Suppressing defect states in CsPbBr3 perovskite via magnesium substitution for efficient all-inorganic light-emitting diodes

• Published in: Nanoscale horizons 2019-07, Vol.4 (4), p.924-932
• Main Authors: Huang, Qi, Zou, Yatao, Bourelle, Sean A, Zhai, Tianshu, Wu, Tian, Tan, Yeshu, Li, Yajuan, Li, Junnan, Duhm, Steffen, Song, Tao, Wang, Lu, Deschler, Felix, Sun, Baoquan
• Format: Article
• Language: English
• Subjects: Carrier density; Current efficiency; Electroluminescence; Free energy; Heat of formation; Laser applications; Lead compounds; Light emitting diodes; Magnesium; Metal halides; Morphology; Optoelectronics; Organic light emitting diodes; Perovskites; Photoelectrons; Photoluminescence; Spectrum analysis; Substitutes; Toxicity
• ISSN: 2055-6764; 2055-6764
• DOI: 10.1039/c9nh00066f

Lead-halide perovskites are promising materials for photovoltaic, light emitting and laser applications due to their excellent optoelectronic properties. Of note, light-emitting diodes (LEDs) based on these materials have attained efficiencies exceeding 20% with emission in either red or green colour. However, the toxicity of lead ions would raise potential risks to users and the environment. Herein, it is desirable to replace lead with sustainable and non-toxic elements. In this work, we show that the photoluminescence quantum yield (PLQY) and electroluminescence (EL) efficiencies in CsPbBr3 perovskite can be dramatically improved upon partial replacement of lead ions with magnesium ones. The perovskite films with magnesium incorporation display improved film morphology and better crystallinity. Simulation results indicate a higher defect formation energy upon incorporating magnesium. As a result, an enhanced PLQY and a longer photoluminescence lifetime are obtained in the magnesium incorporated halide perovskite film. Time-resolved spectroscopy and transient absorption are used to conduct a detailed analysis of the recombination pathways, and a reduction in non-radiative loss is observed, in conjunction with a significant decrease in the drop of carrier density in the first few picoseconds—from 60% to 10%—that is often associated with trap filling. In addition, ultraviolet photoelectron spectroscopy measurement indicates that the hole injection barrier is dramatically reduced with magnesium. Under optimized conditions, perovskite LEDs based on CsPb0.9Mg0.1Br3 achieved a high luminance of 25 450 cd m−2 and a current efficiency of 13.13 cd A−1, which is enhanced by approximately 100-fold compared to the device without substitution. Our results provide new approaches for more sustainable and efficient perovskite LEDs in the crucial green emission region.