Iodoplumbate Complex Transformation for Efficient Perovskite Emitters

High-quality, low-defect perovskite emitters are crucial for achieving high-performance perovskite optoelectronics. Additive engineering, which involves incorporating organic molecules (predominately amino-based) into perovskite precursor solution, is an effective strategy for reducing perovskite defects and thereby achieving high-quality perovskite films. Many efforts have been made to identify suitable additives and to elucidate their roles in defect suppression. However, to date, the lowest trap density of 3D perovskite films is ≈10¹³ cm^-3, which continues to constrain the enhancement of photoluminescence quantum efficiency (PLQE). Hence, unveiling the mechanisms of defect formation and further reducing trap-assisted nonradiative recombination, and consequently enhancing the PLQEs of 3D perovskite films, remains a significant challenge. Through in situ monitoring of the perovskite crystallization process, it is revealed that 3D perovskites retain numerous defects due to incomplete conversion of iodoplumbate complexes. The effectiveness of non-amino additives containing ester and ether groups is emphasized in promoting the complete conversion of iodoplumbate complexes prior to nucleation, thereby eliminating defect formation. As a result, high-quality 3D perovskites are obtained, exhibiting a trap density of 4.8 × 10¹² cm^-3 and a peak PLQE of 84.5%. Consequently, near-infrared perovskite light-emitting diodes with an impressive external quantum efficiency of 26.5% are realized.