Photovoltaic performance of planar CH3NH3PbI3 perovskite solar cells based on CdS and high transmittance Cd(S,O) electron transport layers stacked with ZnO hole blocking layer

Abstract

The chemical bath deposited n-type CdS and Cd(S,O) layer were implemented as electron transport (ET) layers integrated with ZnO hole blocking (HB) layer in the fabrication of planar CH3NH3PbI3 (MAPbI3) perovskite solar cells (PSC). The bonding environment and native defect structure of CdS and Cd(S,O) ET layers were established by Raman and photoluminescence spectral analysis. Optical studies showed that Cd(S,O) has higher UV–Vis transmittance and band edge threshold relative to CdS of similar thickness. The photovoltaic performance of the solar cells evaluated with CdS and Cd(S,O) ET layers of different 40-, 55-, and 80-nm thickness shows the effect of light intensity at the MAPbI3 photoabsorber and establishes the importance of native defects in electron extraction and transport in determining photoconversion efficiency (PCE). The effect of defect states in CdS and Cd(S,O) over corresponding J–V curves and fill factor of PSC device are described in terms of an energy band model. For 40-nm-thick Cd(S,O)/ZnO (ET/HB) layer, a PCE of 11.1% was achieved and compared with 9.18% for the CdS/ZnO (ET/HB) layer.