Cu substitution boosts self-trapped exciton emission in zinc-based metal halides for sky-blue light-emitting diodes. Issue 25 (30th May 2022)

• Record Type: Journal Article
• Authors: Ren, Miao; Zhang, Shuai; Chang, Tong; Yao, Jiandong; Gao, Yilin; Yuan, Mingjian; Cao, Sheng; Zhao, Jialong; Zou, Bingsuo; Zeng, Ruosheng
• Is Part Of: Journal of materials chemistry. Volume 10:Issue 25(2022)
• Page Start: 9530
• Page End: 9537
• Publication Date: 2022-05-30
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d2tc01637k
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : The PLQY of Cu:(PEA)2 ZnX4 metal halides was greatly boosted after Cu substitution and photophysical mechanisms are revealed. Further, Cu:(PEA)2 ZnX4 was used as the active layer and sky-blue light-emitting diodes were prepared for the first time. Abstract : Substantial progress has been made in light-emitting diodes (LEDs) based on red- and green-emitting lead halides. However, reducing the lead toxicity of emissive materials and achieving high-efficiency blue-emitting LED beads on lead-free metal halides remains a great challenge. Herein, lead-free zero-dimensional metal halides Cu:(PEA)2 ZnX4 (X = Cl, Br) were developed to solve the above bottlenecks. Cu substitution enhanced the photoluminescence quantum yield (PLQY) of (PEA)2 ZnBr4 from 3.4% to 55% and that of (PEA)2 ZnCl4 from 2.7% to 34.5%. Interestingly, dual emission peaks are observed at low temperatures due to the presence of two excitation structures on the potential energy surface of the triplet state excited states. The self-trapped excitons of Cu:(PEA)2 ZnBr4 can cross this potential barrier between the two triplet-state excited states by acquiring thermal energy, but Cu:(PEA)2 ZnCl4 cannot overcome the barrier due to the different molecular environments. For the first time, using Cu:(PEA)2 ZnX4 as the light-emitting layers, sky-blue LEDs with an external quantum efficiency (EQE) of 0.45% and 0.83% for Cu:(PEA)2 ZnCl4 and Cu:(PEA)2 ZnBr4 were obtained, demonstrating that broadband light-emitting lead-free metal halides have great potential for sky-blue light-emitting diode applications.