Small Science:多元有机配体增强钙钛矿量子阱层间电荷传输

WILEY开放获取（OA）旗舰期刊Small Science近日发表了来自普渡大学Letian Dou课题组的研究工作，他们开发了一种新型的杂化配体模式，进一步增强了钙钛矿量子阱层间电荷传输效率，探索了该材料在未来光电器件中的应用潜力。请同时关注文后彩蛋SMSC对话窦教授，了解一下他对钙钛矿材料光电应用的研究进展和未来兴趣。

钙钛矿太阳能电池近年来发展势头迅猛，能量转化效率已突破了25%。但是大规模制造铅基钙钛矿太阳能电池依然受制于铅的毒性以及其材料自身的稳定性。作为一种环境友好的钙钛矿材料，锡基钙钛矿具有极大的发展前景，但其稳定性问题依然有待解决。近年来二维钙钛矿材料也越来越受到重视，尤其是它的极高的稳定性有助于克服三维钙钛矿的稳定性问题。但是作为一种光电器件材料，二维钙钛矿材料中包含了大量的有机配体，严重阻碍了有效的电荷传输。

普渡大学的Letian Dou教授团队在2019年报道了一种新型二维钙钛矿材料，其中他们采用了一系列的有机共轭分子去取代传统的有机配体，实现了有机无机半导体的杂化，并且拓宽了对二维钙钛矿材料的光学及电子特性的调控，也极大地提高了二维钙钛矿的疏水稳定性（Nat. Chem. 2019，11, 1151–1157 ）。紧接着在2020年，该团队在此研究的基础上实现了二维卤素钙钛矿材料的横向异质结生长（Nature 2020，580, 614–620 ）。通过有机共轭配体的引入，显著地抑制了阴离子的扩散，从而得到了高稳定性、性能可调控的横向异质结。

基于以上的基础研究，该团队将这种高稳定性的有机无机杂化二维钙钛矿用于场效应晶体管（FET），发现该材料对于FET的稳定性及层内电荷传输都有所提高（J. Am. Chem. Soc. 2019, 39, 15577–15585）。近日，他们又开发了一种新型的杂化配体模式，进一步提升了层间电荷传输效率，探索了该材料在未来光电器件中应用的潜力（Small Science 2021）。长链共轭分子拥有较小的带隙，可以降低电荷传输的能垒，但是增大的无机层距离增加了电荷传输的距离。通过在长链共轭分子中掺杂入短链共轭分子，形成共轭有机配体混合物，可以使得二维钙钛矿层间配体形成如拉链般的穿插齿扣结构，减弱能垒的同时也有效地缩短了无机层之间的距离，同时增强了有机配体之间的作用力，从而加强了共轭有机分子的半导体性质在钙钛矿层间电荷传输中起的作用。这样的穿插配体结构通过提高电荷迁移率，延长电荷寿命，以及减弱空间电荷效应，进而使得层间电荷传输得到了进一步提升。电荷传输效率的提升进一步表现在了纯二维钙钛矿光伏器件的光电转换效率的提升上，尤其是光电流的提升。并且由该共轭有机分子制造的锡基二维钙钛矿光伏器件拥有极高的热稳定性及疏水稳定性。此发现为解决二维钙钛矿层间电荷传输的问题提供了新思路，有助于将来二维钙钛矿在光电器件中的进一步应用。

本文在线发表在Small Science 上（DOI：10.1002/smsc.202000024）。

作者介绍

Dr. Letian Dou is currently the Charles Davidson Chair Assistant Professor of Chemical Engineering at Purdue University. He obtained his B.S. in Chemistry from Peking University in 2009. He then joined Prof. Yang Yang’s group in the Department of Materials Science and Engineering at UCLA, and obtained his Ph.D. in 2014 (co-advised by Prof. Fred Wudl @UCSB in 2013). His doctoral research focused on the design and synthesis of conjugated polymers for organic photovoltaic applications. From 2014 to 2017, he was a Postdoc Fellow working with Prof. Peidong Yang at the Department of Chemistry, University of California-Berkeley and Materials Science Division, Lawrence Berkeley National Laboratory. His research interest includes the synthesis of organic semiconductors, inorganic nano structures, hybrid materials, and related optoelectronic properties and devices. He has published over 40 papers with more than 17000 citations.

SMSC: What got you interested in science in the first place? What is the most attractive thing as a scientist?

Dou: My passion in science originated from curiosity. I enjoy very much in discovery new knowledge in chemistry and physics. I also enjoy in solving practical problems using fundamental knowledges.

SMSC: Who have influenced your career and thinking the most?

Dou: My PhD advisor Prof. Yang Yang @ UCLA and postdoc advisor Prof. Peidong Yang @ UC Berkeley influenced me tremendously. They are both giants in academia and they taught me everything and turn me from a student into a scientist and a professor. In addition, I also leant a lot from Prof. Fred Wudl @ UCSB during my visit to his lab and Prof. Xinhua Wan during my undergrad study at Peking University. I’m very grateful to my advisors and mentors.

SMSC: How do you see the current and future trends in Halide Perovskites for Photonics and Optoelectronics?

Dou: This is an exciting area of research. Halide perovskite materials have amazing optical and electronic properties. Current research mainly focuses on fundamentals, but I hope many new technology breakthroughs will happen in the next few years and these materials will enable new devices (such as solar cell, lasers, LED, X-ray detectors) in commercial products. I think stability is one of the key issues now and materials chemistry will play a very important role here.

SMSC: What kind of impact would you expect from your research on 2D perovskite heterostructures?

Dou: Our work on perovskite heterostructure research 1) provides new fundamental understanding on the ion migration issue in halide perovskites, which may lead to better solutions to the stability problem; 2) opens up a new avenue towards integrated perovskite nanophotonics and nanoelectronics.

SMSC: What do you think is the most important characteristic for a researcher? Could you give some advice for young researchers starting out in your field?

Dou: I think I might be too young to answer this question. I think the most important characteristics are passion, curiosity, attitude, and perseverance. I encourage students and young researchers to be brave enough to think differently and take risks in doing research.