On the 21st of August 2020, IEEE Student Branch Chittagong University arranged a webinar on “Thin film solar cell research and manufacturing“ In this webinar, the effect of thin film on the solar panel construction was discussed broadly.

1. Solar power 2020:A
Brief Introduction To My
Experience
Bhuiyan Anwar

2. Distribution of the slides
 Graduate research experience (2017-2018)
 Graduate research experience (2018-2020)
 Internship experience (2020)

3. Graduate Research Experience (2017-
2018)
 Objective was to deposit thin film of a soft magnetic alloy and inspect its
behavior
 Thermal and laser annealing and investigating the crystal structure of the
deposited thin film using XRD.
 The alloy comprised of Fe, Co, Ni, Zr, B, Cu.
 This type of alloys are used to build light weight aircraft and small sized
transformer cores.
 Thin film was deposited by using sputtering
 The thin films were characterized using SEM, EDS,XRD, 4-probe resistivity
measurement system and XRD.

4. Graduate Research
Experience (2017-
2018)
➢ The alloy was different than other soft
magnetic material alloys.
➢ The conventional soft magnetic alloys had
larger grain size.
➢ When the grain size is in nanoscale then
the soft magnetic material behaves
differently.
➢ It is possible to achieve soft magnetic
properties with small sized particles.

5. Graduate Research
Experience (2017-2018)
 The next step of my work was to repair and
reassemble a dysfunctional legacy sputtering
system.
 The films are deposited at different
substrate temperatures and also annealed
after deposition at different temperatures.
 The annealing changed the crystal structures
and that impacts the soft magnetic
properties of the material.
 The next step was to investigate the impact
of laser annealing and compare with furnace
annealing.
Figure. XRD spectra of thin films deposited at
different substrate temperatures
Figure. SEM images of thin films deposited at different
substrate temperatures

6. Graduate Research
Experience (2018-2020)
 I started working at WPVIC.
 In the last decade alone, solar has experienced an average
annual growth rate of 49%.
 There are now more than 81 gigawatts (GW) of solar capacity
installed nationwide, enough to power 15.7 million homes
 In 2019, the solar industry generated $18.7 billion of
investment in the American economy
 The cost to install solar has dropped by more than 70% over the
last decade
 In 2019 one of the world’s top 10 solar cell manufacturing
company was first solar which is situated in Perrysburg, Ohio
(Greater Toledo)
 In the research world NREL just released news of a 50%
efficiency multijunction solar cell
Fig. NREL scientists worked on
the 50% efficiency cell

7. Graduate Research
Experience (2018-
2020)
 This is the time started I
started working with
semiconductor devices.
Namely, CdTe photovoltaic
devices.
Fig. Operation of a photovoltaic cell

8. Graduate Research Experience (2018-
2020)
 I was part of a group working on improving CdTe solar cell
devices.
 CdTe solar cell devices is the one of the most significant
member in the thin film solar cell market.
 Due to the absorption coefficient of CdTe is a good candidate
for thin film solar cells. The current record efficiency 22.1 %
 Cadmium telluride panels can be manufactured at low costs,
as cadmium is abundant and generated as a byproduct of
important industrial materials like zinc.
 On a lifecycle basis, CdTe PV has the smallest carbon
footprint, lowest water use and shortest energy payback
time of any current photo voltaic technology. CdTe's energy
payback time of less than a year allows for faster carbon
reductions without short-term energy deficits.
Fig. Absorption coefficient of CdTe
Fig. CdTe device
structure

9. Graduate Research Experience (2018-
2020)
 Regular day to day work included
fabrication of CdTe solar cell devices
and material characterization using
SEM, EDX, XRD, PL, TRPL, AFM, I-V, QE,
4-probe resistivity measurement.
 First project, Alloying CdTe with ZnTe
and the use ZnCl2 solution instead of
CdCl2 and investigate the structural
changes.
 The CdTe films were deposited by CSS
process. After the deposition of CdS
and CdTe the modules goes through roll
to roll coating belt.
Figure. SEM images of the samples
Figure. CSS deposition of CdTe

10. Graduate Research
Experience (2018-
2020)
 Deep valence band edge of CdTe due to
high electron affinity.
 Makes it harder to form a suitable ohmic
contact
 Band bending is downward toward the
interface
 The heterojunction likely has interface
defects
Fig. Band structure of CdTe

11. Graduate Research Experience (2018-
2020)
 First project, Alloying CdTe with ZnTe
and the use ZnCl2 solution instead of
CdCl2 and investigate the structural
changes.
 The CdTe films were deposited by CSS
process. ZnTe films were sputter
deposited. Then after the activation,
etching , metallization and laser
annealing the devices get ready for
investigation.
 I used SEM, EDS and XRD analysis to aid
the investigation into the structures.
 The grain size, crystal structure and
crystallinity were comparable between
the two different activation solution.
Figure. SEM images of the samples
Figure. XRD spectra of the samples

12. Graduate Research
Experience (2018-
2020)
After that, I moved into other projects that
include
Managing the Band Bending at the Back of
CdTe solar cell devices by implementing
 SWCNTs Films Doped with Tri-ethyl-
oxonium Hexa-chloro-antimonate as a
Transparent Back Contact for CdTe Solar
Cells
 ZnTe and Te Buffer Layers. Te layer
reduces band bending
 CdZnTe thin Film Buffer Layer
Managing Interface defects
 Back Surface Passivation with
Solution‐Processed Oxidized Aluminum
 Co-designed the set experiments to go
through to get the best result and the
information we require. Fig. Experiment Matrix

13. Graduate Research
Experience (2018-
2020)
 I started by doing SEM images on SWCNT
back contact layers.
 Fabricated CdTe devices with solution
processed Al2O3 back buffer layer.
 Al2O3 increases the power conversion
efficiency
 Al2O3 fills up the pinholes of the films
 I also performed SEM, EDS,XRD,PL,TRPL,
AFM, Raman spectroscopy and I-V
measurements of CdTe devices with
Al2O3 back buffer layer.
 Optical characterization of CdTe
devices.
Fig. PL and TRPL for Al2O3 back buffer layer on CdTe
Fig. SEM and AFM of Al2O3 back buffer layer on CdTe

14. Graduate Research
Experience (2018-2020)
 We did MAI treatment and found that it is
also applicable on ZnTe and creates a Te
layer.
 The SWCNTs film can make a low barrier
contact to CdTe
 Band Banding still exists.
 One way to improve the bend bending would
be doped the SWCNTs film but the doped
SWCNT layered devices show a low efficiency
SWCNT
Fig. Raman spectra for different ZnTe
Fig. SWCNT on CdTe

15. Internship Experience
(2020)
 I started my internship as product development engineer in
Toledo Solar.
 The Atlas Venture Group is leading a $30 million initiative to
produce cadmium telluride (Cad-Tel) solar panels operating
as Toledo Solar, Inc. The new company acquired the assets
of Willard & Kelsey Solar Group in May, 2019
 They are also one of the collaborators in my research
 Toledo Solar will begin shipping Tier 1 panels next month
and has already secured $800 million in purchase orders for
solar panels, power converters, and energy storage
systems. The company has 25 employees, but expects that
number to grow to 70 by the end of the year at the
300,000-square-foot facility

16. Internship
Experience (2020)
My internship was done at a up and
coming CdTe solar cell manufacturing
company named Toledo Solar.
I was involved on running the different
processes.
Finishing the devices by soldering and
lamination
Assisting on developing the process of
packaging the devices by making
fixtures.
Fig. CdTe manufacturing process

17. Internship
Experience
(2020)
Failure analysis of CdTe solar
cell devices using image
analysis, EL, Thermography and
IR imaging.
Optimization of manufacturing
processes.
Characterization of devices
using I-V, UV laser based
Ellipsometer, QE.
Stress and tension measurement
of glasses using surface
polarimetry.
Fig. EL images of CdTe solar panels
Fig. Thermography of
CdTe solar panels
Fig. Image processing
through imageJ

18. Questions?