Abstract
Nonradiative recombination at perovskite/charge transport layer interfaces is caused by surface defects and instability, and it is known to limit the long-term development of perovskite solar cells (PSCs). To overcome this issue, the three-dimensional/two-dimensional (3D/2D) perovskite heterojunction has emerged as a possible solution to improve the stabilities and efficiency of PSCs. Herein, we employ a simple one-step method to prepare n-i-p-structured PSCs using a 3D/2D perovskite heterojunction as the absorption layer. For this purpose, the large and non-centrosymmetric 4,4-difluorocyclohexylammonium (DFCHA+) cation, which has been confirmed to be a valid organic spacer in 2D Ruddlesden–Popper (RP) phase perovskites, is employed as an organic ligand for post-treatment of the surfaces of MAPbI3 films. The presence of an ultrathin 2D RP phase perovskite was confirmed on the surface, and the 3D/2D perovskite heterojunction was successfully constructed. Benefitting from surface post-treatment, the density of the surface trap states was reduced with effective passivation. In addition, nonradiative recombination was suppressed, and the interface bands were aligned. As a result, the optimal device achieved a power conversion efficiency of 21.93% with a remarkable open-circuit voltage (VOC) of 1.14 V, a current density (JSC) of 23.71 mA cm−2, and a fill factor of 0.82. Furthermore, owing to the hydrophobicity of the DFCHA+ cation, the unencapsulated device was able to maintain an initial efficiency of 82.3% after storage for 500 h at a relative humidity of ∼45%. We believe that this post-treatment strategy has wide application potential in the field of photovoltaic devices.
Funder
National Natural Science Foundation of China
Ministry of Science and Technology of the People's Republic of China
China Postdoctoral Science Foundation
East China Normal University
Subject
General Engineering,General Materials Science