Antisolvent treatment of copper(i) thiocyanate (CuSCN) hole transport layer for efficiency improvements in organic solar cells and light-emitting diodes

Abstract

Copper(I) thiocyanate (CuSCN) has been widely used as a hole-transport layer in organic optoelectronic devices. However, being a coordination polymer, its solution-processing is not straightforward; the typical process requires sulfide-based solvents that strongly interact with Cu(I). Herein, we show that a simple step of washing the CuSCN HTL with antisolvents, specifically acetone (Ace) or tetrahydrofuran (THF), can significantly increase the short-circuit current (J_sc) and fill factor (FF) of organic photovoltaic (OPV) cells. The treatment leads to an increase in the average power conversion efficiency (PCE) from 8.18% for OPV devices based on untreated CuSCN to 9.16% and 9.25% for cells based on Ace- and THF-treated CuSCN HTL, respectively. Furthermore, for organic light-emitting diodes (OLEDs) based on CuSCN HTL, the treatment by THF also increases the external quantum efficiency (EQE) from 5.2% to 8.2%. The facile antisolvent treatment can be readily applied to the solution-processing of CuSCN which is already employed in various organic optoelectronic devices.