期刊
JOURNAL OF MATERIALS CHEMISTRY A
卷 9, 期 12, 页码 7575-7585出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/d0ta12458c
关键词
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资金
- Ministry of Science and Technology of China [2016YFA0200700]
- Chinese Academy of Sciences [YJKYYQ20180029, CAS-ITRI 2019010, 2020VCA0012]
- Jiangsu Science and Technology Program [BX2019111]
- Doctoral Network in Materials Research at Abo Akademi University
- Swedish Cultural Foundation in Finland
This study demonstrates the oxidation mechanism of Spiro-OMeTAD in perovskite solar cells using various analysis methods, and confirms the involvement of Li+ migration in the oxidation process.
n-i-p Type perovskite solar cells generally require air oxidation of the Spiro-OMeTAD layer to achieve high power conversion efficiency (PCE). However, the detailed oxidation mechanism is still not fully understood. In this paper, oxidation of Spiro-OMeTAD was demonstrated via a non-contact electrochemical route using UV-Vis absorption, laser beam induced current (LBIC) imaging and secondary ion mass spectrometry (SIMS) profiling of the Spiro-OMeTAD films. At the cathode, oxygen is reduced to form OH- with the help of H2O, while the anodic reaction is the oxidation of Spiro-OMeTAD to form Spiro-OMeTAD(+). Diffusion of Li+ towards the surface of the Ag electrode completes the electrochemical cycle and increases the conductivity of the hole-transporting layer. SIMS analyses of the completed devices demonstrate that the oxidation of Spiro-OMeTAD also leads to migration of Li+ through the perovskite layer into SnO2, which supposedly leads to an increase of the built-in voltage. We verify these results by incorporation of the experimentally measured Li+ concentration into a numerical drift-diffusion simulation, to replicate solar cell J-V-curves. This work provides a new insight into the oxidation of Spiro-OMeTAD in perovskite solar cells, and demonstrates that Li+ migration is involved in the oxidation of Spiro-OMeTAD.
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