The impact of spiro-OMeTAD photodoping on the reversible light-induced transients of perovskite solar cells
Tan, Boer (Monash University. Department of Chemical Engineering)
Raga, Sonia (Institut Català de Nanociència i Nanotecnologia)
Rietwyk, Kevin James (Monash University. Department of Chemical Engineering)
Lu, Jianfeng (Monash University. Department of Chemical Engineering)
Fürer, Sebastian O. (Monash University. ARC Centre of Excellence in Exciton Science)
Griffith, James C. (Monash University. Monash X-ray Platform)
Cheng, Yi-Bing (Wuhan University of Technology. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing)
Bach, Udo (Monash University. ARC Centre of Excellence in Exciton Science)

Fecha:	2021
Resumen:	Hole transporting materials (HTMs) play essential roles in facilitating hole extraction and suppressing recombination in lead halide perovskite solar cells (PSCs). High levels of p-doping in HTMs is necessary for achieving high device performance, attributed to an increased electrical conductivity. In this work, we provide evidences that the poor performance of PSCs with low levels of doping (i. e. , 4 mol% spiro-OMeTAD) in spiro-OMeTAD is mainly caused by the presence of a Schottky barrier at the perovskite/spiro-OMeTAD interface, hampering hole injection. Under continuous illumination at open-circuit condition, the barrier gradually diminishes, increasing the PSC power conversion efficiency by 70-fold after 7 h. This process is completely reversible, returning to the initial poor performance after dark storage. We attribute this improvement in performance to a gradual photodoping of spiro-OMeTAD, triggered by the transfer of photogenerated holes and mediated by the slow migration of halide anions from perovskite to compensate the newly formed spiro-OMeTAD. In-situ parallel analyses with impedance spectroscopy (IS) and photoluminescence are employed to gain insights into the charge dynamics along with light soaking. We find that the Schottky barrier resistance overlays with the recombination signal at the high frequency arc of IS, having important implications for the IS data analysis for PSCs. The work elucidates a major mechanism causing the slow efficiency variations during light/dark cycling, commonly observed in PSCs, which complicates the determination of long-term stability.
Nota:	Ajuts: Sonia R. Raga acknowleges the support from "la Caixa" Foundation (ID 100010434) with fellowship code LCF/BQ/PI20/11760024 for funding part of this research.
Derechos:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, i la comunicació pública de l'obra, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original. No es permet la creació d'obres derivades.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió acceptada per publicar
Materia:	Spiro-OMeTAD ; Impedance spectroscopy ; Photodoping ; Hole injection barrier ; Light Soaking
Publicado en:	Nano Energy, Vol. 82 (April 2021) , art. 105658, ISSN 2211-2855

DOI: 10.1016/j.nanoen.2020.105658

Postprint 27 p, 1.2 MB

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