Synergetic effects of electrochemical oxidation of Spiro-OMeTAD and Li+ion migration for improving the performance of n-i-p type perovskite solar cells

Changzeng Ding, Rong Huang, Christian Ahläng, Jian Lin, Lianping Zhang, Dongyu Zhang, Qun Luo, Fangsen Li, Ronald Österbacka*, Chang Qi Ma

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

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 demonstratedviaa 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 OHwith 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 cellJ-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.

Original languageEnglish
Pages (from-to)7575-7585
Number of pages11
JournalJournal of Materials Chemistry A
Volume9
Issue number12
DOIs
Publication statusPublished - 28 Mar 2021
MoE publication typeA1 Journal article-refereed

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