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Carrier Diffusion and Recombination Anisotropy in the MAPbI3 Single Crystal
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2021-06-18 , DOI: 10.1021/acsami.1c07056
Jie Zhang 1 , Kaiyu Wang 1 , Qing Yao 1 , Ye Yuan 1 , Jianxu Ding 1 , Weiwei Zhang 1 , Haiqing Sun 1 , Chenyu Shang 1 , Changqian Li 1 , Tianliang Zhou 2 , Shuping Pang 3
Affiliation  

MAPbI3, one of the archetypical metal halide perovskites, is an exciting semiconductor for a variety of optoelectronic applications. The photoexcited charge-carrier diffusion and recombination are important metrics in optoelectronic devices. Defects in grain interiors and boundaries of MAPbI3 films cause significant nonradiative recombination energy losses. Besides defect impact, carrier diffusion and recombination anisotropy introduced by structural and electronic discrepancies related to the crystal orientation are vital topics. Here, large-sized MAPbI3 single crystals (SCs) were grown, with the (110), (112), (100), and (001) crystal planes simultaneously exposed through the adjusting ratios of PbI2 to methylammonium iodide (MAI). Such MAPbI3 SCs exhibit a weak n-type semiconductor character, and the Fermi levels of these planes were slightly different, causing a homophylic p–n junction at crystal ledges. Utilizing MAPbI3 SCs, the photoexcited carrier diffusion and recombination within the crystal planes and around the crystal ledges were investigated through time-resolved fluorescence microscope. It is revealed that both the (110) and (001) planes were facilitated to be exposed with more MAI in the growth solutions, and the photoluminescence (PL) of these planes manifesting a red-shift, longer carrier lifetime, and diffusion length compared with the (100) and (112) planes. A longer carrier diffusion length promoted photorecycling. However, excessive MAI-assisted grown MAPbI3 SCs could increase the radiative recombination. In addition, it revealed that the carrier excited within the (001) and (112) planes was inclined to diffuse toward each other and was favorable to be extracted out of the grain boundaries or crystal ledges.

中文翻译:

MAPbI 3单晶中的载流子扩散和复合各向异性

MAPbI 3是一种典型的金属卤化物钙钛矿,是用于各种光电应用的令人兴奋的半导体。光激发电荷载流子扩散和复合是光电器件中的重要指标。MAPbI 3薄膜的晶粒内部和边界缺陷会导致显着的非辐射复合能量损失。除了缺陷影响之外,与晶体取向相关的结构和电子差异引入的载流子扩散和复合各向异性也是至关重要的主题。在这里,通过调节 PbI 2 的比例,生长了大尺寸的 MAPbI 3单晶(SCs),其中(110)、(112)、(100)和(001)晶面同时暴露甲基碘化铵 (MAI)。这种 MAPbI 3 SCs 表现出弱的 n 型半导体特性,这些平面的费米能级略有不同,导致晶体边缘处的同系 p-n 结。利用 MAPbI 3 SC,通过时间分辨荧光显微镜研究了晶面内和晶体边缘周围的光激发载流子扩散和复合。结果表明,(110) 和 (001) 平面都有助于在生长溶液中暴露更多的 MAI,并且与这些平面相比,这些平面的光致发光 (PL) 表现出红移、更长的载流子寿命和扩散长度与 (100) 和 (112) 平面。较长的载流子扩散长度促进光回收。然而,过多的 MAI 辅助生长的 MAPbI3 SCs 可以增加辐射复合。此外,还揭示了在(001)和(112)面内激发的载流子倾向于相互扩散,并且有利于从晶界或晶缘中提取出来。
更新日期:2021-06-30
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