[15a-2M-1~13] 13.10 Compound solar cells

▲ [15a-2M-11] The investigation of Ge incorporation effects in Cu₂ZnSnSe₄ thin-film solar cells (2)

〇(P)Kim Shinho¹, Kang Min Kim¹, Hitoshi Tampo¹, Hajime Shibata¹, Koji Matsubara¹, Shigeru Niki¹ (1.AIST)

Keywords:CZTGSe,kesterite thin-film solar cell,Ge incorporation

In this study, we investigated Ge incorporation effects in CZTSe thin film and its device. The Ge incorporated Cu₂ZnSnSe₄ (CZTGSe) thin films were prepared using a two-step process comprising co-evaporation of each element and a subsequent annealing step at various temperature in the range of 450–530 °C. Ge atoms were successfully incorporated into the Cu₂ZnSnSe₄ thin films, and the band-gap (E_g) of CZTGSe was controlled via the full Ge/(Sn+Ge) ratio range of 0–1. In addition, the annealing environment containing GeSe₂ led to CZTGSe thin films with flat surfaces, dense morphologies, and large grains comparable to their thickness. The highest efficiency achieved with the fabricated CZTGSe solar cells was 10.03%, with an open circuit voltage (V_OC) of 0.54 V. The E_g of absorption layer was controlled to 1.19 eV and its device exhibited an improved V_OC deficit (E_g/q − V_OC, q: electron charge) of 0.647 V, which is comparable to that of high-efficiency Cu₂ZnSn(S_xS_1−x)₄ solar cells.