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Issue 10, 2018
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Novel p-dopant toward highly efficient and stable perovskite solar cells

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Li-TFSI is the most common p-dopant for the hole conductor spiro-MeOTAD in the normal structure (n–i–p) of perovskite solar cells (PSCs), which consistently yield the highest power conversion efficiency (PCE) albeit at the risk of lower long-term operational stability. Here we successfully replace conventional Li-TFSI with Zn-TFSI2, which not only acts as a highly effective p-dopant but also enhances considerably both the photovoltaic performance and long-term stability. The incorporation of Zn-TFSI2 as a dopant for spiro-MeOTAD leads to an increase by one order in the hole mobility compared to Li-TFSI from 3.78 × 10−3 cm2 V−1 s−1 to 3.83 × 10−2 cm2 V−1 s−1. Furthermore, the device with Zn-TFSI2 showed an 80 mV higher built-in voltage and a bigger recombination resistance than the one with Li-TFSI, which were responsible for the striking increase in both the open-circuit voltage and fill factor, leading to a stabilized PCE of 22.0% for the best cells. Remarkably, the device employing Zn-TFSI2 demonstrated superb photo-stability, showing even a 2% increase in the PCE after 600 h light soaking at the maximum power point (mpp) under full sun, while the PCE of the device with Li-TFSI decreased by 20% under the same conditions. Similarly, the device with Zn-TFSI2 showed better operational stability at 50 °C resulting in a 21% decrease in the PCE after 100 h aging at the mpp under full sun while the Li-TFSI based one showed a 55% decrease. Moreover, the Zn-TFSI2 based device was capable of effectively resisting humidity compared to the one based on Li-TFSI from shelf stability monitoring (R.H. ≥ 40%) in the dark.

Graphical abstract: Novel p-dopant toward highly efficient and stable perovskite solar cells

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Supplementary files

Article information

22 May 2018
13 Jul 2018
First published
30 Jul 2018

Energy Environ. Sci., 2018,11, 2985-2992
Article type

Novel p-dopant toward highly efficient and stable perovskite solar cells

J. Seo, H. Kim, S. Akin, M. Stojanovic, E. Simon, M. Fleischer, A. Hagfeldt, S. M. Zakeeruddin and M. Grätzel, Energy Environ. Sci., 2018, 11, 2985
DOI: 10.1039/C8EE01500G

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