaic cells. It provides details on their principles, structures, and applications.
Diploma sem 2 applied science physics-unit 3-chap-1 band theory of solidRai University
This document provides an overview of band theory of solids. It discusses key concepts such as effective mass of electrons, the concept of holes, and the energy band structure of conductors, semiconductors and insulators. It explains that conductors have overlapping valence and conduction bands, semiconductors have a small bandgap, and insulators have a large bandgap. The document also covers intrinsic and extrinsic semiconductors, the operation of p-n junction diodes under reverse and forward bias, and types of diodes such as simple diodes and Zener diodes.
This document provides an overview of photodiode detectors. It discusses the background concepts of p-n photodiodes and their photoconductive and photovoltaic modes of operation. It also covers p-i-n photodiode structures, responsivity and bandwidth characteristics, and noise in photodetectors. Key points include the generation of electron-hole pairs through absorption of photons, drift and diffusion currents, dependence of short-circuit current and open-circuit voltage on light intensity, and the basic circuitry and load lines for photoconductive and photovoltaic modes of a photodiode.
Unit 3- OPTICAL SOURCES AND DETECTORS tamil arasan
This document discusses optical sources and detectors used in fiber optic communications. It describes light emitting diodes (LEDs) and laser diodes as the main optical sources. LEDs use a double heterostructure to provide carrier and optical confinement for high efficiency. They emit incoherent light without an optical cavity. Laser diodes function as coherent sources using a Fabry-Perot cavity formed by cleaved facets to provide optical feedback, producing highly directional and monochromatic output. Factors such as modulation capability and fiber characteristics must be considered when choosing an optical source.
- When p-type and n-type semiconductors are placed in contact, a p-n junction is formed that allows current to flow easily in one direction but not the other, creating a basic diode.
- At the junction, electrons from the n-type region diffuse into the p-type region, leaving positive ions. This creates an electric field that opposes further diffusion, known as the depletion zone.
- Solar cells use wafer thin p-n junction diodes to convert solar energy into electrical energy. When light enters the junction, it creates electron-hole pairs, generating a photovoltage if the pairs separate across the junction.
A Hybrid Model to Predict Electron and Ion Distributions in Entire Interelect...Fa-Gung Fan
Atmospheric direct current (dc) corona discharge
from thin wires or sharp needles has been widely used as an ion
source in many devices such as photocopiers, laser printers, and
electronic air cleaners. Existing numerical models to predict the
electron distribution in the corona plasma are based on charge
continuity equations and the simplified Boltzmann equation. In
this paper, negative dc corona discharges produced from a thin
wire in dry air are modeled using a hybrid model of modified
particle-in-cell plus Monte Carlo collision (PIC-MCC) and a
continuum approach. The PIC-MCC model predicts densities of
charge carriers and electron kinetic energy distributions in the
plasma region, while the continuum model predicts the densities of
charge carriers in the unipolar ion region. Results from the hybrid
model are compared with those from prior continuum models.
Superior to the prior continuum model, the hybrid model is able
to predict the voltage–current curve of corona discharges. The
PIC-MCC simulation results also suggest the validity of the local
approximation used to solve the Boltzmann equation in the prior
continuum model.
Pv fundamentals by Ecoepicsolar training divisionecoepicsolar
1. Solar cells convert light energy from the sun into electrical energy through the photovoltaic effect. When light is absorbed by semiconductor materials, electrons are released and leave behind holes, creating an electric current.
2. A solar cell is made of doped semiconductor materials arranged to form a p-n junction, typically using silicon. Absorbed photons create electron-hole pairs that are separated at the junction to generate voltage.
3. Multiple solar cells are connected and encapsulated between glass or plastic to form a solar panel or module. Panels can be interconnected in an array to increase voltage and power output for applications such as water pumping, household electricity supply, and large-scale solar power plants.
This document describes the operation of a Tesla transformer, which uses primary and secondary coils to generate high voltage pulses. It explains that the primary coil discharges energy into the secondary coil, which transforms the magnetic pulse into an electric wave. This wave is then further magnified as it travels along the Tesla coil due to its high impedance and low capacitance. The electric field gradient sharply increases near the end of the Tesla coil and the terminal sphere, where a high voltage potential is produced for wireless energy transmission or other experiments.
Solar Cells Technology: An Engine for National DevelopmentIOSR Journals
This document provides an overview of solar cell technology. It discusses how solar cells work based on the electronic properties of semiconductors. Solar cells use n-type and p-type semiconductors to generate an electric field that separates electrons and holes when exposed to light, producing electricity. The document also examines the structures of different solar cell materials like crystalline silicon, amorphous silicon, cadmium telluride, and gallium arsenide. It reviews trends showing decreasing costs over time for the silicon material, the solar cells, and solar modules.
This document summarizes a seminar on energy bands and gaps in semiconductors. It discusses the introduction of energy bands, including valence bands, conduction bands, and forbidden gaps. It describes how materials are classified as insulators, conductors, or semiconductors based on their band gap energies. Direct and indirect band gap semiconductors are also defined. Intrinsic, n-type, and p-type semiconductors are classified based on their majority charge carriers.
B.tech sem i engineering physics u ii chapter 1-band theory of solidRai University
This document provides an overview of band theory of solids. It discusses effective mass of electrons in solids, the concept of holes, and the energy band structure of conductors, semiconductors, and insulators. Intrinsic and extrinsic semiconductors are described, along with p-type and n-type materials. Simple diode and Zener diode operation is summarized, including forward and reverse bias conditions.
The document discusses different types of special-purpose diodes used in electronics. It explains the construction and working of n-type and p-type semiconductors by doping silicon with different impurity atoms. The depletion region that forms when an n-type and p-type material are joined is also described. Different diodes are then explained, including light-emitting diodes, varactor diodes, tunnel diodes, Schottky barrier diodes, and photodiodes. Their key characteristics and applications are provided in brief. Circuit diagrams demonstrate how diodes can be used as switches and in tuning networks.
You are the information technology manager of an.docx4934bk
The IT manager of an 80-bed long-term care facility was tasked by the Board of Directors and CIO to create a 1-2 page report on private databases and doctor-patient privilege. The report aims to summarize the types of data stored in private health databases and whether it is protected by specific regulations or doctor-patient privilege. Private databases store confidential patient information like medical history and treatment plans. This data is regulated under laws like HIPAA which require security and privacy of sensitive medical information. Doctor-patient privilege legally protects confidential patient information and communications, though it has limits such as in response to court orders.
Your parents gave you up for adoption at a.docx4934bk
Your biological parents gave you up for adoption as a young child because they could not financially support you at the time. Thirty years later, they found you and one of your biological parents needs a kidney transplant. You are the best match to donate a kidney. You must determine whether you have a moral obligation to donate your kidney to your biological parent based on philosophical perspectives of ethics and your own cultural worldview.
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The document summarizes optical properties of nanomaterials. It discusses topics like optics, optical properties of materials, thin film interference, luminescence, photonic crystals, photoconductivity, solar cells, and optical properties of quantum wells and quantum dots. In particular, it explains how the size-dependent band gap of quantum dots leads to size-tunable fluorescence colors, making quantum dots useful for applications like biological imaging and white LEDs.
This document provides an overview of a presentation on solar cells given at Kwame Nkrumah University of Science & Technology in Ghana. The presentation covers the structure and operation of solar cells, materials used in solar panels, solar panel design, applications of solar cells, and concludes with references. Solar cells convert sunlight directly into electricity via the photovoltaic effect and do not require chemical reactions or moving parts like other energy sources. They are made of semiconducting materials arranged in a structure that separates light-generated electron-hole pairs to produce a voltage and current.
1. The document discusses various topics related to antenna parameters and radiation patterns. It describes the radiation mechanism of single wire, two wire, and dipole antennas.
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A solar cell converts light into electricity via the photovoltaic effect. When light reaches the p-n junction of a semiconductor, electron-hole pairs are created which generate a voltage across the junction. The newly created electrons and holes are separated to the n-type and p-type sides respectively due to the junction's barrier potential, creating a small current flow if a load is connected. Common semiconductor materials used in solar cells include silicon, gallium arsenide, cadmium telluride, and copper indium selenide due to their band gaps close to 1.5 electronvolts.
1. The document discusses various semiconductor devices including diodes, transistors, and integrated circuits. It describes how pn junctions allow current to flow easily in one direction.
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This document discusses solar cells and photovoltaic technology. It begins by defining a solar cell as a device that converts light energy into electrical energy through the photovoltaic effect. It then discusses the materials used in solar cells, such as semiconductors like silicon, and the p-n junction structure that is the building block of solar cells. Finally, it covers losses in solar cells and ways to minimize them, as well as different types of solar cells including commercial silicon cells.
1. The document discusses the principles and working of solar cells. It describes how solar cells convert sunlight into electrical energy through the photovoltaic effect.
2. Solar cells are made from semiconducting materials like silicon that produce electron-hole pairs when exposed to light. At the junction between the n-type and p-type semiconductors, electrons flow, generating an electric current.
3. Single solar cells produce small amounts of power. Solar panels connect multiple cells together to increase electricity production and provide usable amounts of power for applications like water pumping and powering homes.
The document provides an introduction to optoelectronic devices, including their operation and key properties. It discusses:
1) The wave nature of light and how it is described by Maxwell's equations.
2) Polarization and the electromagnetic spectrum, including visible, infrared, and ultraviolet light ranges.
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This document provides an overview of photodiode detectors. It discusses the background concepts of p-n photodiodes and their photoconductive and photovoltaic modes of operation. It also covers p-i-n photodiode structures, responsivity and bandwidth characteristics, and noise in photodetectors. Key points include the generation of electron-hole pairs through absorption of photons, drift and diffusion currents, dependence of short-circuit current and open-circuit voltage on light intensity, and the basic circuitry and load lines for photoconductive and photovoltaic modes of a photodiode.
Unit 3- OPTICAL SOURCES AND DETECTORS tamil arasan
This document discusses optical sources and detectors used in fiber optic communications. It describes light emitting diodes (LEDs) and laser diodes as the main optical sources. LEDs use a double heterostructure to provide carrier and optical confinement for high efficiency. They emit incoherent light without an optical cavity. Laser diodes function as coherent sources using a Fabry-Perot cavity formed by cleaved facets to provide optical feedback, producing highly directional and monochromatic output. Factors such as modulation capability and fiber characteristics must be considered when choosing an optical source.
- When p-type and n-type semiconductors are placed in contact, a p-n junction is formed that allows current to flow easily in one direction but not the other, creating a basic diode.
- At the junction, electrons from the n-type region diffuse into the p-type region, leaving positive ions. This creates an electric field that opposes further diffusion, known as the depletion zone.
- Solar cells use wafer thin p-n junction diodes to convert solar energy into electrical energy. When light enters the junction, it creates electron-hole pairs, generating a photovoltage if the pairs separate across the junction.
A Hybrid Model to Predict Electron and Ion Distributions in Entire Interelect...Fa-Gung Fan
Atmospheric direct current (dc) corona discharge
from thin wires or sharp needles has been widely used as an ion
source in many devices such as photocopiers, laser printers, and
electronic air cleaners. Existing numerical models to predict the
electron distribution in the corona plasma are based on charge
continuity equations and the simplified Boltzmann equation. In
this paper, negative dc corona discharges produced from a thin
wire in dry air are modeled using a hybrid model of modified
particle-in-cell plus Monte Carlo collision (PIC-MCC) and a
continuum approach. The PIC-MCC model predicts densities of
charge carriers and electron kinetic energy distributions in the
plasma region, while the continuum model predicts the densities of
charge carriers in the unipolar ion region. Results from the hybrid
model are compared with those from prior continuum models.
Superior to the prior continuum model, the hybrid model is able
to predict the voltage–current curve of corona discharges. The
PIC-MCC simulation results also suggest the validity of the local
approximation used to solve the Boltzmann equation in the prior
continuum model.
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1. Solar cells convert light energy from the sun into electrical energy through the photovoltaic effect. When light is absorbed by semiconductor materials, electrons are released and leave behind holes, creating an electric current.
2. A solar cell is made of doped semiconductor materials arranged to form a p-n junction, typically using silicon. Absorbed photons create electron-hole pairs that are separated at the junction to generate voltage.
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This document summarizes a seminar on energy bands and gaps in semiconductors. It discusses the introduction of energy bands, including valence bands, conduction bands, and forbidden gaps. It describes how materials are classified as insulators, conductors, or semiconductors based on their band gap energies. Direct and indirect band gap semiconductors are also defined. Intrinsic, n-type, and p-type semiconductors are classified based on their majority charge carriers.
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This document provides an overview of band theory of solids. It discusses effective mass of electrons in solids, the concept of holes, and the energy band structure of conductors, semiconductors, and insulators. Intrinsic and extrinsic semiconductors are described, along with p-type and n-type materials. Simple diode and Zener diode operation is summarized, including forward and reverse bias conditions.
The document discusses different types of special-purpose diodes used in electronics. It explains the construction and working of n-type and p-type semiconductors by doping silicon with different impurity atoms. The depletion region that forms when an n-type and p-type material are joined is also described. Different diodes are then explained, including light-emitting diodes, varactor diodes, tunnel diodes, Schottky barrier diodes, and photodiodes. Their key characteristics and applications are provided in brief. Circuit diagrams demonstrate how diodes can be used as switches and in tuning networks.
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ENSC3014 Electronic Materials And Devices.docx
1. ENSC3014 Electronic Materials And Devices
Answers:
1. A pn junction can be used as a solar cell. Describe how this is possible. Describe the
limitations to the conversion efficiency of solar radiation to electric power in a silicon pn
junction solar cell. Explain how you would improve the pn-junction conversion efficiency
A p-n junction can be used as a solar cell. Describe how this is possible
P–N junctions are the boundary or interface between the several forms of semiconductor
that make up a single crystal of semiconductor. There are several ways to achieve this, such
as ion implantation or diffusion of dopants or epitaxy. There will be a grain boundary
between the semiconductors if they are made of two distinct materials, which will
drastically reduce their value by spreading electrons and holes over the material's surface.
Electrical energy can only be created when light-generated carriers are accumulated.
Electricity can only be generated when there is a voltage and current present. Photovoltaic
effect" creates the voltage in a solar cell. Carriers created by light enter the junction and
move to the other side of the p-n junction, where electrons are collected and holes are
dispersed. As light-generated energy takes over when a circuit is shorted, no charge is left in
the gadget. (Gharghi et al., 2006).
Describe the limitations to the conversion efficiency of solar radiation to electric power in a
silicon p-n junction solar cell
There is an increase in electrons and holes on the n-type side of the p-n junction as a result
of the accumulation of light-generated carriers. An opposing electric field is created at the
connection as a result of this charge separation. As the electric field functions as a barrier, it
is important to reduce the electric field in order to enhance the forward’s bias diffusion
current (Shockley et al., 1961). A new equilibrium is established when a voltage from across
p-n junction is applied. The voltage output of the solar cell is the difference between the
forward current and the IL current. Forward bias grows under open-circuit circumstances
until the light-generated current is entirely matched by the junction's forward bias diffusion
current, at which time the net flow is zero. To equalize these two currents, "open-circuit
voltage" is the phrase used. (Gharghi et al., 2006).
2. Explain how you would improve the pn-junction conversion efficiency.
Minimizing the amount of light being reflected away from the cell surface
Using anti-reflective coatings
Using and promoting light scattering visible spectrum
Using light trapping photonic structures to increase the cell’s conversion efficiencies.
Use of optimum transparent conductors
Improving charge carrier collection
2.One way to improve power conversion efficiency is to design a p-i-n device. Explain how
this improves the efficiency and what are the limitations of this method
To activate the PIN photodiode when the reverse bias voltage is applied, the space charge
area must entirely cover the intrinsic region. In the space charge area, photon absorption
forms electron-hole pairs. Due to its limited lifespan, its switching speed is inversely
proportional to it.
A short minority carrier lifespan contributes to the acceleration of the switching process. To
maximize switch speed in light detector applications where response time is crucial, the
depletion area width should be as large as possible with a very short minority carrier
lifetime (William et al., 1999). PIN photodiodes may do this by introducing an intrinsic
region that increases the breadth of the space charge. The image below shows a standard
PIN photodiode:
How this improves the efficiency:
Has a low bias current
Has low dark current
Has the high-speed response
Has a low junction capacitance
Has a large depletion region
Can tolerate high reverse bias voltages. (William et al., 1999).
What are the limitations of this method?
It is less sensitive
Has a high reverse recovery time that makes it lose a lot of power
Does not have an internal gain
Has a smaller area. (William et al., 1999).
3. 3. Another way to improve efficiency is to add quantum wells to the i-region of the p-i-n
device. Explain how this improves the efficiency of conversion and what are the limitations
of this method. (30 marks)
A solar cell
When photons strike the p-n junction in the presence of light, electrons form pairs and an
electric current flows through the depletion zone, where electrons from n-type Silicone
have spread into holes in the p-type Silicone. When photons are absorbed by atoms, the free
one electron from the atom and cause a hole to form in the atom's structure. Those that
have enough energy to make it out of the depletion zone without depleting all of their
resources are considered to be survivors (Barnham et al., 1993).
When a wire is connected from the cathode (N) to the anode (O), it is feasible for electrons
to flow through it (p). The introduction of an external load causes electrons to be pulled to P
and holes to be drawn to N, resulting in the passage of current across the circuit (Barnham
et al., 1993).
Limitations of this method.
It has a high maintenance cost
Bandgap selects only at a few frequencies to shift electrons
As sunlight is not monochromatic and energy is spread over a spectrum
References
Barnham, K., Barnes, J., Haarpaintner, G., Nelson, J., Paxman, M., Foxon, T., & Roberts, J.
(1993). Quantum-well solar cells. MRS Bulletin, 18(10), 51-55. Retrieved from:
https://www.cambridge.org/core/journals/mrs-bulletin/article/quantumwell-solar-
cells/79E0B02E8AA2E2231E90775F0E420F07
Gharghi, M., Bai, H., Stevens, G., & Sivoththaman, S. (2006). Three-dimensional modeling and
simulation of pn junction spherical silicon solar cells. IEEE transactions on electron devices,
53(6), 1355-1363. References: https://ieeexplore.ieee.org/abstract/document/1637631/
Shockley, W., & Queisser, H. J. (1961). Detailed balance limit of efficiency of p?n junction
solar cells. Journal of applied physics, 32(3), 510-519. Retrieved from:
https://aip.scitation.org/doi/abs/10.1063/1.1736034
Williams, K. J., & Esman, R. D. (1999). Design considerations for high-current
