Advances in Cu2ZnSnSe4 solar cell performance using 2SSS processing

We have developed an all-solid-state two-step process(2SSS) for fabrication of Cu
₂
ZnSnSe
₄
(CZTS) devices. Raman spectra are used to determine and control secondary phases and formation of excess MoSe
₂
at the CZTS/Mo interface due to over selenization. While processing at temperatures above 450 C decreases ZnSe and CuSe phases, a temperature driven interface recombination mechanism reduces Jsc and FF resulting in device efficiencies of 3%. Voc's, however are in the range 0.40-0.43 volts which are the same as for comparable band gap CIS and among the highest reported for CZTS.