Zhang Teng, Cheung Sin Hang, Meng Xiangyue, Zhu Lei, Bai Yang, Ho Carr Hoi Yi, Xiao Shuang, Xue Qingzhong, So Shu Kong, Yang Shihe
Nano Science and Technology Program, Department of Chemistry, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong.
Department of Physics and Institute of Advanced Materials, Hong Kong Baptist University , Kowloon Tong, Hong Kong SAR, P. R. China.
J Phys Chem Lett. 2017 Oct 19;8(20):5069-5076. doi: 10.1021/acs.jpclett.7b02160. Epub 2017 Oct 4.
The light soaking effect (LSE) is widely known in perovskite solar cells (PVSCs), but its origin is still elusive. In this study, we show that in common with hysteresis, the LSE is owed to the ion migration in PVSCs. Driven by the photovoltage, the mobile ions in the perovskite materials (MA/I) migrate to the selective contacts, forming a boosted P-i-N junction resulting in enhanced charge separation. Besides, the mobile ions (MA) can soften and suture the PCBM/perovskite interface and thus reduce the trap density, in keeping with a higher open-circuit voltage. Finally, almost LSE-free PVSCs can be prepared by using 0.1 wt % MAI-doped PCBM as the electron transport material, whereas overdoping (1 wt % MAI doping) makes the LSE even more pronounced due to excess mobile ions that need time to migrate to reach a new quasi-static state.
光浸泡效应（LSE）在钙钛矿太阳能电池（PVSCs）中广为人知，但其起源仍不清楚。在本研究中，我们表明，与滞后现象一样，LSE归因于PVSCs中的离子迁移。在光电压的驱动下，钙钛矿材料（MA/I）中的移动离子迁移到选择性接触层，形成增强的P-i-N结，从而增强电荷分离。此外，移动离子（MA）可以软化并缝合PCBM/钙钛矿界面，从而降低陷阱密度，与更高的开路电压一致。最后，通过使用0.1 wt% MAI掺杂的PCBM作为电子传输材料，可以制备几乎无LSE的PVSCs，而过量掺杂（1 wt% MAI掺杂）会使LSE更加明显，这是由于过量的移动离子需要时间迁移以达到新的准静态状态。
