Abstract：
Although metal halide perovskites (MHPs) have demonstrated remarkable external quantum efficiencies (EQEs) in red and green light-emitting diodes (LEDs), the blue ones confront efficiency and stability problems due to the high defect density in the perovskite films. Large amounts of defect passivation strategies are successfully developed to improve the device performance. Nevertheless, the influence of the molecular configuration of the passivators on the perovskite crystallization process has not been comprehensively investigated so far. Here, we investigate the effect of the phenyl ring on the perovskite crystallization dynamics and the passivation effect. The additive with a phenyl ring performs the π-π stacking ability with phenethylammonium (PEA+) molecules, resulting in a deteriorated crystallinity and a weakened passivation ability. Conversely, the additive without the phenyl ring is helpful to promote the participation of PEA+ molecules in the crystalline process, leading to a higher crystallinity and a stronger passivation effect. As a result, the EQE of the blue perovskite LED has increased from 4.72 to 11.06% by using the phenyl ring-free additive. Therefore, it is advisible to develop the conjugated nonplanar additives in the PEA+-assisted quasi-two-dimensional perovskites. This finding may enlighten the rational design of defect passivators for highly efficient perovskite LEDs.
摘要：
尽管金属卤化物钙钛矿（MHP）在红色和绿色发光二极管（LED）中表现出了显着的外量子效率（EQE），由于钙钛矿薄膜中的高缺陷密度，蓝色薄膜面临效率和稳定性问题。成功开发了大量的缺陷钝化策略以提高器件性能。然而，到目前为止，钝化剂的分子构型对钙钛矿结晶过程的影响尚未得到全面研究。这里,我们研究了苯环对钙钛矿结晶动力学和钝化效果的影响。具有苯环的添加剂与苯乙基铵（PEA）分子具有π-π堆叠能力，导致恶化的结晶度和削弱的钝化能力。相反，无苯环的添加剂有助于促进PEA+分子参与结晶过程,导致更高的结晶度和更强的钝化效果。因此,通过使用无苯环添加剂,蓝色钙钛矿LED的EQE从4.72%增加到11.06%。因此,可以在PEA辅助的准二维钙钛矿中开发共轭非平面添加剂。这一发现可能会启发高效钙钛矿LED的缺陷钝化剂的合理设计。
