Mitigating the detrimental effects of joule heating for perovskite light emitting diodes

Metal halide perovskites are promising materials for next generation light emitting diodes, with external quantum efficiency (EQE) over 20% been demonstrated. However, the device stability and the EQE roll-off of perovskite light emitting diodes are currently far from satisfactory, and joule heating was claimed to be one of the main causes. In this work, by replacing the commonly reported TPBi electron injection layer, we significantly reduce the device driving voltage and thus heat generation. This leads to remarkably improved EQE roll-off and device stability. Moreover, while injection layers like TPBi often inhabit charge injection at cryogenic temperatures, the charge injection is barely affected in our new device stack, enabling us to understand the device behavior at such low temperatures and we can further mitigate the joule heating effects by cooling down the devices. Our new stack provides EQE of over 10% at 300 mA/cm2 and a record lifetime of T70 = 50 h at 100 mA/cm2 at RT.