module 2/7: solar pv module technologies. module 1 : solar technology basics module 2: solar photo...
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Module 2/7: Solar PV Module
Technologies
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
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.
Cell TechnologiesCrystalline silicon
Mono-crystalline
Pure and efficient
15-19% efficiency
Multi-crystalline
12-15% efficiency
Thin film
Non Silicon based
CdTe
8.5% efficiency
CIGS
9-11% efficiency
Silicon based
Amorphous
5-7% efficiency
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
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.
Optical Properties: Direct and Indirect band gap
semiconductor
High absorption probability. Thinner material only.
Low absorption probability. Thicker material only.
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.
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.
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.
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.
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.
Performances
Average module efficiencies are increasing for all technologies. PV module efficiencies lag behind as compared to
laboratory cell efficiencies.
Temperature Coefficient
Thin Film modules perform better due to smaller temperature coefficient.
Temperature Coefficient could result in higher electricity generation.
Shading Effects