No abstract

Perovskite films have emerged as candidates for light‐emitting diodes on accounts of excellent optical properties and low cost. Construction of quasi‐2D perovskite films by incorporating organic ammonium is an effective method to manufacture a pinhole‐free film with high photoluminescence quantum yield (PLQY). However, excess organic ammonium hampers carrier mobility through forming insulating capping layer and facilitates the formation of alow‐dimensional perovskite (n = 1 and n = 2) phase that accelerates non‐radiative recombination, resulting in poor performance of light‐emitting diodes. In this work, formamidine acetate is added into the quasi‐2D perovskite to modulate the optical and electrical properties of the perovskite films (CsFA‐Ac). Acetate ions are in favor of washing away excess ammonium and formamidine ions are beneficial to increase the formation energy of low‐dimensional (n = 2) phase. As a result, the quasi‐2D perovskite is transformed into 3D perovskite. The PLQY of the obtained CsFA‐Ac perovskite films is boosted to 59.9% and carrier mobility is enhanced to 47.3 cm2 V‐1 s‐1. Blue perovskite light‐emitting diode based on the CsFA‐Ac film is endowed with a prominent EQE of 8.8% (average 7.0%) at 477 nm. This work demonstrates a strategy for the development of efficient perovskite light‐emitting diodes.

Perovskite-based white-light-emitting devices (WLEDs) are expected to be the potential candidate for the next-generation lighting field due to their scalability and low-cost process. However, simple and adjustable WLED fabrication technology is in urgent need. Here, WLEDs with a single layer of perovskite quantum dots (PQDs) were constructed by combining Zn2+-doped CsPbBr3 PQDs with exciplex emission between poly­(9-vinylcarbazole) (PVK) and ((1-phenyl-1H-benzimidazol-2-yl)­benzene)) (TPBi). Zn2+-doped CsPbBr3 PQDs with polar ion shells were prepared by means of low temperature and post-treatment. The photoluminescence quantum yield (PLQY) can reach as high as 95.9% at the emission wavelength of 456 nm. The blue shift of its PL (∼60 nm) is much greater than that of other reported Zn2+-doped CsPbBr3 PQDs (5–10 nm), thus realizing the true blue-emission Zn2+-doped CsPbBr3 PQDs. As a result, just by controlling the thickness of TPBi, the adjustment of cold (CIE (0.2531, 0.2502)) and warm WLEDs (CIE (0.3561, 0.3562)) is realized for the first time.