CIE-tunable OLED Based on Hot Exciton Single Emitter
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.
color gamut adjustableorganic light-emitting diodeshot exciton materials
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