2. Module 1 : Solar
Technology Basics
Module 2:
Solar Photo Voltaic Module Technologies
Module 3: Designing Solar PV
Systems (Rooftops)
Module 4: Designing Solar PV
Systems ( Utility Scale)
Module 5: Financial Analysis
Module 6: DPR (Detailed
Project Report) & EPC
Module 7: The present Solar
industry scenario and the
future
3. Semiconductors used
for solar cells
II III IV V VI
B C (6)
Al Si (14) P S
Zn Ga Ge (32) As Se
Cd In Sb Te
Semiconductors:
Elementary – Si, Ge.
Compound – GaAs, InP, CdTe.
Ternary – AlGaAs, HgCdTe, CIS.
Quaternary – CIGS, InGaAsP, InGaAIP.
5. Technology Differences
Optical Properties
• Band gap (direct, indirect)
• Absorption Coefficient
• Absorption length
Electrical Properties
• Carrier Lifetime
• Mobility
• Diffusion length
Manufacturing
• Absorber material
• Cells
• Modules
Performance
• Efficiency
• Current, Voltage and FF
• Effect of temperature and
radiation
6. Optical Properties:
Band Gaps
Fixed band gap of c-Si material (mono, multi).
Tunable gaps of thin film compound semiconductors.
Once a module is fixed, there can be no modification.
7. Optical Properties:
Direct and Indirect band gap
semiconductor
High absorption probability.
Thinner material only.
Low absorption probability.
Thicker material only.
8. Optical Properties:
Material absorption lengths
Absorption Length in Microns
(for approx. 73% incoming light absorption)
Wavelength (nm) c-Si a-Si CIGS GaAs
400 nm (3.1eV) 0.15 0.05 0.05 0.09
600 nm (2eV) 1.8 0.14 0.06 0.18
800 nm (1.55eV) 9.3 Not absorbed 0.14 1.1
1000nm(1.24eV) 180.9 Not absorbed 0.25 Not absorbed
Absorption length is much higher for Si because of lower absorption
coefficient.
Longer wavelength photons require more materials to get absorbed.
9. Electrical Properties:
Mobility:
Ease with which carriers move in semiconductor.
Lifetime:
Average time carriers spend in excited state.
Diffusion Length:
Average length travelled by carrier before
recombining due to concentration difference.
10. Electrical Properties:
Drift and Diffusion lengths
Diffusion: Carrier movement due to concentration
difference.
Diffusion length: Average length travelled by
carrier before recombination due to concentration
difference.
Drift: Carrier movement due to electric field.
Drift length: Average length travelled by carrier
before recombination under electric field.
11. Electrical Properties:
Drift and Diffusion lengths
High quality material
scenario
Low quality material
scenario
Carrier are transported by diffusion
to the junction.
Large diffusion length.
Junction is very thin.
Diffusion length are small.
Drift length is about 10 times
greater than diffusion length.
Intrinsic layer is thicker.
12. Manufacturing:
The difference
Crystalline
Technology
Thin Film
Mono-crystalline and Poly-
crystalline Si substrates are grown.
The substrate act as a light
absorber material.
The absorber layer is deposited in
the thin film cells.
A supporting substrate is required
since the films are thin.
13. Performances
Average module efficiencies are increasing for all technologies.
PV module efficiencies lag behind as compared to laboratory
cell efficiencies.
14. Temperature Coefficient
Thin Film modules perform better due to smaller temperature
coefficient.
Temperature Coefficient could result in higher electricity
generation.