The Spacer Cations Interplay for Efficient and Stable Layered 2D Perovskite Solar Cells

Abstract

Organic spacer cations in layered 2D (A1)2(A2)n−1BnX3n+1 (where A1 is an organic cation acting as a spacer between the perovskite layers, A2 is a monovalent cation, e.g., Cs+,CH3NH3+, CH(NH2)2+) perovskite materials improve the long‐term stability of the resulting solar cells, but hamper their power conversion efficiency due to poor carrier generation/transportation. Rational guidelines are thus required to enable the design of organic spacer cations. Herein, mixed A1 cations are employed in layered 2D perovskites to investigate the interplay between alkylamine cations and unsaturated alkylamine cations. It is revealed that alkylamine spacer cations are able to facilitate precursor assembly, which results in the orientated growth of perovskite crystals. Unsaturated alkylamine cations further lead to reduced exciton binding energy, which improves carrier pathway in the 2D perovskites. By mixing both cations, substantially improved open circuit voltage is observed in the resultant photovoltaic cells with the efficiency of 15.46%, one of the highest one based on (A1)2(A2)3Pb4I13 layered 2D perovskites. The generality of the design principle is further extended to other cation combinations.

Proton-transfer-induced 3D/2D hybrid perovskites suppress ion migration and reduce luminance overshoot

“…phenethylammonium halide (PEAX), or n-butylammonium halide (n-BAX)) and the salts of a 3D perovskite (e.g. methylammonium halide (MAX) and lead halide (PbX 2 )) have been dissolved together in a solvent or a mixed solvent 8,[14][15][16][17][18][19] . Here, unlike the conventional way, we incorporate a liquid-form neutral reagent, benzylamine (BnA) into the methylammonium lead bromide (MAPbBr 3 ) precursor to form 3D/2D hybrid perovskites 20 .…”

High‐Quality Ruddlesden–Popper Perovskite Film Formation for High‐Performance Perovskite Solar Cells

“…[ 96 ] In comparison with the unsaturated aromatic alkylamine cations, the chain alkylamine cations are more likely to manage the precursor assembly and promote the vertical growth orientation of RP perovskite crystals. [ 97 ] With regard to the chain of space alkylamine cations, it has been reported that space cations with shorter chain favored the high‐quality crystallization of RP perovskites. [ 76 ] Huang's group has attributed this advantage of shorter‐chain‐based space cations to the reduced steric hindrance of the perovskite during self‐assembly.…”

“…Figure a–d displays the RP perovskite film formation process based on GA + and PEA + as a second space cation. [ 97,99 ] The interaction between space cations and solvents controls the evaporation rate of solvents and further influences the supersaturation and crystallization dynamics during the RP perovskite film formation process, which plays a crucial role in the crystal growth orientation. [ 68 ] All these hint that the high‐quality RP perovskite film can be achieved via appropriately tuning organic space cations, which will be discussed later in detail.…”

Mechanisms and Suppression of Photoinduced Degradation in Perovskite Solar Cells

“…[157] This study highlights the importance of the stability of precursor solution, especially under illumination. Besides, partial substitution of MA + by other larger cations, such as GA + (CH 6 N 3 + ), [158] AVA + (HOOC(CH 2 ) 4 NH 3 + ), [44] BA + (C 4 H 9 NH 3 + ), [159] PEA + (C 6 H 5 (CH 2 ) 2 NH 3 + ), [160] has also proved to be an effective way to improve the stability of perovskites. [77] Although mixed cations can improve the photostability of perovskite, the organic cations may still be potentially deprotonated under intense light illumination.…”