Fabrication of top down Cu2ZnSnSe4 thin film solar cells with Cd-free buffer layer by plasma-assisted molecular beam epitaxy

• Main Authors: Guan-he Chen, 陳冠合
• Other Authors: Chu-shou Yang
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/yw43ez

碩士 === 大同大學 === 光電工程研究所 === 102 === The upside down Cu2ZnSnSe4 (CZTSe) thin film solar cell device is grown on soda lime glass substrate by plasma-assisted molecular beam epitaxy (PA-MBE). The solar cell uses CZTSe as absorber-layer, cadmium-free buffer layer (ZnSe:Ga), and transparent conducting oxide (TCO) ZnSnO (ZTO). Since the growth temperature of ZTO fit at high temperature for high quality and CZTSe suit at low temperature, the traditional manufacturing process was upside down to avoid broking the absorber properties. The first layer is TCO, and the second is buffer layer and absorber layer, the final is metal back electrode, and all of those are the structure of device. We analyze the solar cell device layer by layer. The ZTO thin films are grown on c-Al2O3 (c-sapphire) and soda lime glass. In X-ray diffraction (XRD) spectra, the crystal structure can be obtained that both of grown on c-sapphire and soda lime glass are amorphous. Additionally, we found that the average roughness of grown on glass was 0.9 nm and c-sapphire was 1.5 nm. According to four-point Hall measurement, the resistivity of ZTO grown on glass is smaller than c-sapphire. With the result, we chose glass as substrate for this solar cell. The lowest resistivity and highest electron concentration of ZnSe:Ga grown on ZTO are1.16 x10-2 Ω-cm and 1.58x1020 (cm-3), respectively.