Strategies for improving luminescence efficiencies of blue-emitting metal halide perovskites
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REVIEW ARTICLE
Strategies for improving luminescence efficiencies of blue‑emitting metal halide perovskites G. Krishnamurthy Grandhi1 · Ha Jun Kim1 · N. S. M. Viswanath2 · Han Bin Cho1 · Joo Hyeong Han1 · Seong Min Kim1 · Won Bin Im1 Received: 17 September 2020 / Revised: 9 November 2020 / Accepted: 11 November 2020 © The Korean Ceramic Society 2020
Abstract Lead halide perovskites (LHPs) are suitable as the emissive layers in light-emitting diodes (LEDs). The external quantum efficiency of green LEDs based on LHPs is now over 20%. Nevertheless, the blue LHP LEDs lag behind the green ones in terms of efficiency. Photoluminescence (PL) quantum yield (QY) and stability of the NCs under various operating conditions are two major factors that influence the LED performance. Therefore, to promote the efforts towards achieving improved LED efficiencies, herein, we summarize several synthetic methods that produce blue-emitting LHP NC, followed by several approaches devised to boost their PL QYs up to near unity. Light-induced anion segregation is one of the limitations of using blue-emitting mixed-halide LHPs, which triggers the attention to single halide, quantum-confined LHP nanoplatelets (NPLs). Syntheses, structure, and luminescent properties of organic–inorganic and all-inorganic blue-emitting LHP NPLs are discussed elaborately. In the last portion, the luminescent properties of lead-free metal halides, which are of current interest, are discussed, followed by an outlook and future directions. In conclusion, our review discusses various literature attempts to obtain stable blue-emitting LHP NCs, which can be helpful in a better design of the blue-emitting LHP NCs towards various light-emitting applications. Keywords Lead halide perovskites · Blue emission · Nanoplatelets · Lead-free perovskites
1 Introduction Lead halide perovskites (LHPs) have not only become an exciting class of materials for thin-film-based photovoltaics and light-emitting diodes (LEDs), but also have made their mark in the field of colloidal semiconductor nanocrystals (NCs). LHPs were discovered towards the end of the nineteenth century; however, their potential was fully realized only by the end of the twentieth century. Research on LHPs has gained immense interest over the past few years owing to their unique characteristics such as long charge-carrier diffusion lengths and high absorption cross-sections. LHPs have * Won Bin Im [email protected] 1
Division of Materials Science and Engineering, Hanyang University, 222 Wangsimni‑ro, Seongdong‑gu, Seoul 04763, Republic of Korea
School of Materials Science and Engineering, Chonnam National University, 77 Yongbong‑ro, Buk‑gu, Gwangju 61186, Republic of Korea
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found applications in lasers [1], gamma- and X-ray detection [2, 3], and photodetectors [4]. The efficiency of LHPbased solar cells has surpassed 20% over just a few years. LHPs display good electroluminescence (EL) properties, and their external quantum efficiency (EQE) has crossed 20% according to recent reports. Nano-size
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