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A Comparative Study via Photophysical and Electrical Characterizations on The Interfacial and Bulk Exciplex-Forming Systems for Efficient Organic Light-Emitting Diodes
摘要： An efficient organic light-emitting diode (OLED) based on BCzPh:CN-T2T exciplex as emitting layer (EML) has been fabricated by exploiting the charge balance and favorable molecular orientations. To further understand the details of the exciplex-forming mechanism, time-resolved photoluminescence (TRPL), capacitance-voltage (CV), impedance spectroscopy (IS), and transient electroluminescence (EL) measurements were used to probe the photophysical and electrical characteristics of EL devices incorporating interfacial- (BCzPh/CN-T2T) and bulk- (BCzPh:CN-T2T) exciplex as emitting layer. The interfacial- and bulk-exciplex devices reveal maximum external quantum efficiency (EQE) of 7.7% and 26.4%, respectively. The reason for different device performance was rationalized by comparing the amount of charge density accumulated at the EML’s interface responsible to exciplex emission. In addition, the TRPL measurement monitored from short to long wavelength was used to explore the harvest of non-radiative triplet back to singlet via reverse intersystem crossing as well as to examine the efficiency of delayed fluorescence. The bulk-exciplex system showed a distinct delayed fluorescence as compared to that of the interfacial one, which was also corroborated by the observation in the transient EL. The result indicates that bulk-exciplex can reduce the accumulated charge in EML rapidly, resulting in the improvement of EL efficiency. This assumption was further verified by the CV and IS measurements. Our results reveal that the accumulated charge density as well as the bulk resistance of the bulk-exciplex device are much lower as compared to those of the interfacial counterpart device.
关键词： transient photoluminescence,impedance spectroscopy,Interfacial exciplex,transient electroluminescence,bulk exciplex
更新于2025-09-23 15:19:57
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High-performance white organic light-emitting diodes with doping-free device architecture based on the exciton adjusting interfacial exciplex
摘要： White organic light-emitting diodes (WOLEDs) with doping-free device architecture have aroused more attention due to their attractive merits such as simplified fabrication procedures and reduced costs. However, the electroluminescence performance of that is still manifestly unsatisfactory and needs to be further improved. Here, high-performance doping-free two-color and three-color WOLEDs with the accurate manipulation of excitons have been successfully fabricated by optimizing the interfacial exciplex. As a result, two-color WOLEDs exhibit the controllable electroluminescence spectra with a wide correlated color temperature (CCT) spanning from 2878 to 9895 K at the voltage of 4 V, as well as the maximum forward-viewing power and current efficiencies of 83.2 lm W?1 and 63.3 cd A?1, respectively. The three-color WOLED not only realizes the maximum efficiencies of 50.1 lm W?1 and 44.7 cd A?1, but also exhibits superior color stability with a color rendering index of 86, a CCT of 2679 K, and a Commission International de I’Eclairage coordinates of (0.49, 0.46) at the voltage of 5 V. Such surprising efficiencies obtained in our WOLEDs indicate that the reasonable application of interfacial exciplex should be a helpful way to develop high-performance and low cost WOLEDs with a simple technology.
关键词： high-performance,color stability,White organic light-emitting diodes,doping-free,interfacial exciplex
更新于2025-09-23 15:19:57