A new co-solvent assisted CuSCN deposition approach for better coverage and improvement of the energy conversion efficiency of corresponding mixed halides perovskite solar cells

In this research, inorganic copper thiocyanate (CuSCN) hole transport layer (HTL) was applied in conventional structure of perovskite solar cells (PSCs). Besides, mixed halides perovskite (Cs_0.05(MA_0.17FA_0.83)_0.95Pb(I_0.83Br_0.17)₃) was utilized as the light absorbing layer and deposited on FTO/compact TiO₂ substrates through a one-step coating method in ambient condition. The mentioned perovskite is more stable against high temperature, high irradiation and humidity compared to commonly applied MAPbI₃ perovskite. Nevertheless, the CuSCN could not be well dissolved in usual dipropyl sulfide solution and should be deposited for several times to achieve suitable thickness, this could reduce the quality of CuSCN layer and corresponding interfaces with the other layers. Here, Acetonitrile was applied as a co-solvent to increase the CuSCN concentration in mixed solvent. Consequently, the proper thickness was achieved for just one step of spin coating process. In addition, the CuSCN layer seemed smooth and pinholes free and the interfaces were well-formed. The PSCs with CuSCN HTLs prepared by usual low concentration CUSCN solution were also fabricated and characterized. The results show that the PSCs with improved CuSCN layer deposited from the acetonitrile assisted solution demonstrated a power conversion efficiency (PCE) 11%. This value was nearly close to that of the reference cell with Spiro-OMeTAD organic HTL. The corresponding stabilities were also comparable according to the carried out measurements. In addition, the PCE was increased about 45% compared to the optimized situation of the PSCs with CuSCN layer prepared from low concentration CuSCN solution.