In Situ Growth of 2D Perovskite Capping Layer for Stable and Efficient Perovskite Solar Cells

Abstract

Two-dimensional (2D) halide perovskites have recently been recognized as a promising avenue in perovskite solar cells (PSCs) in terms of encouraging stability and defect passivation effect. However, the efficiency (less than 15%) of ultra-stable 2D Ruddlesden-Popper PSCs still lag far behind their traditional three-dimensional (3D) perovskite counterparts. Here, we report a rationally designed 2D-3D perovskite stacking-layered architecture by in-situ growing 2D PEA 2 PbI 4 capping layers on top of 3D perovskite film, which drastically improved the stability of PSCs without compromising their high performance. Such 2D perovskite capping layer induces larger Fermi-level splitting in the 2D-3D perovskite film under light illumination, resulting in an enhanced open-circuit voltage (V oc ) and thus a higher efficiency of 18.51% in the 2D-3D PSCs. The time-resolved photoluminescence (TRPL) decay measurements indicate the facilitated hole-extraction in the This article is protected by copyright. All rights reserved. 22D-3D stacking-layered perovskite films, which is ascribed to the optimized energy band alignment and reduced non-radiative recombination at the sub gap states. Benefiting from the high moisture resistivity as well as suppressed ion migration of the 2D perovskite, the 2D-3D PSCs show significantly improved long-term stability, retaining nearly 90% of the initial PCE after 1000 h exposure in the ambient conditions with a high relative humidity level of 60±10%.

High‐Performance Perovskite Solar Cells with Enhanced Environmental Stability Based on a (p‐FC6H4C2H4NH3)2[PbI4] Capping Layer

“…[18,25,28,29] In our case, the extra fluorine atoms on the phenyl groups should enhance moisture tolerance further as already being proved in the recent report on the change of XRD patterns over time. The modified surface of 3D perovskite features a 2D perovskite capping layer, on top of which the FPEA + ion is presented at the terminal of the crystal with the hydrophobic p-fluorophenyl groups acting as the barrier to prevent the invasion of H 2 O from ambiance to grain boundaries in high humidity environments.…”

“…The pristine 3D perovskite film in Figure S8a (Supporting Information) showed densely packed pinhole-free perovskite layer with average domain size ≈350 nm. Furthermore, the ultrathin 2D perovskite capping layer can remedy the defects on the surface of the perovskite layer, so as to suppress nonradiative recombination loss [28] (vide infra). The newly formed 2D perovskite layer heals grain boundaries and functions as a self-encapsulating layer to block the moisture invasion ( Figure S8b-d, Supporting Information).…”

“…[24] In a similar report, a 3D-2D (MAPbI 3 -PEA 2 PbI 4 ) graded perovskite film resulted in an overall PCE of 19.89%. [26][27][28][29] Very recently, Lee et al incorporation of PEA 2 PbI 4 into the precursor solution of FAPbI 3 . [26][27][28][29] Very recently, Lee et al incorporation of PEA 2 PbI 4 into the precursor solution of FAPbI 3 .…”

Efficient and Stable FASnI3 Perovskite Solar Cells with Effective Interface Modulation by Low‐Dimensional Perovskite Layer

“…Aseries of charac-terizationsp roved that this modificationc ould improve the crystallinity of the FASnI 3 perovskite by incorporating Br and forming an ultrathin,l ow-dimensional perovskite layer at the interface, which led to the effective suppression of Sn 2 + oxidation, improved band level alignment,a nd decreased defect density.T hese effects contributed to the clear enhancement of conversion efficiency.M oreover,t his treatment also led to remarkably enhanced device stability, with approximately 80 % of the initial efficiency retained after 350 hl ight soaking, whereas the control devicefailed within 140 h. This work deepens our understanding of the suppression effect of PEABr on the oxidation of Sn 2 + and paves an ew way to fabricate promising tin halide PSCs by facile interface engineering. [48] Lee et al reported the growth of ultrathin 2D PEA 2 PbI 4 perovskite layers at the interface between the perovskite and carbon electrodes by spin-coating PEAI,r esulting in an improved perovskite/carbon contact, favorable energy levels alignment, enhanced conversion efficiency with negligible hysteresis, and better ambient stability. [46][47][48][49] By use of PEAI, Cho et al designedalow-dimensional perovskite layer on top of ab ulk 3D lead halide perovskite film with ap romisingc onversion efficiency of 20.1 %o n average with superior stability.…”

Progress of Lead‐Free Halide Double Perovskites

“…For example, the PCEs reported for Sn-based perovskite solar cells are usually less than 10%. [44][45][46][47][48] Recently, a stabilized PCE of 21.7% resulting from a 2D/3D bilayer PSC was reported. [41] High throughput calculations also demonstrate that these substitutions are likely to compromise the ideal optoelectronic properties of MAPbI 3 .…”