Ion Migration Inhibition And Two-step Printing Modification Of Halide Perovskite Film

The advantages of high performance and low cost of perovskite solar cells make them the hottest new photovoltaic technology in academic and industry research around the world.Its power conversion efficiency has increased from 3.8%to 25.8%in just over a decade,which is comparable to that of commercial silicon-based solar cells.However,the operational longevity and large-scale manufacture of perovskite photovoltaic devices are still the bottlenecks for its further commercialization.The migration and accumulation of charged ions in perovskite layer is an important factor leading to the degradation of device properties.Moreover,the complexity of crystallization control and environmental sensitivity limit the industrialization of photovoltaic technology.In view of the above problems,we aim to improve the stability and printability of perovskite layer.Focusing on the internal ion migration inhibition and two-step printing preparation modification of perovskite thin film,we optimize the photoelectric characteristics and long-term stability of devices,through ion anchoring design and environmental printing stability exploration,and realize efficient and stable environmental printing preparation of perovskite solar cells.The main research work is as follows:1)Ion anchoring in perovskite solar cells is particularly important in the pursuit of long-term stability.an"ionic polymer network"is constructed in perovskite films by introducing multifunctional poly(ionic-liquid)s additives,which can simultaneously form physical barriers and chemical bonds for anchoring ions and passivating defects.Meanwhile,the efficacy of imidazole-and quaternary ammonium-based poly(ionic-liquid)s on eliminating charged ions/defects migration and degradation in perovskite was compared from the perspective of defect passivation efficiency and ion migration activation energy.Finally,the perovskite device modified with quaternary ammonium-based poly(ionic-liquid)s achieves the highest power conversion efficiency of 22.22%and maintains the dark current-voltage characterization during the temperature cycle of-40℃-85℃.The corresponding unencapsulated devices can still maintain 80%of its initial efficiency under AM 1.5G illumination for nearly 1500 hours,and also show significantly improved stability under 85℃ thermal stress and high humidity environment.This diversified ion anchoring strategy provides an effective way to further improve the photoelectric performance and stability of perovskite solar cells.2)Grain boundary acts as the main channel of ion migration,which accelerates the degradation rate of perovskite films and devices.By introducing ammonium salt polymer(polyvinylbenzylamine hydroiodate)into the lead iodide film,low-dimensional crystal seeds containing polymer chains are formed to regulate film formation and fill grain boundaries of perovskite films.The ammonium salt polymer can interact with the edges of multiple perovskite grains to construct a multi-grain-boundary low-dimensional interconnection structure.The multiple effects of ammonium salt polymer compared with the monomer 4-vinylbenzylamine hydroiodate on perovskite nucleation crystallization and defect passivation are analyzed.Meanwhile,the promotion effect of the ammonium salt polymer on crystallization orientation,distribution state of lead iodide and charge carriers transport in perovskite film is further verified.The key point is that the construction of this low-dimensional interbody effectively inhibits the migration of internal ions,so that the photoelectric properties and stability of perovskite films can be improve simultaneously.Finally,the optimized perovskite solar cells achieve a champion power conversion efficiency of 23.30%.The corresponding unencapsulated device retains 88%(or 80%)of its initial efficiency after aging in air(or 85℃)for approximately 2500(or 800)hours,respectively.The multi-grain-boundary low-dimensional interconnect strategy demonstrated in this study provides a new idea for the study of ion migration inhibition in perovskite solar cells.3)The device performance based on scalable fabricating is lagging far behind the conventional lab-scale spin-coating in inert atmosphere.Here,an ionomer-templated lead iodide combined with cationic solvent engineering is develope to assist sequential blade-coating for fabricating high-quality perovskite films in ambient air.The stability and environmental printability of poly(quaternary ammonium salt)ionomer-based lead iodide ink is studied.Taking advantage of its multifunctional properties,the micro-nano structure of lead iodide and defects in perovskite film are modulated,so as to improve the crystallizability and electronic quality of perovskite film.In addition,we also reveal the influence of transamination reaction on the stability of isopropyl alcohol-based cationic ink,and find that can be markedly ameliorate by substituting cationic solvent with less-reactive n-butanol.Based on this integration strategy,the two-step sequential printing process of perovskite films is fully compatible with ambient preparation.The resultant devices achieve efficiency of 21.09%(0.04 cm~2),and 20.20%(1 cm~2),showing low efficiency loss at printing-area enlargement,and simultaneous present superior operational stability.This integrating optimization idea is expected to promote the practical application of two-step sequential ambient printing process.