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

Hybrid perovskites are emerging as highly efficient materials for optoelectronic applications, however, the operational lifetime has remained a limiting factor for the continued progress of perovskite light emitting devices such as light emitting diodes (LEDs) and perovskite light emitting electrochemical cells (PeLECs). In this work, PeLECs utilizing an optimized fraction of LiPF6 salt additive exhibit enhanced stability. At 0.5 wt% LiPF6, devices exhibit 100 h operation at high brightness in excess of 800 cd/m2 under constant current driving, achieving a maximum luminance of 3260 cd/m2 and power efficiency of 9.1 Lm/W. This performance extrapolates to a 6700 h luminance half-life from 100 cd/m2, a 5.6-fold improvement over devices with no lithium salt additive. 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 degradation of luminance with decreased current. These losses are mitigated by LiPF6 addition, an effect postulated to arise from preservation of perovskite structure. To further understand lithium salt addition, electrochemical impedance spectroscopy with equivalent circuit modeling is performed. Electrical double layer widths from ionic redistribution are minimized at 0.5wt% LiPF6 and inversely correlate with efficient performance.