One or more PV solar cell materials are deposited on the substrate, which is called amorphous silicon. Figure 2.3 shows amorphous silicon photovoltaic solar cell. Vapor depositing technology is used to deposit 1-micrometer silicon materials on substrate (glass or metal). Depositing temperature is upto 75°C for plastic material as substrate. One of major drawbacks is, when exposed to sunlight, degradation has been happened in their output power. Electric field strength is to be increased when thickness of material reduced [3, 26]. Unisolar is a company which inventing solar PV cells using silicon thin film. The three-layer system can be used to optimize absorbing sun light from solar spectrum.
Table 2.2 Second-generation PV cells.
| Manufacturer | Country | Technology |
| Amysolar | France | Amorphous silicon |
| 3sun | Italy | Amorphous silicon |
| Anwell Precision | Hong Kong | Amorphous silicon |
| EcoMedia | Italy | Cadmium sulfide/cadmium telluride |
| Dupont | United States of America | Copper indium gallium diselenide |
| Nexcis | France | Copper indium gallium diselenide |
| First Solar | United States of America | Copper indium gallium diselenide |
Figure 2.3 Amorphous silicon PV cell.
2.3.2 Cadmium Telluride PV Cell
Cadmium telluride is a thin layered film semiconductor, which is used to convert receiving solar light into electrical energy [25]. The cadmium PV solar cell consists of two layers, which are top and bottom layers; the bottom layer is made up of carbon paste and top layer is made up of cadmium built stannous oxide or tin oxide, which is shown in Figure 2.4. Cadmium telluride is located between the top layer and semiconductor. The cadmium telluride-based solar PV cells are the second highest technology available in the market after the crystalline silicon. Among the different types of solar PV cells available in the world market nearly 7% is cadmium telluride.
Figure 2.4 Cadmium telluride PV cell.
The major advantages of this type of solar PV cells are time and cost for manufacturing is lower, and it can also be replaced by conventional silicon PV technologies. In total production, 21.5% of cadmium telluride–based PV cells are fabricated by First Solar, and its efficiency is 14.7% [13].
2.3.3 Copper Indium Gallium Diselenide PV Cells
The copper indium gallium diselenide PV cells have higher energy generated capacity compared to any other solar PV cell technology, which is shown in Figure 2.5. Power production rate on glass substrate increased upto 20%. Recent advancement in solar PV cells is PV devices and metal or polyamide as substrate. It can be applicable in space application due to its advantages like flexibility, opposing to solar radiation and maximum specific power. It is having highest solar light absorbing coefficient, and band width is 15 eV [15].
2.4 Third-Generation PV Cells
Third-generation PV cells’ objective is to use very thin film for power production compared to second-generation PV cells. Different manufacturers of third-generation photovoltaic cells are listed in Table 2.3. The perception is to do diminish the cost per watt peak with small intensification of areal cost. Availability of raw material is higher and being harmless is the basic requirement; it common for both second and third generation. Third-generation solar PV cells are very much suitable for mass production. This type of PV cells is not giving as much efficiency and quality of single crystal PV cells [10].
Figure 2.5 Cadmium indium gallium diselenide PV cell.
Table 2.3 Third-generation PV cells.
| Manufacturer | Country | Technology |
| Amo Solar | Korea | Dye Sensitized |
| Bloo Solar | United States of America | Copper zinc tin sulfide |
| G24 Power | United Kingdom | Dye Sensitized |
| Heliatek | Germany | Organic Polymer |
| Samsung Electronics | Korea | Dye Sensitized |
| Solar Ivy | Unites States of America | Organic Polymer |
| Solterra Renewable | Unites States of America | Quantum Dot |
| Timo Technology | Korea | Dye Sensitized |
| Voxtel | Unites States of America | Quantum Dot |
2.4.1 Copper Zinc Tin Sulfide PV Cell
Copper