Spiro-OMeTAD with a 1,4-Benzenedithiol Additive to Promote High-Performance Perovskite Solar Cells

Small molecule material spiro-OMeTAD is widely employed as the hole transport layer (HTL) in efficient n-i-p perovskite solar cells (PSCs). However, the intrinsic poor conductivity and hole mobility of spiro-OMeTAD, coupled with its strong hygroscopic nature, severely limit the performance and lifetime of the devices. Herein, we employ a low-cost 1,4-benzenedithiol (BDT) additive to overcome the limits of pristine spiro-OMeTAD. BDT doping in spiro-OMeTAD can increase the carrier mobility and electrical conductivity. Meanwhile, because of the sulfhydryl group in BDT, the hygroscopic nature of spiro-OMeTAD is decreased. Furthermore, the trap-state density and defect-induced nonradiative recombination of the BDT-doped device are decreased. Additionally, the improved energy level alignment between the HTL and the perovskite layer facilitates more efficient hole transport. Consequently, the rigid PSC and flexible PSC doped with BDT achieve champion power conversion efficiencies (PCEs) of 22.34% and 21.04%, respectively, surpassing the PCEs of 20.83% and 19.64% obtained from the original rigid PSC and flexible PSC, respectively. Furthermore, the BDT-based devices exhibit better stability than control devices.