Perovskite Solar Cell Modeling using Light and Voltage Modulated Techniques
Sandheep Ravishankar a, Clara Aranda a, Sandy Sanchez b, Juan Bisquert a, Michael Saliba b, Germa Garcia-Belmonte a
a Institute of Advanced Materials (INAM), Universitat Jaume I, Castelló, Spain
b Adolphe Merkle Institute, Chemin des Verdiers 4, Fribourg, Switzerland
Proceedings of Interfaces in Organic and Hybrid Thin-Film Optoelectronics (INFORM)
València, Spain, 2019 March 5th - 7th
Organizers: Natalie Stingelin, Henk Bolink and Michele Sessolo
Poster, Sandheep Ravishankar, 099
Publication date: 8th January 2019

The analysis of the Impedance Spectroscopy data of perovskite solar cells (PSCs) has been challenging so far, with the low frequency phenomena in particular yielding ambivalent results and interpretation. We tackle this problem by carrying out Intensity Modulated Photocurrent Spectroscopy (IMPS) measurements at open circuit (OC) on CH3NH3PbBr3 cells prepared by the flash infra-red annealing method with different electron selective contacts. We identify the existence of a capacitance of the order of 10-4 F·cm-2 that is not discernible from Impedance Spectroscopy (IS) measurements, which we attribute to an accumulation of anions at the perovskite/Spiro-OMeTAD interface, which also likely includes an electronic component. This interface is a dominant recombination pathway at lower voltages and can account for the large disparity in fill factors observed in PSCs. By developing detailed models for the IMPS response at both OC and short circuit (SC) conditions, we also confirm that the arcs observed in the upper quadrant of the IMPS spectra are not related to transport times, as is commonly interpreted, but time constants formed between the series resistance and capacitors within the circuit. By combining insights from IMPS and IS measurements, we develop a more complete equivalent circuit for the PSC that can be used as a basis for coming research with different perovskite materials and contact layers.

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