Lin, Yu KuanYu KuanLinChen, Chiung HanChiung HanChenWang, Yen YuYen YuWangYu, Ming HsuanMing HsuanYuYang, Jing WeiJing WeiYangNi, I. ChihI. ChihNiLin, Bi HsuanBi HsuanLinZhidkov, Ivan S.Ivan S.ZhidkovKurmaev, Ernst Z.Ernst Z.KurmaevLu, Yu JungYu JungLuCHU-CHEN CHUEH2023-07-242023-07-242023-01-012198-3844https://scholars.lib.ntu.edu.tw/handle/123456789/634118Quasi-2D perovskites have recently flourished in the field of luminescence due to the quantum-confinement effect and the efficient energy transfer between different n phases resulting in exceptional optical properties. However, owing to the lower conductivity and poor charge injection, quasi-2D perovskite light-emitting diodes (PeLEDs) typically suffer from low brightness and high-efficiency roll-off at high current densities compared to 3D perovskite-based PeLEDs, which is undoubtedly one of the most critical issues in this field. In this work, quasi-2D PeLEDs with high brightness, reduced trap density, and low-efficiency roll-off are successfully demonstrated by introducing a thin layer of conductive phosphine oxide at the perovskite/electron transport layer interface. The results surprisingly show that this additional layer does not improve the energy transfer between multiple quasi-2D phases in the perovskite film, but purely improves the electronic properties of the perovskite interface. On the one hand, it passivates the surface defects of the perovskite film; on the other hand, it promotes electron injection and prevents hole leakage across this interface. As a result, the modified quasi-2D pure Cs-based device shows a maximum brightness of > 70,000 cd m−2 (twice that of the control device), a maximum external quantum efficiency (EQE) of > 10% and a much lower efficiency roll-off at high bias voltages.enefficiency roll-off | hole blocking | interface engineering | Light-emitting diodes | quasi-2D perovskites[SDGs]SDG7journal article10.1002/advs.202302232374003662-s2.0-85163862794https://api.elsevier.com/content/abstract/scopus_id/85163862794