Laboratory of Photomolecular Science, Institute of Chemical Sciences Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, EPFL, CH-1015 Lausanne, Switzerland.
Science. 2020 Oct 2;370(6512). doi: 10.1126/science.abb8985.
Mixtures of cations or halides with FAPbI (where FA is formamidinium) lead to high efficiency in perovskite solar cells (PSCs) but also to blue-shifted absorption and long-term stability issues caused by loss of volatile methylammonium (MA) and phase segregation. We report a deposition method using MA thiocyanate (MASCN) or FASCN vapor treatment to convert yellow δ-FAPbI perovskite films to the desired pure α-phase. NMR quantifies MA incorporation into the framework. Molecular dynamics simulations show that SCN anions promote the formation and stabilization of α-FAPbI below the thermodynamic phase-transition temperature. We used these low-defect-density α-FAPbI films to make PSCs with >23% power-conversion efficiency and long-term operational and thermal stability, as well as a low (330 millivolts) open-circuit voltage loss and a low (0.75 volt) turn-on voltage of electroluminescence.
阳离子或卤化物与 FAPbI（FA 是甲脒）的混合物可提高钙钛矿太阳能电池（PSC）的效率，但也会导致挥发性甲铵（MA）损失和相分离引起的吸收蓝移和长期稳定性问题。我们报告了一种使用 MA 硫氰酸盐（MASCN）或 FASCN 蒸汽处理的沉积方法，可将黄色 δ-FAPbI 钙钛矿薄膜转化为所需的纯 α 相。NMR 定量确定了 MA 掺入到框架中。分子动力学模拟表明，SCN 阴离子在热力学相变温度以下促进了 α-FAPbI 的形成和稳定。我们使用这些低缺陷密度的 α-FAPbI 薄膜制作了 PSC，其功率转换效率超过 23%，具有长期的工作和热稳定性，以及低（330 毫伏）开路电压损失和低（0.75 伏）电致发光开启电压。
