High-Efficiency TADF Materials Featuring Carbazole-Modified Spiroacridan-Pyrimidine Skeletons with an External Quantum Efficiency Exceeding 26% in Blue-Green Light Emission

Abstract

We report the design and synthesis of a novel sky-blue TADF emitter, 4SpAc35CzPy, incorporating spiroacridan as the donor and pyrimidine as the acceptor. Compared to the previously reported 4Ac35CzPy emitter, incorporating the fluorenyl controlled the twisting angle of the spiroacridan structure, enhancing the ICT (intramolecular charge transfer) effect and improving TADF performance. The electroluminescent device with a light emitting layer of 3% 4SpAc35CzPy doping concentration in o-DiCbzBz falls within the sky-blue light range, exhibiting emission λmax of 480 nm at 8 V with the CIE (0.163,0.275) and the brightness of 1230 cd/m2. An external quantum efficiency (ηEQE) of 20.2%, a current efficiency (ηCE) of 36.9 cd/A, a power efficiency (ηPE) of 33.2 lm/W were achieved. Adjusting the doping concentration leads to an even more efficient device with ηEQE of 26.7%, ηCE of 55.7 cd/A, and ηPE of 50.1 lm/W, outperforming similar acridan-based compounds.