Enhancing the performance of Quasi-2D perovskite blue light emitting diodes via a WS2 energy matching layer

Due to the deep energy levels, the external quantum efficiency (EQE) of the blue perovskite light-emitting diode (PeLED) is far lower than its green, red, and near-infrared counterparts, which has exceeded 20%. The mismatched energy levels between perovskites and the hole transporting layer (HTL) still hinder the hole injection and consequent improvement of blue PeLED device performance. Here, a two-dimensional material, WS2 (Tungsten disulfide), was introduced to match the energy levels between perovskites and HTL and enhanced the hole injection. The WS2 HTL-based perovskite FAPbBr3-xClx blue LED achieved a luminance of 990 cd/m2 with an EQE of 3.24%, which surpasses the performance of previously reported for the formamidinium (FA) based system, indicating the potential of WS2 for PeLEDs.