甲脒基卤化物钙钛矿薄膜的相稳定性

Phase transition stability of formamidine(FA)-based perovskite films

甲脒基卤化物钙钛矿(FAPbI_(3))太阳电池具有光生载流子寿命长、光电转换效率高等优点,是目前光伏领域的研究热点.然而,在室温条件下,FAPbI_(3)的相稳定性差,会从具有光电活性的立方α相逐渐转变为非活性的六方δ相,是限制卤化物钙钛矿太阳电池发展的难题之一.本文研究了不同温度条件下FAPbI3薄膜的相变行为,发现其相稳定性主要受过冷度和离子热运动两种因素的影响,在80℃条件下的相稳定性明显高于20℃的结果.与传统A位掺杂替代FA^(+)和X位掺杂替代I^(-)方法不同,本文采取B位掺杂以Eu2+替代Pb^(2+),发现掺杂的薄膜样品的光吸收谱、晶格衍射峰、光致发光等结构与光学特性的稳定性都得到明显提升,表明该B位掺杂可以有效提高FAPbI_(3)光电活性α相的稳定性.本文结果为FAPbI3钙钛矿的相稳定性研究提供了新的研究思路.

Owing to their remarkable power conversion efficiencies and thermal stability at high temperature,FAPbI3 solar cells are one of the hot topics in photovoltaic field.However,α-FAPbI_(3) shows poor phase stability at room temperature that photoactiveα-phase will gradually transform to non-photoactiveδ-phase,which limits the development of FAPbI3 solar cells.We study the phase change behavior of FAPbI_(3) films at various temperatures,and find that the phase stability is affected by the sub-cooling degree and atomic migration rate.The phase stability at 80℃is significantly better than the result at 20℃.In contrast to A site or X site doping strategy,we effectively enhance the stability of photoactiveα-FAPbI_(3) by substituting Pb2+with the Eu^(2+)on B site,and find that the optical absorption spectrum,lattice diffraction peaks,photoluminescence and other structure and optical characteristics of the doped film samples have been significantly improved,indicating that the B-site doping can effectively improve the stability of the photoelectric activeα-phase of FAPbI3.This work provides the new ideas to improve the phase stability ofα-FAPbI3.