Introduction to solar cells

PV Materials

Si: monocrystalline, polycrystalline, and amorphous

III-V semiconductors: GaAs and InP

II-VI and I-III-VI: CdTe and CuIn1-xGaxS1-ySey(CIGSS)

Organic materials: dyes, polymers, and small molecules

Classification of PV Devices

Depending on the evolution

First generation (crystalline solar cells)

Si solar cells

III-V GaAs solar cells

Second generation (thin film solar cells)

CIGS-based

CdTe

a-Si

Third generation

Novel ideas for high-efficiency cells

One dichotomy is based on the thickness of the semiconductor

Crystalline solar cells-cells are relatively very thick on the order of

200-500µm

Thin film semiconductor-cells are relatively very thin f size ranging 1-

10 µm

Depending upon the type of absorbing material used, manufacturing

technique / process adopted, and type of junction formed etc., the solar cell

technologies can be broadly classified as following.

As described by the Bube (1998), there is a family tree of PVs based

on the size of these crystals

Single crystalline - the dominant silicon technology.

Multicrystalline- in which the cell is made up of a number of relatively

large areas of single crystal grains, each on the order of 1mm-10cm in size

Polycrystalline- grains have the dimension of the order 1 µm to 1mm

Microcrystalline- cells with grain sizes less than 1 μm

Amorphous-in which there are no single-crystal regions, as in amorphous

silicon (a-Si).

Photovoltaic Cells

Single crystal

Multi crystalline

PolyCrystalline

MicroCrystalline Amorphous

Another way to categorize photovoltaic materials is based on whether

the p and n regions of the semiconductor are made of the same material

(with different doping, of course)

Photovoltaic Cells

HomojunctionPhotovoltaic

Cells

HeterojunctionPhotovoltaic

Cells