Efficient Organic Photovoltaics Enabled by Aqueous Ammonia-Based Doped Copper Thiocyanate Hole Transport Layer

The efficiency of organic photovoltaics (OPVs) has been significantly increasing over the past few years, primarily due to the advent of new active layer materials and carrier-selective charge transport interlayers. Many recent research efforts are currently directed toward developing hole transport layers (HTLs) to replace (PEDOT:PSS), which is still broadly utilized as HTLs for standard structure OPVs. Despite the promising features of PEDOT:PSS, the high acidity of the PSS chain is known to compromise the stability of the devices. To address this issue, we propose alternative HTL materials. This study uses copper (I) thiocyanate (CuSCN) prepared from aqueous ammonia solvent as the HTL in efficient nonfullerene-based OPVs. To further increase the efficiency of the CuSCN-based OPVs, we also explore the possibility of adding copper (II) chloride (CuCh) inorganic salt dopant into the CuSCN solution.