美国加州大学Xu, Sheng团队开发了具有高效载流子动力学的钙钛矿超晶格。相关研究成果于2022年8月10日发表在《自然》。
与它们的三维（3D）对应物相比，低维金属卤化物钙钛矿（2D和准2D；B2An1MnX3n+1, 例如B=R-NH3+, A=HC(NH2)2+, Cs+; M=Pb2+, Sn2+; X=Cl, Br, I）具有周期性无机-有机结构，已显示出良好的稳定性和无磁滞电性能。然而，由于多晶体中的晶界和随机取向量子阱，其独特的多量子阱结构限制了器件效率。在单晶中，通过厚度方向的载流子传输受到层状绝缘有机间隔层的阻碍。此外，有机间隔层的强量子限制限制了自由载流子的生成和传输。此外，已开发出无铅金属卤化物钙钛矿，但其器件性能受其低结晶度和结构不稳定性的限制。
该文报道了一种低维金属卤化物钙钛矿BA2MAn1SnnI3n+1（BA，丁基铵；MA，甲基铵；n=1,3,5）超晶格。无机板垂直于衬底排列，并以平行于衬底的纵横交错的2D网络互连，从而在三维中实现高效的载流子传输。晶格失配衬底压缩有机间隔层，这削弱了量子限制。在准稳态下验证了超晶格太阳能电池的性能，显示出稳定的12.36%光电转换效率。此外，带内激子弛豫过程可能产生异常高的开路电压（VOC）。
附：英文原文
Title: Perovskite superlattices with efficient carrier dynamics
Author: Lei, Yusheng, Li, Yuheng, Lu, Chengchangfeng, Yan, Qizhang, Wu, Yilei, Babbe, Finn, Gong, Huaxin, Zhang, Song, Zhou, Jiayun, Wang, Ruotao, Zhang, Ruiqi, Chen, Yimu, Tsai, Hsinhan, Gu, Yue, Hu, Hongjie, Lo, Yu-Hwa, Nie, Wanyi, Lee, Taeyoon, Luo, Jian, Yang, Kesong, Jang, Kyung-In, Xu, Sheng
Issue&Volume: 2022-08-10
Abstract: Compared with their three-dimensional (3D) counterparts, low-dimensional metal halide perovskites (2D and quasi-2D; B2An1MnX3n+1, such as B=R-NH3+, A=HC(NH2)2+, Cs+; M=Pb2+, Sn2+; X=Cl, Br, I) with periodic inorganic–organic structures have shown promising stability and hysteresis-free electrical performance1,2,3,4,5,6. However, their unique multiple-quantum-well structure limits the device efficiencies because of the grain boundaries and randomly oriented quantum wells in polycrystals7. In single crystals, the carrier transport through the thickness direction is hindered by the layered insulating organic spacers8. Furthermore, the strong quantum confinement from the organic spacers limits the generation and transport of free carriers9,10. Also, lead-free metal halide perovskites have been developed but their device performance is limited by their low crystallinity and structural instability11. Here we report a low-dimensional metal halide perovskite BA2MAn1SnnI3n+1 (BA, butylammonium; MA, methylammonium; n=1,3,5) superlattice by chemical epitaxy. The inorganic slabs are aligned vertical to the substrate and interconnected in a criss-cross 2D network parallel to the substrate, leading to efficient carrier transport in three dimensions. A lattice-mismatched substrate compresses the organic spacers, which weakens the quantum confinement. The performance of a superlattice solar cell has been certified under the quasi-steady state, showing a stable 12.36% photoelectric conversion efficiency. Moreover, an intraband exciton relaxation process may have yielded an unusually high open-circuit voltage (VOC).
DOI: 10.1038/s41586-022-04961-1
Source: https://www.nature.com/articles/s41586-022-04961-1