Spin-coated copper(I) thiocyanate as a hole transport layer for perovskite solar cells

Application of a low-cost and efficient p-type inorganic hole-transporting material, copper thiocyanate (CuSCN), on mesoporous n-i-p-configurated perovskite-based devices was conducted in this study. Diethylsulfide was chosen for the preparation of precursor solution in order to deposit CuSCN layer on perovskite without degrading it. Topographical, elemental, and electrical characterizations of spin-coated CuSCN layers were performed using XRD, AFM, SEM, XPS, UPS, and UV-Vis studies. A power conversion efficiency exceeding 11.02% with an open-circuit voltage of 0.83 V was succeeded in the perovskite solar cells under full sun illumination. Low-temperature solution process used for the deposition of CuSCN and a fast solvent removal method allowed the creation of compact, highly conformal CuSCN layers that facilitate rapid carrier extraction and collection. The differences in series and recombination resistances for CuSCN-free and CuSCN-containing cells were also determined using impedance spectroscopy (IS) analysis. Moreover, the effect of TiO2 layer thickness on the cell performance was studied where these TiO2 layers were used not only for electron extraction and transportation, but also as hole blocking layer in perovskite solar cells. The impedance spectroscopy results were also consistent with the differently configurated cell performances. This work shows a well-defined n-i-p perovskite cell with optimized layers which utilize low-cost and abundant materials for photovoltaic applications.