A research paper titled "Perovskite facet heterojunction solar cells" was published in the journal Joule by the team of Zhao Qing from Peking University and Yi Chenyi from Tsinghua University. Gao Feng is the first author, and Professor Zhao Qing and Yi Chenyi are co-corresponding authors.
Key Highlights: This paper first constructed a facet heterojunction by integrating two thin films with different crystal planes (001)/(111) in a perovskite photovoltaic device. Combining the advantages of the (001) and (111) facet orientations of perovskite, it achieved high efficiency (24.92%) and high operational stability (2000 hours) of perovskite solar cells prepared by evaporation. After 2000 hours of operation at maximum power output, the initial performance of the target device was maintained at 91.7%, significantly improving its operational stability.
The surface of polycrystalline perovskite films has different facet orientations, which lead to diverse chemical and electronic structures. These changes in facet orientation are reflected in differences in optoelectronic properties, including energy level arrangement and carrier mobility. Heterojunction structures are fundamental elements in conventional photovoltaic devices, involving the strategic combination of two distinct components with unique optoelectronic properties. Heterogeneity in optoelectronic properties along different facet orientations provides opportunities for creating junctions that can enhance device performance.
Based on this, the research team of Qing Zhao from Peking University and Chenyi Yi from Tsinghua University constructed a double-faceted heterojunction (FHJ) in perovskite-based photovoltaic devices by integrating two thin films exhibiting different crystal planes (001)/(111). The buried interface of the FHJ device exhibits an effective type-II band alignment, which facilitates the separation and extraction of photoinduced carriers, thereby reducing carrier recombination losses. The FHJ improved the power conversion efficiency (PCE) of evaporated perovskite solar cells (PSCs) to 24.92%. After 2000 hours of operation at maximum power output, the target device retained 91.7% of its initial performance, significantly improving its operational stability. In addition, the FHJ device achieved improved operational stability and resistance to humidity and photothermal degradation.
This study demonstrates that FHJ plays a key role in improving carrier transport efficiency and reducing carrier recombination through type-II energy level alignment, contributing to the superior performance of photovoltaic devices, thereby broadening the horizons for future sustainable energy solutions. It also provides a new approach to exploit the advantages of perovskites with different facet orientations.
Source：
https://doi.org/10.1016/j.joule.2024.11.004