色坐标可调的单发光体热激子OLED

CIE-tunable OLED Based on Hot Exciton Single Emitter

色域可调的高效有机发光二极管(OLED)器件由于可实现广泛的色彩表现范围,为显示、照明和光电应用带来了新的可能性。本工作以热激子材料C3为唯一发光客体,通过改变主体及客体浓度,制备了系列色坐标可调的OLED器件。在2.5%低掺杂浓度下,器件中C3分子的三个激发态都呈现较显著的发光,单主体与双主体器件L1、L3可分别实现暖白光与冷白光发射,在17 V工作电压下对应的CIE坐标分别为(0.298,0.381)、(0.241,0.329)。在较高掺杂浓度(10%)下,第二单重态的发射占主导地位,单主体与双主体器件L2和L4分别呈现黄绿光及绿光。其中,双主体器件由于具有更好的载流子平衡,相比单主体器件启动电压降低、器件效率提升且效率衰减减少。由于存在高能级反向系间窜越的热激子机制,器件L4的最大EQE为5.36%,突破了传统荧光EQE的理论上限(5%)。本工作为设计基于单发光组分的色域可调及白光OLED器件提供了新的思路。

High-efficiency organic light-emitting diodes(OLEDs)with adjustable gamut have brought new possibil⁃ities for display,lighting and optoelectronic applications due to their wide color range.In this work,a series of OLEDs featuring adjustable color coordinates have been fabricated simply by modulation of both host and guest con⁃centrations,using the hot exciton material C3 as the single luminescent emitter.At a low doping concentration of 2.5%,the C3 molecule in OLEDs exhibits multiple emissions from all its three excited states.Devices L1 and L3,respectively employing single-host and double-host configurations,achieve warm white and cold white light emissions correspondingly.Their CIE coordinates are(0.298,0.381)and(0.241,0.329),respectively,at an operating voltage of 17 V.At a higher doping concentration(10%),the emission from the second singlet state predominates,resulting in yellow-green and green emitting light in single-(L2)and double-host(L4)devices,respectively.Nota⁃bly,owing to better carrier balance,the dual-host device demonstrated a lower turn-on voltage,improved device effi⁃ciency,and reduced efficiency roll-off compared to its single-agent device.Due to the hot exciton mechanism which facilitates high-energy-level reverse intersystem crossing,device L4 presents a maximum EQE of 5.36%,surpassing the theoretical upper limit of traditional fluorescent EQE(5%).This work provides a new approach for designing col⁃or-tunable and white OLEDs based on a single fluorescent emitter.