Materials and Process Simulation Center and ‡The Resnick Sustainability Institute, California Institute of Technology , Pasadena, California 91125, United States.
Nano Lett. 2016 May 11;16(5):3335-40. doi: 10.1021/acs.nanolett.6b00964. Epub 2016 Apr 25.
Two-dimensional (2D) halide perovskites are emerging as promising candidates for nanoelectronics and optoelectronics. To realize their full potential, it is important to understand the role of those defects that can strongly impact material properties. In contrast to other popular 2D semiconductors (e.g., transition metal dichalcogenides MX2) for which defects typically induce harmful traps, we show that the electronic activities of defects in 2D perovskites are significantly tunable. For example, even with a fixed lattice orientation one can change the synthesis conditions to convert a line defect (edge or grain boundary) from electron acceptor to inactive site without deep gap states. We show that this difference originates from the enhanced ionic bonding in these perovskites compared with MX2. The donors tend to have high formation energies and the harmful defects are difficult to form at a low halide chemical potential. Thus, we unveil unique properties of defects in 2D perovskites and suggest practical routes to improve them.
二维（2D）卤化物钙钛矿作为纳米电子学和光电子学的有前途的候选材料而崭露头角。为了充分发挥其潜力，了解那些可能强烈影响材料性能的缺陷的作用非常重要。与其他常见的二维半导体（例如过渡金属二卤化物 MX2）不同，这些半导体中的缺陷通常会产生有害的陷阱，我们表明，2D 钙钛矿中缺陷的电子活性可显著调节。例如，即使晶格取向固定，也可以通过改变合成条件，将线缺陷（边缘或晶界）从电子受体转换为非活性位点，而不会产生深能隙状态。我们表明，这种差异源于与 MX2 相比，这些钙钛矿中增强的离子键合。供体倾向于具有高形成能，并且在卤化物化学势较低的情况下难以形成有害缺陷。因此，我们揭示了 2D 钙钛矿中缺陷的独特性质，并提出了改善这些性质的实用途径。
