posted on 2019-09-10, 19:45authored byTianqi Niu, Jing Lu, Xuguang Jia, Zhuo Xu, Ming-Chun Tang, Dounya Barrit, Ningyi Yuan, Jianning Ding, Xu Zhang, Yuanyuan Fan, Tao Luo, Yalan Zhang, Detlef-M. Smilgies, Zhike Liu, Aram Amassian, Shengye Jin, Kui Zhao, Shengzhong Liu
Perovskite
solar cells based on two-dimensional/three-dimensional
(2D/3D) hierarchical structure have attracted significant attention
in recent years due to their promising photovoltaic performance and
stability. However, obtaining a detailed understanding of interfacial
mechanism at the 2D/3D heterojunction, for example, the ligand-chemistry-dependent
nature of the 2D/3D heterojunction and its influence on charge collection
and the final photovoltaic outcome, is not yet fully developed. Here
we demonstrate the underlying 3D phase templates growth of quantum
wells (QWs) within a 2D capping layer, which is further influenced
by the fluorination of spacers and compositional engineering in terms
of thickness distribution and orientation. Better QW alignment and
faster dynamics of charge transfer at the 2D/3D heterojunction result
in higher charge mobility and lower charge recombination loss, largely
explaining the significant improvements in charge collection and open-circuit
voltage (VOC) in complete solar cells.
As a result, 2D/3D solar cells with a power-conversion efficiency
of 21.15% were achieved, significantly higher than the 3D counterpart
(19.02%). This work provides key missing information on how interfacial
engineering influences the desirable electronic properties of the
2D/3D hierarchical films and device performance via ligand chemistry
and compositional engineering in the QW layer.