A research team led by Prof. XIAO Zhengguo from the University of Science and Technology of China (USTC) has grown high-quality, large-area, ultra-thin perovskite single crystals (SCs) using space-confined inverse-temperature crystallization (SIC) method, creating a new type of highly bright and stable single-crystal perovskite LED (SC-PeLED). The work was published in Nature Photonics on February 27th.
(a) diagram of the SIC method. (b) micrograph of the SC. (c) structure of the PeLED device. (Image by CHEN Wenjing et al.)
Metal-halide perovskites have become a new generation of LED display and lighting material because of their narrow emission bandwidth, tunable emission wavelength, and bipolar conduction. However, the operational stability of most reported PeLED devices still lags behind those of the organic LEDs (OLEDs) and quantum-dot LEDs (QLEDs). The stability of PeLED devices is affected by various factors such as ion migration, carrier injection imbalance, and Joule heating.
To tackle the above issues, XIAO’s research team used the SIC method to directly grow in situ perovskite SCs with a composition of methylammonium-formamidinium lead bromide (MA0.8FA0.2PbBr3) on top of a hole-transport layer (HTL). By adjusting the growth conditions and introducing organic amines and polymers, high-quality SCs with a low trap density were obtained. Such SCs displayed a high internal photoluminescence quantum yield (PLQYint) of 90%.
The researchers then reduced the SC thickness to 1.5 µm, which further boosted the luminance to 86,000 cd m−2 and external quantum efficiency (EQE) of the SC-PeLEDs to 11.2%, respectively. Furthermore, benefiting from the suppressed ion migration in SCs, the lifetime of such PC-PeLEDs reached a value of 12,500 h. This new type of SC-PeLED has become one of the most stable PeLED devices and has earned the threshold of commercialization.
The above work demonstrates that using thin perovskite SCs as the light-emitting layer is a feasible solution to the stability problem and that PeLEDs have a great prospect in LED display and lighting.
(Written by SUI Bingcheng, edited by SHU Yukang, USTC News Center)