氯掺杂甲胺基钙钛矿电池的性能及其改进

Properties and improvements of chlorine-doped methylamine-based perovskites

金属卤化物钙钛矿由于其高吸收系数、长距离载流子扩散长度和可调带隙,近年来在太阳能电池等光电器件中得到了广泛应用,有望实现商业应用.甲胺铅碘(MAPbI_(3))作为一种标准的钙钛矿化合物组分已得到了充分的研究,然而,湿化学法制备的多晶薄膜由于其低形成能通常会产生较多的晶体缺陷(包含界面和晶界处缺陷),这是导致相变的一个重要原因,因此降低材料中的缺陷密度是提高钙钛矿稳定性的一个重要手段.虽然缺陷钝化是制备高效钙钛矿太阳能电池最常用的方法之一,但是分子钝化基团与钙钛矿晶体之间相对较弱的二次键可能会给实际设备的应用带来困难,特别是在高温、潮湿和紫外线(UV)光等恶劣环境下操作时.另一种策略是通过调控卤化物组成来提高其本征结构稳定性.本文以氯甲胺(MACl)和碘化铅(PbI_(2))作为前驱体通过一步旋涂法制备了两相钙钛矿(MAPbI_(2)Cl).结果表明,氯离子掺杂替代部分碘离子可以更好地诱导钙钛矿结晶,进而稳定MAPbI_(3)晶格.经过Cl掺杂的钙钛矿层表现出更低的缺陷态密度,对比于原始薄膜,Cl的载流子寿命增加了7倍,与此同时,功率转换效率(PCE)和操作稳定性都得到了很大的改善,PCE从11.41%提高到13.68%.器件具有良好的操作稳定性,在最大功率点输出8000 s后并未显示出明显的衰减.本文为制备高效稳定的钙钛矿太阳能电池提供了全新的思路.

Metal halide perovskite(MHP)has been widely used in optoelectronic devices such as solar cells in recent years due to their high absorption coefficients,long-range charge carrier diffusion lengths,and adjustable band gap,which is expected to achieve commercial application.Methylammonium lead iodide(MAPbI_(3)) has been fully investigated as a standard perovskite component,however,due to the low formation energy of polycrystalline films fabricated by wet chemical method,crystal defects(including interface and grain boundary defects)are generally inevitable,which is a principal factor leading to phase transition.Therefore,reducing the defect density of perovskite is a prominent approach to improve the stability of perovskite.Although defect passivation is one of the most commonly used methods to fabricate efficient perovskite solar cells(PSCs),the relatively weak secondary bond between molecular passivation group and perovskite crystal may bring difficulties to the application of practical devices,particularly when operating under harsh environments,such as high temperature,humidity,and ultraviolet light.Therefore,improving the intrinsic structure stability of the perovskite via changing its composition can be an effective way.Although perovskites containing chlorine precursors have been empolyed in solar cells device,how chloride ions affect the structural and electronic properties of these films was not understood yet.In this work,two-phase perovskite(MAPbI_(2)Cl) was fabricated by one-step spin coating with methylamine chloride(MACl)and lead iodide(PbI_(2)) as precursors.As a result,chloride(Cl)doping can superiorly induce perovskite crystallization and thus stabilize the MAPbI_(3) lattice.The Cl doped perovskite layer shows lower defect density,and compared with the original MAPbI_(3) film,the carrier lifetime of MAPbI_(2)Cl is increased by 7 times.Simultaneously,both of PCE and operational stability have been largely improved with PCE increased from 11.41%to 13.68%.There is no obvious degradation in the maximum power point output for nearly 8000 seconds in ambient conditions.