Resolving Hysteresis in Perovskite Solar Cells with Rapid Flame-Processed Cobalt-Doped TiO2

Jung Kyu Kim, Sung Uk Chai, Yongfei Ji, Ben Levy-Wendt, Suk Hyun Kim, Yeonjin Yi, Tony F. Heinz, Jens K. Nørskov, Jong Hyeok Park, Xiaolin Zheng

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Abstract

To further increase the open-circuit voltage (V oc) of perovskite solar cells (PSCs), many efforts have been devoted to doping the TiO2 electron transport/selective layers by using metal dopants with higher electronegativity than Ti. However, those dopants can introduce undesired charge traps that hinder charge transport through TiO2, so the improvement in the V oc is often accompanied by an undesired photocurrent density–voltage (J–V) hysteresis problem. Herein, it is demonstrated that the use of a rapid flame doping process (40 s) to introduce cobalt dopant into TiO2 not only solves the J–V hysteresis problem but also increases the V oc and power conversion efficiency of both mesoscopic and planar PSCs. The reasons for the simultaneous improvements are two fold. First, the flame-doped Co-TiO2 film forms Co-Ov (cobalt dopant-oxygen vacancy) pairs and hence reduces the number density of Ti3+ trap states. Second, Co doping upshifts the band structure of TiO2, facilitating efficient charge extraction. As a result, for planar PSCs, the flame doping of Co increases the efficiency from 17.1% to 18.0% while reducing the hysteresis from 16.0% to 1.7%. Similarly, for mesoscopic PSCs, the flame doping of Co increases the efficiency from 18.5% to 20.0% while reducing the hysteresis from 7.0% to 0.1%.

Original languageEnglish
Article number1801717
JournalAdvanced Energy Materials
Volume8
Issue number29
DOIs
Publication statusPublished - 2018 Oct 15

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All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

Cite this

Kim, J. K., Chai, S. U., Ji, Y., Levy-Wendt, B., Kim, S. H., Yi, Y., Heinz, T. F., Nørskov, J. K., Park, J. H., & Zheng, X. (2018). Resolving Hysteresis in Perovskite Solar Cells with Rapid Flame-Processed Cobalt-Doped TiO2 Advanced Energy Materials, 8(29), [1801717]. https://doi.org/10.1002/aenm.201801717