First-Principles Study of Ion Diffusion in Perovskite Solar Cell Sensitizers

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• 作者：Jun Haruyama ; Keitaro Sodeyama ; Liyuan Han ; Yoshitaka Tateyama
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：August 19, 2015
• 年：2015
• 卷：137
• 期：32
• 页码：10048-10051
• 全文大小：290K
• ISSN：1520-5126

文摘

Hysteresis in current鈥搗oltage curves has been an important issue for conversion efficiency evaluation and development of perovskite solar cells (PSCs). In this study, we explored the ion diffusion effects in tetragonal CH₃NH₃PbI₃ (MAPbI₃) and trigonal (NH₂)₂CHPbI₃ (FAPbI₃) by first-principles calculations. The calculated activation energies of the anionic and cationic vacancy migrations clearly show that I^{鈥?/sup> anions in both MAPbI₃ and FAPbI₃ can easily diffuse with low barriers of ca. 0.45 eV, comparable to that observed in ion-conducting materials. More interestingly, typical MA+ cations and larger FA+ cations both have rather low barriers as well, indicating that the cation molecules can migrate in the perovskite sensitizers when a bias voltage is applied. These results can explain the ion displacement scenario recently proposed by experiments. With the dilute diffusion theory, we discuss that smaller vacancy concentrations (higher crystallinity) and replacement of MA+ with larger cation molecules will be essential for suppressing hysteresis as well as preventing aging behavior of PSC photosensitizers.}