Design optimization of CdTe thin film solar cells from numerical analysis

In this paper, a modified structure for CdTe thin film solar cell was proposed by numerical analysis with an addition of a novel ZnO buffer to improve the conversion efficiency. The CdS window layer was reduced to 50 nm together with the insertion of zinc oxide (ZnO) as the buffer layer to prevent forward leakage current. The thickness of CdTe absorber layer was varied from 1000 nm to 5000 nm and as well as the operating temperature was also varied from 25°C to 165°C. The numerical simulation was done by Analysis of Microelectronic and Photonic Structures (AMPS-1D) simulator. The highest conversion efficiency obtained was 20.27% (Voc = 1.08 V, Jsc = 24.93 mA/cm², FF = 0.83) with 5000 nm CdTe absorber layer and 50 nm CdS window layer. Moreover it was observed that with the increase in operating temperature, the normalized efficiency decreased linearly at a gradient of 0.2%/°C, which reveals that the CdTe thin film solar cell has higher stability.