Band slope in CdS layer of ZnO:Ga/CdS/Cu2ZnSnS4 photovoltaic cells revealed by hard X-ray photoelectron spectroscopy

For compoundsemiconductorphotovoltaic cells with a common structure of the window-layer (WL)/buffer-layer (BL)/absorbing-layer (AL), the band slope in BLs, affecting the conversion efficiency, was directly and non-destructively measured byhard X-rayphotoelectron spectroscopy. We demonstrated that the band slope in CdS-BLs sandwiched between WLs and Cu2ZnSnS4 (CZTS)-ALs reflected the trend of the work functions of WLs (ϕWL). This result implies that the larger downward band slope to the WL can be achieved using a smallerϕWL. The relatively large downward band slope of ∼0.5 eV to the WL was estimated in our ZnO:Ga/CdS/CZTS sample with a higher conversion efficiency of 9.4%, which indicates that the conversion efficiency of CZTScells can be improved by a larger downward band slope to the WL.

Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: Keita Kataoka, Shin Tajima, Mitsutaro Umehara, Naoko Takahashi, Noritake Isomura, Kosuke Kitazumi and Yasuji Kimoto Source Type: research