Electron and hole transfer at TiO2/perovskite and perovskite/spiro-OMeTAD interfaces in the triple cation perovskite solar cells prepared under room ambient conditions
Katarzyna Pydzńska-Białek a, Viktoriia Drushliak a, Emerson Coy b, Karol Załęski b, Jessica Flach c d, Jesus Idigoras e, Lidia Contreras-Bernal e, Anders Hagfeldt c, Juan Anta e, Marcin Ziółek a
a Adam Mickiewicz University Poznań, Poland, Uniwersytetu Poznańskiego 2, Poznań, Poland
b NanoBioMedical Centre, Adam Mickiewicz University, PL, Wszechnicy Piastowskiej, 3, Poznań, Poland
c Ecole Polytechnique Fédérale de Lausanne EPFL, Laboratory of Photomolecular Science, Institute of Chemical Sciences and Engineering, Station, 6, Lausanne, Switzerland
d University of Wisconsin-Madison, 1101 University Avenue, Madison, 53703, United States
e Pablo de Olavide University, Sevilla, Spain, Carretera de Utrera, km. 1, Montequinto, Spain
Proceedings of International Conference on Impedance Spectroscopy and Related Techniques in Metal Halide Perovskites (PERIMPED)
Online, Spain, 2020 October 6th - 7th
Organizers: Juan Bisquert, Bruno Ehrler and Eline Hutter
Oral, Katarzyna Pydzńska-Białek, presentation 003
Publication date: 25th September 2020

The perovskite solar cells have been extensively developed since 2009 but still the ultrafast and fast processes occurring at the interfaces in this system are not fully understood. We focused on the investigation of electron transport paths: after light absorption, an electron is promoted from the valence to the conduction band, and then several processes can occur. First few hundreds of femtosecond after light absorption are governed by cooling of the hot carriers. When the process is finished, sharp bleach due to the band filling phenomena occurs at absorption edge in the transient absorption measurements. Its decay correlates with photoluminescence kinetics and represents the excited carrier lifetime [1,2]. That decay proceeds by several paths such as the recombination (first-, second- and third-order) and the charge injection to an electron transporting material (ETM) or a hole transporting material (HTM).       

In this work we focused on a triple cation perovskite FA0.76MA0.19Cs0.05(I0.81Br0.19)3 sandwiched between a spiro-OMeTAD (HTM) and mesoporous TiO2 (ETM) layers prepared under ambient (in the presence of oxygen and ambient room humidity) conditions. The studies were based on femtosecond to nanosecond transient absorption, picosecond to nanosecond time-resolved emission, electrochemical impedance spectroscopy and x-ray diffraction measurements of the prepared cells. By properly tuning the excitation wavelength, changing the excitation side and grazing angles we were able to selectively probe the titania/perovskite or perovskite/spiro-OMeTAD interfaces of the cells.

Difference in PbI2 content as well as difference in charge dynamics on the ETM and HTM interface were detected. The transient bleach and stationary emission band maximum was also shifted when HTM or ETM side was investigated. We also checked influence of DMSO content in the precursor solution on the cell parameters. We found that higher DMSO concentration causes an increase of the ideality factor in electrochemical impedance studies [3].

The study was supported by Polish Ministry of Science and Higher Education (Ministerstwo Nauki i Szkolnictwa Wyższego) under project “Diamentowy Grant” 0019/DIA/2017/46.

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