Band Edge Control of Quasi‐2D Metal Halide Perovskites for Blue Light‐Emitting Diodes with Enhanced Performance
Band Edge Control of Quasi‐2D Metal Halide Perovskites for Blue Light‐Emitting Diodes with Enhanced Performance
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DOI：
10.1002/adfm.202103299
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发表时间：
2021-08
影响因子：
19
通讯作者：
Michael Worku;Azza Ben‐Akacha;S. Sridhar;Jordan R. Frick;Shichen Yin;Qingquan He;Alex J. Robb;Maya Chaaban;He Liu;J. S. Raaj Vellore Winfred;Kenneth Hanson;F. So;D. Dougherty;Biwu Ma
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文献类型：
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作者：
Michael Worku;Azza Ben‐Akacha;S. Sridhar;Jordan R. Frick;Shichen Yin;Qingquan He;Alex J. Robb;Maya Chaaban;He Liu;J. S. Raaj Vellore Winfred;Kenneth Hanson;F. So;D. Dougherty;Biwu Ma
永久发光二极管（PeLED）因其作为下一代显示技术的潜力而受到极大关注。虽然在具有超过20%的外部量子效率（EQE）的绿色、红色和近红外PeLED中已经取得了显著的进展，但是获得高性能蓝色PeLED仍然是一个挑战。由于蓝色PeLED中的大电荷注入势垒而导致的不良电荷平衡已被确定为实现高效率的主要障碍之一。在这里，报告了具有增强的电荷平衡和器件性能的蓝色PeLED的钙钛矿发光层的带边控制。通过使用具有不同偶极矩的有机间隔基阳离子，即苯乙基铵（PEA）、甲氧基苯乙基铵（MePEA）和4-氟苯乙基铵（4FPEA），准2D钙钛矿的带边被调谐而不影响它们的带隙。详细的表征和计算研究证实，偶极矩修改的影响主要是静电作用，导致MePEA的电离能变化约为0.45 eV，4FPEA基薄膜的电离能变化约为-0.65eV。相对于PEA基薄膜。随着电荷平衡的改善，基于MePEA准2D钙钛矿的蓝色PeLED显示出与基于PEA的对照器件相比EQE的两倍增加。
Perovskite light‐emitting diodes (PeLEDs) have received great attention for their potential as next‐generation display technology. While remarkable progress has been achieved in green, red, and near‐infrared PeLEDs with external quantum efficiencies (EQEs) exceeding 20%, obtaining high performance blue PeLEDs remains a challenge. Poor charge balance due to large charge injection barriers in blue PeLEDs has been identified as one of the major roadblocks to achieve high efficiency. Here band edge control of perovskite emitting layers for blue PeLEDs with enhanced charge balance and device performance is reported. By using organic spacer cations with different dipole moments, that is, phenethyl ammonium (PEA), methoxy phenethyl ammonium (MePEA), and 4‐fluoro phenethyl ammonium (4FPEA), the band edges of quasi‐2D perovskites are tuned without affecting their band gaps. Detailed characterization and computational studies have confirmed the effect of dipole moment modification to be mostly electrostatic, resulting in changes in the ionization energies of ≈0.45 eV for MePEA and ≈ −0.65 eV for 4FPEA based thin films relative to PEA‐based thin films. With improved charge balance, blue PeLEDs based on MePEA quasi‐2D perovskites show twofold increase of the EQE as compared to the control PEA based devices.