1. Photoconductivity in nanocomposite films of
PbS nanocrystals and insulating polymers
Principal Investigator (PI)
Prof. Tapas Kumar Chaudhuri
Dr. K. C. Patel Research and Development Centre
Co-PI
Prof. Arabinda Ray
P. D. Patel Institute of Applied Sciences
Changa, Anand District, Gujarat

2. Background [Chaudhuri et al., Phys. Status Solidi A 210 (2013) 356-360]
We have observed photoconductivity in nanocomposite films of polystyrene
(insulator, non-photoactive) and PbS nanocrystals (semiconductor, photoactive).
Electrical conductivity (S/cm):
Polystyrene: ~ 10-16
PbS film (without PSt): ~ 10-2
PbS/polystyrene (dark, σL): 5 x 10-6
Thermoelectric power: positive
Steady light (80 mW/cm2 halogen lamp)
PbS/polystyrene (light, σD): 2.5 x 10-4 S/cm
Photoconductivity (ΔσPH = σL – σD): 2.45 x 10-4
Photosensitivity (ΔσPH / σD): 49
Transient photoconductivity: 2 lifetimes: 18 ms (fast) & 25 s (Slow)
FTIR and TGA: Strong interaction between PbS and polystyrene
Properties due
to overlap of
HOMOs of PSt
and PbS
PbS/PSt
behaves like an
Ohmic
semiconductor
Band gap of PbS (Tauc plot): ~ 1 eV
PbS : 24 % v/v
(< percolation)

3. Major objective
To study and elucidate the phenomenon of photoconductivity in
nanocomposite films of PbS nanoparticles and an insulating polymer
Specific Objectives
1.To deposit photoconducting thin films of PbS/polymer nanocomposites of
different compositions
2.To study the electronic transport properties of these nanocomposites as a
function of composition
3.To study steady and transient photoconductivity in nanocomposites as a
function of composition
• Duration: 36 months

4. Precursor solution:
Polymer, Pb salt,
thiourea, solvents,
Dip or Spin
coating of
precursor film
PbS/polymer nanocomposite films
Different proportions of PbS
Different types of polymer
Characterization
XRD, AFM, SEM, EDAX, roughness, thickness,
transmittance and reflectance spectra, band gap
Annealing:
in situ thermolysis
Drying
Electrical Transport Properties (in dark)
Conductivity, Thermoelectric power, Hall
coefficient, carrier concentration, mobility
Temperature variation: 77 to 373 K
Electrical Transport Properties (under light)
Photoconductivity, Photo-thermoelectric
power, carrier concentration, mobility,
minority carrier lifetime, decay,
photoconductivity spectra, IPCE/QE, etc.
Temperature variation: 77 to 373 K
PbS-polymer interaction
FTIR, TGA, DSC, XPS
Precursor solution:
Polymer, Pb salt,
thiourea, solvents,
Dip or Spin
coating of
precursor film
PbS/polymer nanocomposite films
Different proportions of PbS
Different types of polymer
Characterization
XRD, AFM, SEM, EDAX, roughness, thickness,
transmittance and reflectance spectra, band gap
Annealing:
in situ thermolysis
Drying
Electrical Transport Properties (in dark)
Conductivity, Thermoelectric power, Hall
coefficient, carrier concentration, mobility
Temperature variation: 77 to 373 K
Electrical Transport Properties (under light)
Photoconductivity, Photo-thermoelectric
power, carrier concentration, mobility,
minority carrier lifetime, decay,
photoconductivity spectra, IPCE/QE, etc.
Temperature variation: 77 to 373 K
PbS-polymer interaction
FTIR, TGA, DSC, XPS
Methodology

5. ACTIVITY
MONTHS
First Year Second Year Third Year
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
1.Recruitment
of staff
2. Purchases
3. Synthesis of
nanocomposite
films
4. Composition,
structural, etc.
characterization
5. Interaction
studies
6. Transport
properties in
dark
7. Transport
properties in
light
8. Analysis and
Report
Time Schedule

6. Items Year 1
(Rs in Lakh)
Year 2
(Rs in Lakh)
Year 3
(Rs in Lakh)
Total
Manpower* 1.92 1.92 2.16 6
Consumables 0.75 0.25 0.25 1.25
Travel 0.50 0.50 0.50 1.50
Contingency 0.30 0.30 0.30 0.90
Institute Overhead
(@15%)
6.6 0.48 0.52 7.6
Other Cost 0.25 0.25 0.25 0.75
Equipment 40 Nil Nil 40
Total 50.32 3.7 3.98 58
Budget
*JRF (1) : Rs 16000 p.m. for 1st & 2nd Years; Rs. 18000 p.m. for 3rd Year

7. Generic name of Equipment Imported /
Indigenous
Cost in
Rs.
(Lakhs)
Cost in
US $
Year of
Procurement
1. Cryostat for measurement of
conductivity, photoconductivity
and Thermoelectric Power
measurements (77 to 373 K)
Imported 12 20,000 1
2. Set-up for Spectral response
of photoconductivity and
photoconductivity decay (PCD):
Monochromator (300 to 1400
nm), Optical Chopper, Light and
IR source, Lock-in-amplifier,
detectors, quartz lenses,
preamplifier, optical bench.
Imported 20 36,000 1
3. Digital Storage Oscilloscope Indigenous 4 1
4. Vacuum system Indigenous 5 1
Total 40 56,000
Budget for equipment