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National Center for Photovoltaic Research and Education (NCPRE)

Indian Institute of Technology Bombay

CMIA Energy Conclave, 2013

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II III IV V VI

B C(6)

Al Si(14) P S

Zn Ga Ge(32) As Se

Cd In Sb Te

Elemental semiconductors: Si, Ge Compound semiconductors: GaAs, InP, CdTe Ternary semiconductors: AlGaAs, HgCdTe, CIS Quaternary semiconductors: CIGS, InGaAsP,

InGaAlP04/10/23National Center for Photovoltaic Research and Education (NCPRE)

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A solar cell should convert light into electricity with high efficiency

It requires

- Absorption of a photon

- Separation of a electron-hole pair

- Collection of the charges at electrodes

Different solar cell technologies strives to maximize the efficiency of the above three operations in different way

P-N Jn –separation force

Metal contact

Metal contact

c-Si Solar Cells

Mono-crystalline

Multi Crystalline

Companies

Material Type

Sanyo, SunPower, SunTech, Trina, Sharp, Kyocera

EverGreen

Csun, Qcells, Trina, Canadian Solar, Sharp, Kyocera

Ribbon Si

All these technologies are commercially available04/10/23 © IIT Bombay, C.S. Solanki 4National Center for Photovoltaic Research and Education (NCPRE)

Thin film Solar Cells

Silicon Based

Non Silicon Based

Amorphous Silicon

Other thin film

CdTe

CIGS

Organic/DSC

Flexible

Rigid

Flexible

Rigid

Rigid

Flexible

Rigid

Flexible

Companies

SubstrateAbsorber Layer

Material Type

Unisolar, Flexcell

Kaneka, Sharp, EPV

Innovalight

CSG Solar, Nanogram

First Solar, AVA Tech

Nanosolar, Global Solar, MiasoleWuerth Solar, Honda, Showa ShellG24i, Konarka04/10/23 5National Center for Photovoltaic Research and Education (NCPRE)

N-type

P-type

Eg: c-Si cell

N-type

P-type

Eg: CdTe, CIGS cell

Cell 1, Eg1

Cell 2, Eg2

Cell 3, Eg3

Eg1 > Eg2 > Eg3

N-type

P-type

Intrinsic, i, layer

Eg: a-Si:H cells

04/10/23 © IIT Bombay, C.S. Solanki 6

National Center for Photovoltaic Research and Education (NCPRE)

Homo-junction

Hetro-junction

P-i-N junction

Multi-junction

Junction is required to facilitate charge separation for PV operation

Eg: GaAs, a-Si cells

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Metallurgical grade Si (MGS)

InitialReaction Cholorosilan

es

Separation and

purification

Pure SiHCl3

Deposit solid Si

H2

Pu

re p

oly

-EG

S

EGS ingot

Grow single crystal

Si wafers

HC

l

Solid

Gas Gas

Solid

Liquid

Solid

QuarziteCoal +Liquid

Melting

Solid

Pu

re p

oly

-EG

S

Size of the c-Si cell is determined by the size of the ingot Shape of the c-Si is determined by the shape of ingot

04/10/23 © IIT Bombay, C.S. Solanki 8

Blocks can be manufactured easily in square shape Fits well in modules Low eff. of multi-crystalline material disappears at module level

04/10/23 © IIT Bombay, C.S. Solanki National Center for Photovoltaic Research and Education (NCPRE) 9

Mono-crystalline and Multi-crystalline Si substrates are grown

The substrate acts as absorber (of light) material

In thin film solar cells, the absorber layer is deposited Since the films are thin, a supporting substrate is required

Starting Wafer

c-Si process

Supporting substrate

Thin film process

Wafer Cutting

Wet Acidic Isotropic texturing

POCl3 Diffusion

Parasitic Junction Removal

PECVD SiNx:H ARC layer

Co-firing

Screen Printed Metallisation

Standard process

Solar cell performance: 12 - 16%

04/10/23 © IIT Bombay, C.S. Solanki National Center for Photovoltaic Research and Education (NCPRE) 11

EVA

Glass substrate

TCO

Absorber layer

Back metal

EVA

(a) Glass substrate with TCO

(b) Laser cut in TCO layer

(c) Deposition of absorber layer

(d) Laser cut in absorber layer

(e) Deposition of back metal contact

(f) Laser cut through metal and absorber layer

(g) Encapsulation with EVA

Monolithic interconnection of cells in modules

Laser cuts are used to define cell area

Chetan S Solanki, IIT Bombay ITM Expo, 7th March, 2009 12

in

scoc

P

FFIVEfficiency

• Efficiency is defined as the ratio of energy output from the solar cell to input energy from the sun.

IscI

Vm

Im

Pm

X

Voc

Power

2

2$

$

mWattm

WattCost

Production cost

Efficiency

Raw material cost, cell and module processing

Quality of material, technology understanding, cell size

Chetan S Solanki © Education Park, 2012 13

The annual production in 2012 was over 30,000 MWThe cost per Watt has come down to almost 1 $/Wp level

PV module product and cost

C-Si solar cell technology is dominant since its inception Thin film technologies likely to improve their share

Chetan S Solanki ©

Education Park, 2012

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Typical PV Wattage 1 MW to 100 MW

Electricity generated 4000 kWh to 40,000 kWh per day

1.5 Million units to 150 Million unit per

year

Where it can be used? Powering the grid, captive power plants, supplying peak load

Barrier for large scale implementation

Initial high cost, lack of bank fundingSuitability of grid, appropriate arrangement to sell electricity to govt.

Chetan S Solanki ©

Education Park, 2012

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Typical PV Wattage 1 kW to 100 kW

Electricity generated 4 kWh to 400 kWh per day

1500 unit to 150,000 unit per year

Where it can be used? Household electricity needs, industrial electricity, water pumping, academic campuses

Barrier for large scale implementation

Initial high cost, lack of awareness about Govt. policies, Bankers lack of awareness,Availability of product, local services

Chetan S Solanki ©

Education Park, 2012

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Typical PV Wattage 1 W to 10 W

Electricity generated 4 Wh to 40 Wh per day

1.5 unit to 15 unit per year

Where it can be used? Solar lamps, home lighting system, mobile charger

Barrier for large scale implementation

Initial high cost, lack of awarenessAvailability of product, local services

Chetan S Solanki ©

Education Park, 2012

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Typical PV Wattage 10mW to 1000 mW

Electricity generated 40 mWh to 4 Wh per day0.01 unit to 1.5 unit per year

Where it can be used? Calculators, toys, mobile charger A study solar lamp

Barrier for large scale implementation

No issue with calculators, toysSolar study lamp - Availability of product, local services

JNNSM launched in January 2010 NCPRE set up in October 2010 by MNRE as part of JNNSM 5 year Project Strong Education + Research thrust

www.ncpre.iitb.in

C-Si Lab Facilities

Plasma Enhanced CVD (PECVD)

Edge Isolation Tool

Diffusion Furnace

Quantum Efficiency Measurement System

Screen Printer

UV-Vis-NIR spectrometer

Corescan

Laser Doping System

Four Probe System

Carrier Lifetime Tester

RTP system

Solar IV characterization System

c-Si Solar Cell Fab Lab

Full fledged crystalline silicon solar cell fab pilot line of area 1800 sq feet was commissioned as part of NCPRE

Base line cell process is being developed

Solar Photovoltaics

Fundamentals, Technologies and

ApplicationsSecond Edition

Chetan Singh Solanki

Solar Photovoltaic Technology and SystemsA manual for Techicians, Trainers and Engineers

Chetan Singh Solanki

SOLAR PHOTOVOLTAICSA LAB TRAINING MANUAL

Chetan S SolankiBrij M AroraJuzer VasiMahesh B Patil