Li Cheng, Guerrero Antonio, Zhong Yu, Gräser Anna, Luna Carlos Andres Melo, Köhler Jürgen, Bisquert Juan, Hildner Richard, Huettner Sven
Organic and Hybrid Electronics, Macromolecular Chemistry I, University of Bayreuth, Universitätstr. 30, 95447, Bayreuth, Germany.
Institute of Advanced Materials (INAM), Universitat Jaume I, 12006, Castellö, Spain.
Small. 2017 Nov;13(42). doi: 10.1002/smll.201701711. Epub 2017 Sep 25.
Organic-inorganic metal halide perovskites (e.g., CH NH PbI Cl ) emerge as a promising optoelectronic material. However, the Shockley-Queisser limit for the power conversion efficiency (PCE) of perovskite-based photovoltaic devices is still not reached. Nonradiative recombination pathways may play a significant role and appear as photoluminescence (PL) inactive (or dark) areas on perovskite films. Although these observations are related to the presence of ions/defects, the underlying fundamental physics and detailed microscopic processes, concerning trap/defect status, ion migration, etc., still remain poorly understood. Here correlated wide-field PL microscopy and impedance spectroscopy are utilized on perovskite films to in situ investigate both the spatial and the temporal evolution of these PL inactive areas under external electric fields. The formation of PL inactive domains is attributed to the migration and accumulation of iodide ions under external fields. Hence, we are able to characterize the kinetic processes and determine the drift velocities of these ions. In addition, it is shown that I vapor directly affects the PL quenching of a perovskite film, which provides evidence that the migration/segregation of iodide ions plays an important role in the PL quenching and consequently limits the PCE of organometal halide-based perovskite photovoltaic devices.
有机-无机金属卤化物钙钛矿（例如CH₃NH₃PbI₃Cl）成为一种很有前景的光电器件材料。然而，基于钙钛矿的光伏器件的功率转换效率（PCE）仍未达到肖克利-奎塞尔极限。非辐射复合途径可能起重要作用，并在钙钛矿薄膜上表现为光致发光（PL）不活跃（或暗）区域。尽管这些观察结果与离子/缺陷的存在有关，但关于陷阱/缺陷状态、离子迁移等潜在的基本物理和详细微观过程仍知之甚少。在这里，相关的宽场PL显微镜和阻抗谱被用于钙钛矿薄膜，以原位研究这些PL不活跃区域在外部电场下的空间和时间演变。PL不活跃域的形成归因于外部电场下碘离子的迁移和积累。因此，我们能够表征动力学过程并确定这些离子的漂移速度。此外，研究表明碘蒸气直接影响钙钛矿薄膜的PL猝灭，这为碘离子的迁移/偏析在PL猝灭中起重要作用并因此限制基于有机金属卤化物的钙钛矿光伏器件的PCE提供了证据。
