Enhanced stability and performance of poly(4-vinylpyridine) modified perovskite solar cell with quaternary semiconductor Cu2MSnS4 (M= Co2+, Ni2+, Zn2+) as hole transport materials

In this work, highly stable and efficient perovskite solar cells (PSCs) in n-i-p configuration has been fabricated. Application of poly (4-vinylpyridine) (PVP) interlayer into the perovskite films via solution based process and quaternary semiconductor Cu2MSnS4 (M = Co2+, Ni2+, Zn2+) (CMTS) nanostructure particles as an inorganic hole transporting material (HTM), result in modified perovskite surface and improving the long term stability and the photovoltaic parameters of the PSCs. The power conversion efficiency (PCE) of the record device with Cu2ZnSnS4(CZTS) HTM and PVP interlayer reaches 13.57%, Voc gains 1.03 V, fill factor (FF) increases up to 70.64% and the device demonstrates low hysteresis (4.14%). Photoluminescence (PL), absorption spectra, electrochemical impedance spectroscopy (EIS) and FESEM images reveal that, the interface between PVP and inorganic CMTS nanostructure particles favorably can reduce non-radiative recombination and enhance Voc. In addition, the presence of hydrophobic PVP interlayer and CMTS nanostructure particles capping with PVP ligands prevent the ingress of the moisture in to the perovskite layer and result in improved stability, where the devices based on CZTS HTM, retain 97% of the initial efficiency after 30 days at room temperature and 35–40% relative humidity.