Thin film solar cells, Crystalline silicon solar cells, Organic material solar cells and Novel cell technologies 

Thin Film Solar cell technology, which previously had been utilized in calculators and other handheld devices, are now extensively used in power plants, BIPV and Vehicle Charging systems. Thin Film Solar Cells (TFSC) are formed by depositing nanometer to micrometer thickness of photovoltaic materials on variety of substrates like glass, steel or polymer.

Compound Photovoltaic materials that are used for depositing as thin films are combination of Group-XI (Cu, Ag, Au),Group-XII (Al, Ga, In) or Group-XVI (S, Se, Te) elements from periodic table. CIS/CIGS/CGS are various combinations that can be compounded from I-III-VI semiconductor to produce band gap of 1.0-1.7eV. CdTe (Cadmium Telluride) solar cells are comparatively higher efficient than other thin film and cheaper than crystalline-Si in the market. Although cheaper, thin film solar cells are limited by low efficiency and hazardous toxicity of Cadmium that questions the environment-friendliness of the solar technology on the whole.

Silicon based thin films are deposited using either black silicon or amorphous silicon. Amorphous silicon hydrogenated with carbon from carbides that increase optical efficiency of cells, and thin film character can be used to roll and form p-type, n-type and other electronic devices. Nano-crystalline silicon is more flexible film and has higher light absorbing property which does not require direct normal irradiance and can work in diffused irradiations too.

Crystalline solar cells are highly efficient than thin film cells but they are more process intensive techniques. Monocrystalline Silicon is obtained on refining and growing ingots from high purity single crystal Silicon using Czochralski Process. Polycrystalline cells are easy to manufacture than monocrystalline which saves extra refining that is must needed in mono-crystalline cell production. Spherical Solar cells are much newer technology. Spherical solar are marketed under the brand Sphelar. Solidified Silicon drops are obtained in zero-gravity environment, measuring 1.8mm diameter are highly transparent and embedded in transparent solar cell window glass that can absorb light incident from any direction. They allow interconnection in both series and parallel configurations.

Organic Thin Films are obtained by mutating molecular structure of functional group polymers through chemical proceses which results in high optical absorption coefficient. Through vacuum thermal evaporation of different polymers, single layer, bilayer, heterojunction and morphed-heterojunction depositions are obtained. Dye sensitized solar cells are obtained using organic dyes and inks acting as electrolytes that are sandwiched between photo-electrode and catalytic-electrodes. This is comparatively cheaper technology that can be customized to varied light sensitivities.

Latest cell manufacturing technologies are HIT (Hetero-juntion with Intrinsic Thin layer) and Tandem technologies. HIT comprises of single thin layer of crystalline Silicon sandwiched between ultra-thin layers of amorphous silicon. Due to this the band gap is optimally placed at photo-sensitive energy level and hence has higher conversion efficiencies. They have better performance even at higher temperatures. Tandem cells are formed from thin layers of amorphous silicon and thicker layers of micro-crystalline silicon. This is very research intensive study in tandem cells to overcome some limitations like top cell transmittance, textured substrates and optimization to varying solar spectrum throughout the day.  Efficiencies have been increased drastically by focusing on Material preparation, physical, optical and electronic characterization, Simulation, Modeling and Device fabrication Techniques.

Design of Solar Power Plants, nowadays, is integrated with oother power generating resources and produce hybrid technolgies. More details on Solar-Hybrid technology is available here. Other than Hybrid, major technology options for setting up Solar Power Plants is available here.