Enhanced Operational Stability of Perovskite Light-Emitting Electrochemical Cells Leveraging Ionic Additives

Hybrid perovskites are emerging as highly efficient materials for optoelectronic applications, however, their operational lifetime has remained a limiting factor for their continued progress. In this work, perovskite light emitting electrochemical cells utilizing an optimized fraction of lithium hexafluorophosphate (LiPF6) salt additive exhibit enhanced stability. At 0.5 wt% LiPF6, devices exhibit 100 h operation at high brightness in excess of 800 cd m(-2) under constant current driving, achieving a maximum luminance of 3260 cd m(-2) and power efficiency of 9.1 Lm W-1. This performance extrapolates to a 6700 h luminance half-life from 100 cd m(-2), a 5.6-fold improvement over devices with no LiPF6. Analysis under constant voltage driving reveals three current regimes, with lithium addition strongly enhancing current in the second and third regimes. The third regime correlates lower rates of luminance with lowered current flow. These losses are mitigated by LiPF6 addition, an effect postulated to arise from preservation of perovskite structure. Electrochemical impedance spectroscopy with equivalent circuit modeling reveals that electrical double layer widths are minimized at 0.5 wt% LiPF6 and inversely correlated with efficient performance. These results demonstrate that an optimal LiPF6 concentration improves stability and efficiency through improved double layer formation and retention of perovskite structure.