| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 104 === Perovskite solar cells nowadays attract extensive attentions in scientific research because of its explosive improvement of power conversion efficiency from 3.81 ~ 22.1% merely in seven years. However, long term stability of perovskite solar cell is still a critical problem for practical application. Toward this end, there have been several research groups devoted to investigate the stability and degradation mechanism of perovskite solar cell.
Herein, we developed two kinds of in situ techniques including X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) to investigate the change of the crystal structure and chemical state of CH3NH3PbI3. Furthermore, the in situ XRD system was equipped with source meter and real-time solar irradiation to observe correlation between the crystallographic structure of perovskite and the evolution of solar cell performance. We observed when the solar cell worked under low humidity condition, the power conversion efficiency (PCE) decreased in three steps and the crystallographic structure of perovskite gradually transformed into PbI2. However, when we conducted the measurements under high humidity condition, the PCE dropped dramatically in just merely few minutes and the perovskite transformed into PbI2 immediately following convert to PbIOH in the end. This is the first time we found the new phase PbIOH generated and investigated the perovskite solar cell degradation mechanism under real-time solar irradiation combined with X-ray diffraction analysis.
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