Bromine Doping as an Efficient Strategy to Reduce the Interfacial Defects in Hybrid Two-Dimensional/Three-Dimensional Stacking Perovskite Solar Cells

Abstract

Solar-to-electricity conversion efficiency, power conversion efficiency (PCE), and stability are two important aspects of perovskite solar cells (PSCs). However, both aspects are difficult to simultaneously enhance. In the recent two years, two-dimensional (2D)/three-dimensional (3D) stacking structure, designed by covering the 3D perovskite with a thin 2D perovskite capping layer, was reported to be a promising method to achieve both a higher PCE and improved stability simultaneously. However, when reducing the surface defects of 3D perovskite, the thin 2D capping layer itself may probably introduce additional interfacial defects in a 2D/3D stacking structure, which is thought to be able to trigger trap-assisted nonradiative recombination or ion migration. Thus, efforts should be paid to reduce the interfacial defects of 2D hybrid perovskite when serving as a modification layer in a 2D/3D stacking structure PSCs. Here, we demonstrate that bromine (Br) doping of the 2D perovskite capping layer is an efficient strategy to passivate interfacial defects robustly, by which the photoluminescence lifetime is enhanced notably, whereas the interfacial charge recombination is suppressed a lot. As a result, the PCE is enhanced from 18.01% (3D perovskite) to 20.07% (Br-doped 2D/3D perovskite) along with improved moisture stability.

Synergetic surface charge transfer doping and passivation toward high efficient and stable perovskite solar cells

“…For the perovskite film with FDC-2-5Cl treatment, the peaks located at 283.67 eV and 285.57 eV are also corresponding to the C-C peak and C-N peak, respectively. Noticeably, the C=O peak at 287.17 eV is significantly suppressed in perovskite film with FDC-2-5Cl treatment, and the formation of C=O bond is related to the reaction between the organic cations in perovskite and absorbed oxygen and moisture when exposing to ambient air ( Chen et al., 2018 ; Lv et al., 2018 ; Sun et al., 2017 ). This result indicates that the FDC-2-5Cl treatment could enhance the tolerance of perovskite film to oxygen and moisture.…”

Attaining High Photovoltaic Efficiency and Stability with Multidimensional Perovskites

“…The cationic ammonium ends and the anion counterions in the 2DP layer passivate the dangling bonds, thereby boosting photovoltage and reducing hysteresis. At the same time, care must be taken to ensure the 2DP layer itself does not cause additional interfacial defects, for example, by bromine doping of the 2DP …”

How machine learning can help select capping layers to suppress perovskite degradation

“…The choice of organic halides is known to affect device stability, however the relationship between structure and stability has not been fully explored, in part because the parameter space is vast 8 . Perovskite thin-film deposition with a range of organic halides has been reported, including benzene rings/phenyl with amine (e.g., phenylethylammonium iodide 9 – 11 , phenylethylammonium bromide 9 , 12 , aniline iodide 13 , 14 , benzylammonium iodide 14 , teophylline 15 , caffeine 16 ), long carbon chains with amine (e.g ., n -butylammonium iodide 17 , 18 , n- octylammonium iodide 18 ), fluorous amine (e.g., 2‐(4‐fluorophenyl)ethylammonium iodide 19 ), branched amines (e.g., 1,8-octanediammonium iodide 20 , diethylammonium bromide 21 , diethylammonium iodide 21 , n -hexyl trimethyl ammonium bromide 6 ), and large, complex structures (e.g., Eu-porphyrin complex 22 ). Photovoltaic devices based on these materials demonstrated improved stability and efficiency than their non-capped controls under various environmental test conditions.…”