Moon Jiyoung, Kwon Sunah, Alahbakhshi Masoud, Lee Yeonghun, Cho Kyeongjae, Zakhidov Anvar, Kim Moon J, Gu Qing
Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States.
Department of Electrical and Computer Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States.
ACS Appl Mater Interfaces. 2021 Feb 3;13(4):5368-5378. doi: 10.1021/acsami.0c17655. Epub 2021 Jan 21.
Hybrid organic-inorganic lead halide perovskites have attracted much attention in the field of optoelectronic devices because of their desirable properties such as high crystallinity, smooth morphology, and well-oriented grains. Recently, it was shown that thermal nanoimprint lithography (NIL) is an effective method not only to directly pattern but also to improve the morphology, crystallinity, and crystallographic orientations of annealed perovskite films. However, the underlining mechanisms behind the positive effects of NIL on perovskite material properties have not been understood. In this work, we study the kinetics of perovskite grain growth with surface energy calculations by first-principles density functional theory (DFT) and reveal that the surface energy-driven preferential grain growth during NIL, which involves multiplex processes of restricted grain growth in the surface-normal direction, abnormal grain growth, crystallographic reorientation, and grain boundary migration, is the enabler of the material quality enhancement. Moreover, we develop an optimized NIL process and prove its effectiveness by employing it in a perovskite light-emitting electrochemical cell (PeLEC) architecture, in which we observe a fourfold enhancement of maximum current efficiency and twofold enhancement of luminance compared to a PeLEC without NIL, reaching a maximum current efficiency of 0.07598 cd/A at 3.5 V and luminance of 1084 cd/m at 4 V.
有机-无机杂化铅卤化物钙钛矿因其具有高结晶度、光滑形态和取向良好的晶粒等理想特性，在光电器件领域备受关注。最近研究表明，热纳米压印光刻（NIL）不仅是一种直接构图的有效方法，而且还能改善退火钙钛矿薄膜的形态、结晶度和晶体取向。然而，NIL对钙钛矿材料性能产生积极影响背后的潜在机制尚未明确。在这项工作中，我们通过第一性原理密度泛函理论（DFT）进行表面能计算来研究钙钛矿晶粒生长动力学，并揭示在NIL过程中表面能驱动的优先晶粒生长是材料质量提升的关键因素，这一过程涉及表面法线方向受限晶粒生长、异常晶粒生长、晶体取向重排和晶界迁移等多重过程。此外，我们开发了一种优化的NIL工艺，并通过将其应用于钙钛矿发光电化学电池（PeLEC）结构中证明了其有效性。在该结构中，与未采用NIL的PeLEC相比，我们观察到最大电流效率提高了四倍，亮度提高了两倍，在3.5 V时达到最大电流效率0.07598 cd/A，在4 V时亮度达到1084 cd/m²。
