Additives in Halide Perovskite for Blue-Light-Emitting Diodes: Passivating Agents or Crystallization Modulators?

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 (L(2)A(m-1)Pb(m)X(3m+1)) perovskites has yet to be fully studied. This is especially important for blue-emitting monohalide RP perovskites, where stringent control over m domain distribution is needed for efficient PeLEDs. Herein, we investigate the effect of triphenylphosphine oxide (TPPO) on crystallization behavior of blue RP (PBA(2)Cs(m-1)Pb(m)Br(3m+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 similar to 35% was noted with the champion device yielding efficiency of 3.8% at lambda of 483 nm.