2,6‐Dicarbonitrile Diphenyl‐1λ5‐Phosphinine (DCNP)—A Robust Conjugated Building Block for Multi‐Functional Dyes Exhibiting Tunable Amplified Spontaneous Emission

Abstract

AbstractHighly efficient organic light‐emitting diodes (OLEDs) with the concurrent achievement of high external electroluminescence quantum efficiency (EQE) and low light amplification thresholds under optical excitation have been considered as a crucial evolution towards the development of high‐performance electrically pumped organic semiconductor laser diodes. Herein, a series of 2,6‐dicarbonitrile‐diphenyl‐1λ5‐phosphinine (DCNP) based donor (D)‐acceptor (A) type dyes with different electron‐withdrawing and donating moieties have been designed and characterized. The well‐manipulated D‐A strength with tunable optical properties guaranteed the low amplified spontaneous emission (ASE) thresholds of below 10 µJ cm−2 and furnished a wide‐range color‐tuning capability in the visible region (485–595 nm). Furthermore, employing a thermally‐activated delayed fluorescence (TADF) molecule as a triplet harvester boosted the performance of OLEDs based on mDMCz that exhibits an exceptional EQE value of 18.4% which is an eightfold enhancement as compared with that of standard fluorescence OLEDs. Also, the TADF‐assistant fluorescence (TAF) system enables a reduction of the ASE threshold to 3 µJ cm−2 and excellent ASE stability. These results provide a rational design strategy to construct color‐tunable lasing dyes with reduced ASE thresholds and clarify their potentiality as the fluorescent dopant in the TAF system to utilize up‐converted triplet excitons via efficient energy transfer.