Song Jung Hoon, Mai Xuan Dung, Jeong Sohee, Kim Yong-Hyun
Graduate School of Nanoscience and Technology (GSNT) and Department of Physics, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, Republic of Korea.
Nano-Convergence Systems Research Division, Korea Institute of Machinery and Materials (KIMM) , Daejeon 34103, Republic of Korea.
J Phys Chem Lett. 2017 Nov 2;8(21):5259-5263. doi: 10.1021/acs.jpclett.7b02350. Epub 2017 Oct 16.
Organic-inorganic hybrid photovoltaics (PVs) have recently attracted considerable attention as their PV performance has rapidly improved. Abnormal current-voltage (I-V) characteristics or I-V hysteresis, however, were occasionally observed in such systems that hampered the development of the PV technology. Here we study the hysteresis of organic-inorganic hybrid colloidal quantum dot (CQD) PVs by analyzing I-V characteristics upon systematic modulation of organic components of CQDs. We demonstrate that an external bias stress to CQD films transiently prompts redistribution of mobile ions, particularly protons of surface ligands, thus leading to the formation of a transient space-charge region in the CQD films. The variable space-charge region causes I-V hysteresis and photoinstability of CQD PVs, which is closely correlated with the transient behavior of mobile ions. Our findings here could provide significant implications to the understanding of the influence of mobile ions on I-V hysteresis in other organic-inorganic hybrid PVs such as perovskites.
有机-无机杂化光伏电池（PVs）近来因其光伏性能迅速提升而备受关注。然而，在这类系统中偶尔会观察到异常的电流-电压（I-V）特性或I-V滞后现象，这阻碍了光伏技术的发展。在此，我们通过分析在对胶体量子点（CQD）的有机成分进行系统调制时的I-V特性，研究有机-无机杂化CQD光伏电池的滞后现象。我们证明，对CQD薄膜施加外部偏置应力会瞬时促使移动离子，特别是表面配体的质子重新分布，从而导致在CQD薄膜中形成一个瞬态空间电荷区。可变的空间电荷区导致CQD光伏电池出现I-V滞后和光不稳定性，这与移动离子的瞬态行为密切相关。我们在此的发现对于理解移动离子对其他有机-无机杂化光伏电池（如钙钛矿电池）中I-V滞后的影响可能具有重要意义。
