摘要
Carbon-electrode based mesoscopic perovskite solar cells (meso‑CPSCs) are known for their unique mesoporous skeleton structure. Understanding the growth dynamics of lead halide perovskite (PVSK) in the mesoporous skeleton has remained as one of the key tasks. Here in this article, we happen to observe that, air humidity could affect the growth process of PVSK in the mesoporous skeleton. When being treated at relatively higher moisture environment (RH≥70%), uneven crystallization is obtained, or PVSK tends to crystallize at the surface of carbon electrode, leaving voids at the buried interface, or that between PVSK and electron-transport-layer (ETL). Meanwhile, water molecules related intermediate PVSK phase is formed at the top part of the skeleton. In contrast, when being treated at relatively lower RH (≤30%), uniform PVSK loading is harvested in the mesoporous skeleton, leading to faster extraction of photo-generated charge carriers, and helping upgrade the average power conversion efficiency from 0.33% to 12.34%; subsequent three-step treatment and Ag deposition raise the champion PCE to 15.21%. Careful examination shows that, the uneven crystallization of PVSK correlates closely to the absolute humidity (AH) or the concentration of moisture molecules. High AH facilitates the upward transport of solute in PVSK precursor, and results in preferred crystallization in the upper region, which resembles the transpiration behavior in plants. This work reveals the importance of the control over moisture concentration during the PVSK crystallization process. Moisture molecules trigger a transpiration-like upward transport of precursor solutes, driving preferential perovskite crystallization near the carbon-electrode surface while leaving voids and poor contact at the buried perovskite/ETL interface, showing the importance of control over the humidity. Download: Download high-res image (338KB) Download: Download full-size image
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