Acta Chimica Sinica ›› 2024, Vol. 82 ›› Issue (9): 971-978.DOI: 10.6023/A24030093 Previous Articles     Next Articles

Article

CsPbIBr2钙钛矿太阳能电池湿度稳定机制研究

张林a,b, 张慧a,b, 朱从潭a,b, 郭学益a,b, 杨英a,b,*()   

  1. a 中南大学冶金与环境学院 长沙 410083
    b 有色金属资源循环利用湖南省重点实验室 长沙 410083
  • 投稿日期:2024-07-01 发布日期:2024-08-15
  • 基金资助:
    国家重点研发计划项目(2023YFC3906103); 湖南省自然科学基金(2022JJ30757)

Investigation of Humidity Stabilization Mechanism in CsPbIBr2 Perovskite Solar Cells

Lin Zhanga,b, Hui Zhanga,b, Congtan Zhua,b, Xueyi Guoa,b, Ying Yanga,b,*()   

  1. a School of Metallurgy and Environment, Central South University, Changsha 410083, China
    b Hunan Key Laboratory of Nonferrous Metal Resources Recycling, Changsha 410083, China
  • Received:2024-07-01 Published:2024-08-15
  • Contact: *E-mail: muyicaoyang@csu.edu.cn; Tel.: 0731-88877863
  • Supported by:
    National Key R&D Program of China(2023YFC3906103); Natural Science Foundation of Hunan Province(2022JJ30757)

The stability and reproducibility of perovskite solar cells (PSCs) are sensitive to fabrication environment, particularly moisture. Understanding the impact of moisture during perovskite film formation is essential for developing effective strategies to enhance performance. Herein, we have systematically investigated the influence of moisture on perovskite film formation as well as photovoltaic properties under varying humidity conditions. It is found that air humidity rapidly alters the physical and thermodynamic properties of the precursor solution during film formation, influencing both the crystallization process and compositional reactions. In the absence of humidity, films primarily forms CsI-PbBr2•DMSO complexes through the reaction of CsI and PbBr2•2DMSO clusters, which transform into desired α-phase after annealing at 280 ℃. Under humid conditions, H2O competes with DMSO to coordinate with PbBr2, forming PbBr2•DMSO--H2O clusters. Additionally, H2O enhances the mobility of CsI within the wet film, leading to a phase transition to α-phase even at 40 ℃. Increased environmental humidity beyond RH 40% further accelerates the precipitation of PbBr2•DMSO--H2O complexes, leading to the formation of 2PbBr2•2DMSO--H2O. The interaction between CsI and these complexes creates larger intermediate crystals that are difficult to transform into 3D perovskites. And the complexes grow away from the substrate because of an additional solid-solid interfacial energy barrier between the crystals and the substrate. Thus, perovskite thin film becomes discontinuous, existing as crystal networks and islands, resulting in decreased coverage of the perovskite films. As a result, short-circuit current density and open-circuit voltage decrease, leading a decline in power conversion efficiency (PCE) from 10.79% at RH 0% down to 0.10% at RH 60%. In the presence of adsorbed water, O2 forms O2− at the surface of perovskite films, reacting with Pb0 defects and its components within the film to produce lead oxide (PbO). This product enhances the stability of the crystal phase, allowing PSCs prepared under RH 40% to maintain 96% of its initial efficiency even after 1656 h in ambient air (RH≤20%). During film aging, moisture in the environment causes α-CsPbIBr2 to initially transform from (100) and (200) facets to (110) facets, and then further to the δ-phase. Therefore, isolating water and oxygen effectively prevents phase transition. The insights gained from this study on the effects of humidity provide valuable guidance for controlling humidity during perovskite film preparation and storage, ultimately contributing to enhanced stability and performance.

Key words: CsPbIBr2, perovskite solar cells, moisture effect, phase transition, crystallization promotion