High‐Efficiency Nondoped White Organic Light‐Emitting Diodes Based on All‐Exciplex Emission

Abstract

A nondoped full‐exciplex approach is applied in white organic light‐emitting diodes (WOLEDs). Both the blue emission and yellow emission are from exciplex, which makes it possible to exceed the 25% internal quantum efficiency limit of normal fluorescent OLEDs via reverse intersystem crossing from triplet to singlet states because of the small energy gap between them. White emission can be realized by simply stacking the blue and yellow exciplex materials because the same acceptor material is used in the emitting systems. And a two‐color WOLED with an external quantum efficiency (EQE) of 6.11% is demonstrated, exceeding the efficiencies of the exciplex‐based blue and yellow monochrome devices. The higher efficiency is attributed to redistribution of the exciplex excitons, which suppresses the exciton concentration quenching at the emission interface. By adopting a quantum‐well‐like structure, the EQE can be further improved. This approach sheds light on the simple fabrication of high‐efficiency WOLEDs in the future.

Recombination of X-ray-Generated Radical Ion Pairs in Alkane Solution Assembles Optically Inaccessible Exciplexes from a Series of Perfluorinated para-Oligophenylenes with N,N-Dimethylaniline

“…Exciplex generation is an enormous and thoroughly studied field in photochemistry [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and, to a lesser extent, in electrochemistry [26][27][28][29][30][31][32][33][34], with its established detailed reaction schemes and experimental protocols. Further important, more recent extensions here are the already mentioned use of exciplexes for optimizing emitters in OLEDs [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] and the quantitative rationalization of exciplexes in quantum chemical calculations [52][53][54][55]…”