Universal performance improvements in CuSCN-based devices enabled by CuBr2 doping: Transistors, solar cells, and photodetectors

Copper(I) thiocyanate (CuSCN) has become one of the standard hole-transport layers (HTLs) for an ever-expanding range of device applications. However, solution-processed CuSCN films suffer from hole-trapping SCN − vacancies (V SCN ) and limited p-type conductivity. Herein, we show that doping CuSCN with copper(II) bromide (CuBr 2 ) can deliver dual functions of defect-healing and p-doping, greatly improving the hole-transport properties. Applied as a p-channel in thin-film transistors, the field-effect hole mobility is increased by 8-fold up to 0.08 cm 2 V −1 s −1 while crucially keeping a low off-current, unlike previous p-doping attempts. Further, CuBr 2 -doped CuSCN exploited as an HTL in organic solar cells improves charge collection and reduces trap-assisted recombination, pushing power conversion efficiency from ~16% up to 18.3%. Remarkably, the same HTL yields outstanding performance for single-component near-infrared (NIR) organic photodetectors, an emerging simple device structure based solely on organic acceptor as the photoabsorber. CuBr 2 doping effectively suppresses the dark current and improves all device metrics, achieving a specific detectivity of ~10 12 Jones at 840 nm and a cut-off frequency up to 560 kHz. The universal device performance improvements demonstrate the synergistic benefits of combined defect-healing and p-doping effects of CuBr 2 and further highlight CuSCN as a promising HTL for emerging device applications.