Recently, the compound thin film solar cell group of IEECAS makes a significant progress on polycrystalline CdTe solar cells. The conversion efficiency of 2 μm thickness CdTe solar cells prepared on cheap commercial glass reaches 14.4%, a significant increase from 12.78%, set in 2012. The conversion efficiency has been certificated by Photovoltaic and Wind Power Systems Quality Test Center, Chinese Academy of Sciences (CAS). This means IEECAS have made important progress on CdTe solar cells.
CdTe is a direct energy band gap (Eg) semiconductor with Eg of 1.45 eV at room temperature, which closely matches the peak of the solar spectrum. CdTe is quite stable because only the stoichiometric CdTe compound can be formed at temperature higher than 300 ℃. Its optical absorption coefficient is in the range of 104-105 cm-1. Thus, a CdTe thin film with a thickness of 2 µm will absorb nearly 100% of the incident solar radiation above its band gap, greatly decreasing the material need referring to Si solar cells. CdTe solar cells also have advantage of short production cycle, low cost, and suitable for mass production. Therefore, the CdTe solar cells attract scientific research and industry attention because of its high conversion efficiency, low cost, and high stability.
Feb. 2014, Solar Cells, Inc. sets a new world record for CdTe photovoltaic (PV) solar cell efficiency, reaching 20.4%. First Solar's new CdTe research cell conversion efficiency matches the research cell efficiency record of multicrystalline silicon. March 2014, First Solar revealed a new total area module efficiency record for CdTe solar cells of 17%. Now, the CdTe solar cells is the lowest PV technology, only $0.55/Wp. But its mass production technology has been monopolized by a few businesses in the Unite State. In additional, the highest efficiency of CdTe solar cells prepared by the low temperature magnetron sputtering technique is 14.5%, achieved by the Toledo university.
By using the equipments and raw materials made in China, the Institute of Electrical Engineering, CAS achieves 14.4% efficiency without high resistive layer, showing we also can achieve the high efficiency CdTe solar cells as long as we master the key technology. This provides the basis research for CdTe thin film solar cells research and industrialization in China, which will enable China's long industry development in CdTe solar cells.
