Ma Fusheng, Li Jiangwei, Li Wenzhe, Lin Na, Wang Liduo, Qiao Juan
Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education , Department of Chemistry , Tsinghua University , Beijing 100084 , PR. China . Email:
Chem Sci. 2017 Jan 1;8(1):800-805. doi: 10.1039/c6sc03542f. Epub 2016 Sep 15.
Although formamidinium lead iodide (FAPbI) perovskite has shown great promise in the field of perovskite-based optoelectronic devices, it suffers the complications of a structural phase transition from a black perovskite phase (α-FAPbI) to a yellow non-perovskite phase (δ-FAPbI). Generally, it is pivotal to avoid δ-FAPbI since only α-FAPbI is desirable for photoelectric conversion and near-infrared (NIR) emission. However, herein, we firstly exploited the undesirable δ-FAPbI to enable structurally stable, pure FAPbI films with a controllable α/δ phase junction at low annealing temperature (60 °C) through stoichiometrically modified precursors (FAI/PbI = 1.1-1.5). The α/δ phase junction contributes to a striking stabilization of the perovskite phase of FAPbI at low temperature and significantly enhanced NIR emission at 780 nm, which is markedly different from pure α-FAPbI (815 nm). In particular, the optimal α/δ phase junction with FAI/PbI = 1.2 exhibited preferable long-term stability against humidity and high PLQY of 6.9%, nearly 10-fold higher than that of pure α-FAPbI (0.7%). The present study opens a new approach to realize highly stable and efficient emitting perovskite materials by utilizing the phase junctions.
尽管甲脒碘化铅（FAPbI）钙钛矿在基于钙钛矿的光电器件领域展现出了巨大潜力，但它存在从黑色钙钛矿相（α-FAPbI）到黄色非钙钛矿相（δ-FAPbI）的结构相变问题。通常，避免形成δ-FAPbI至关重要，因为只有α-FAPbI适用于光电转换和近红外（NIR）发射。然而，在此我们首次利用这种不理想的δ-FAPbI，通过化学计量比改性的前驱体（FAI/PbI = 1.1 - 1.5）在低退火温度（60°C）下制备出具有可控α/δ相结、结构稳定的纯FAPbI薄膜。α/δ相结有助于在低温下显著稳定FAPbI的钙钛矿相，并显著增强780 nm处的近红外发射，这与纯α-FAPbI（815 nm）明显不同。特别地，FAI/PbI = 1.2的最佳α/δ相结表现出对湿度的优异长期稳定性以及6.9%的高PLQY，比纯α-FAPbI（0.7%）高出近10倍。本研究通过利用相结开辟了一种实现高稳定性和高效发光钙钛矿材料的新方法。
