Efficient Light-Emitting Diodes Based on Nanocrystalline Perovskite in a Dielectric Polymer Matrix

• Published in: Nano letters Vol. 15; no. 4; pp. 2640 - 2644
• Main Authors: Li, Guangru, Tan, Zhi-Kuang, Di, Dawei, Lai, May Ling, Jiang, Lang, Lim, Jonathan Hua-Wei, Friend, Richard H, Greenham, Neil C
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 08.04.2015
• Subjects: Blends; Bypasses; Devices; Electroluminescence; Light-emitting diodes; Nanocrystals; Perovskites; Quantum efficiency; perovskite nanocrystals; Perovskite light-emitting diode; perovskite-polymer blend; perovskite morphology
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.5b00235

Electroluminescence in light-emitting devices relies on the encounter and radiative recombination of electrons and holes in the emissive layer. In organometal halide perovskite light-emitting diodes, poor film formation creates electrical shunting paths, where injected charge carriers bypass the perovskite emitter, leading to a loss in electroluminescence yield. Here, we report a solution-processing method to block electrical shunts and thereby enhance electroluminescence quantum efficiency in perovskite devices. In this method, a blend of perovskite and a polyimide precursor dielectric (PIP) is solution-deposited to form perovskite nanocrystals in a thin-film matrix of PIP. The PIP forms a pinhole-free charge-blocking layer, while still allowing the embedded perovskite crystals to form electrical contact with the electron- and hole-injection layers. This modified structure reduces nonradiative current losses and improves quantum efficiency by 2 orders of magnitude, giving an external quantum efficiency of 1.2%. This simple technique provides an alternative route to circumvent film formation problems in perovskite optoelectronics and offers the possibility of flexible and high-performance light-emitting displays.