Affiliation:
1. South China Academy of Advanced Optoelectronics South China Normal University Guangzhou 510006 China
2. Department of Electronic Engineering The Chinese University of Hong Kong Shatin New Territories 999077 Hong Kong
3. Department of Physics and William Mong Institute of Nano Science and Technology The Hong Kong University of Science and Technology Clear Water Bay Kowloon 999077 Hong Kong
4. Department of Applied Physics The Hong Kong Polytechnic University Kowloon 999077 Hong Kong
5. Department of Physics The Chinese University of Hong Kong Shatin New Territories 999077 Hong Kong
Abstract
AbstractThe inefficient charge transport and large exciton binding energy of quasi‐2D perovskites pose challenges to the emission efficiency and roll‐off issues for perovskite light‐emitting diodes (PeLEDs) despite excellent stability compared to 3D counterparts. Herein, alkyldiammonium cations with different molecular sizes, namely 1,4‐butanediamine (BDA), 1,6‐hexanediamine (HDA) and 1,8‐octanediamine (ODA), are employed into quasi‐2D perovskites, to simultaneously modulate the injection efficiency and recombination dynamics. The size increase of the bulky cation leads to increased excitonic recombination and also larger Auger recombination rate. Besides, the larger size assists the formation of randomly distributed 2D perovskite nanoplates, which results in less efficient injection and deteriorates the electroluminescent performance. Moderate exciton binding energy, suppressed 2D phases and balanced carrier injection of HDA‐based PeLEDs contribute to a peak external quantum efficiency of 21.9%, among the highest in quasi‐2D perovskite based near‐infrared devices. Besides, the HDA‐PeLED shows an ultralong operational half‐lifetime T50 up to 479 h at 20 mA cm‒2, and sustains the initial performance after a record‐level 30 000 cycles of ON–OFF switching, attributed to the suppressed migration of iodide anions into adjacent layers and the electrochemical reaction in HDA‐PeLEDs. This work provides a potential direction of cation design for efficient and stable quasi‐2D‐PeLEDs.
Funder
National Natural Science Foundation of China