School of Materials, University of Manchester, Manchester, M13 9PL, UK.
Phys Chem Chem Phys. 2018 Nov 14;20(44):27959-27969. doi: 10.1039/c8cp05148h.
Microgels (MGs) are crosslinked polymer colloid particles that swell in a good solvent. Although MGs have been studied for over 80 years their ability to control the morphology and optoelectronic properties of composite films containing photoactive materials is in its infancy. Solution processable hybrid organic-inorganic perovskites such as CH3NH3PbI3-zClz have attracted enormous fundamental and applied interest because of their outstanding optoelectronic properties. There is considerable interest in establishing methods to control perovskite film morphology, for example, using micropatterning. Here, hydrophilic poly(N-vinylformamide)-based MGs were dispersed in perovskite precursor solution which was then spin coated to deposit CH3NH3PbI3-zClz/MG films for the first time. Remarkably, the CH3NH3PbI3-zClz/MG composites formed disordered inverse opal (DIO) films. The CH3NH3PbI3-zClz/MG composition ranges which gave DIO films are identified using a phase diagram. The pore wall thickness is shown to be controlled by the volume fraction of MGs used and a simple model is presented to explain this behaviour. The MGs not only caused CH3NH3PbI3-zClz to be more efficiently deposited but also increased light absorption and photoluminescence intensity. Demonstration solar cells constructed containing the DIO CH3NH3PbI3-zClz/MG films had an average conversion efficiency of 6.58 ± 0.81%. A mechanism for DIO film formation is discussed. The principles established in this study wherein MGs control the morphology and properties of CH3NH3PbI3-zClz/MG films should also apply to other perovskite/MG composites.
微凝胶（MGs）是交联聚合物胶体颗粒，在良溶剂中溶胀。尽管 MGs 已经研究了 80 多年，但它们控制含有光活性材料的复合薄膜形态和光电性能的能力还处于起步阶段。可溶液加工的混合有机-无机钙钛矿，如 CH3NH3PbI3-zClz，由于其出色的光电性能而引起了极大的基础和应用兴趣。人们对建立控制钙钛矿薄膜形态的方法（例如使用微图案化）非常感兴趣。在这里，亲水性的基于聚（N-乙烯基甲酰胺）的 MGs 分散在钙钛矿前驱体溶液中，然后旋涂以首次沉积 CH3NH3PbI3-zClz/MG 薄膜。值得注意的是，CH3NH3PbI3-zClz/MG 复合材料形成了无序的反蛋白石（DIO）薄膜。使用相图确定了形成 DIO 薄膜的 CH3NH3PbI3-zClz/MG 复合材料的组成范围。结果表明，孔壁厚度可以通过使用的 MGs 的体积分数来控制，并提出了一个简单的模型来解释这种行为。MGs 不仅使 CH3NH3PbI3-zClz 更有效地沉积，而且提高了光吸收和光致发光强度。所构建的包含 DIO CH3NH3PbI3-zClz/MG 薄膜的演示太阳能电池的平均转换效率为 6.58 ± 0.81%。讨论了 DIO 薄膜形成的机制。本研究中确立的原理，即 MGs 控制 CH3NH3PbI3-zClz/MG 薄膜的形态和性能，也应适用于其他钙钛矿/MG 复合材料。
