Additives in halide perovskite for blue light-emitting diodes : passivating agents or crystallization modulators?

Abstract

Successful adoption of defect management and carrier confinement strategies in Ruddlesden-Popper (RP) perovskites has driven the impressive improvements to performance of perovskite-based light-emitting diodes (PeLEDs) seen to date. Although functional additives have been advantageous in mitigating defects, their influence over crystallization behavior of RP (L2Am-1PbmX3m+1) perovskites has yet to be fully studied. This is especially important for blue-emitting mono-halide RP perovskites, where stringent control over m domain distribution is needed for efficient PeLEDs. Herein, we investigate the effect of tri-phenyl-phosphine-oxide (TPPO) on crystallization behaviour of blue RP (PBA2Csm-1PbmBr3m+1) perovskites. Despite TPPO addition, its absence in the resulting film eliminates its role as a passivating agent. Instead, TPPO acts as crystallization and phase distribution modulator – promoting the formation of a narrow distribution of higher m domains with higher Br content. In doing so, an enhancement of ~35% was noted with champion device yielding efficiency of 3.8% at λ of 483 nm.