Hole-Transport Interlayers for Planar Perovskite Solar Cells
Lucia Nicoleta Leonat a, Andrei Tomulescu a, Bekele Teklemariam Hailegnaw b, Florentina Neatu a, Mihaela Florea a, Viorica Stancu a, Markus Clark Scharber b, Stefan Antohe c d, Lucian Pintilie a
a National Institute for Materials Physics, Atomistilor 405A, 077125, Magurele, Ilfov, Romania
b Johannes Kepler University Linz, Austria, Altenbergerstraße, 69, Linz, Austria
c University of Bucharest, Faculty of Physics, Department of Electricity and Biophysics, Strada Atomiștilor, Măgurele, Romania
d Academy of Romanian Scientists, Bucarest 030167, Rumanía, Bucarest, Romania
nanoGe Perovskite Conferences
Proceedings of International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics (NIPHO20)
Sevilla, Spain, 2020 February 23rd - 25th
Organizer: Hernán Míguez
Poster, Lucia Nicoleta Leonat, 084
Publication date: 25th November 2019

Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is one of the most common conducting polymers in hybrid and organic electronics. Its ease of processing and low toxicity is accompanied by the high conductivity, high optical transparency, mechanical flexibility but most importantly, it enables low temperature electronic device fabrication, hence the use of flexible plastic substrates [1]. However, despite all these benefits, its acidic nature is highly detrimental to any other adjacent materials within photovoltaic devices, especially the organic photoactive materials for solar cells or even the indium tin oxide (ITO) electrode [2,3]. Additionally, there is an energetic mismatch between the energy levels of PEDOT:PSS and mixed-halide perovskite, limiting efficient charge extraction at this interface resulting low open circuit voltage (Voc) and short circuit current (Jsc) in solar cells. One approach to improve the charge dynamics at this interface is to use a buffer layer that can lower the hole injection barrier and prevent the non-radiative exciton quenching. For this purpose we chose two polymers: poly(N-vinylcarbazole) (PVK) and poly2,7-9,9-di-n-octylfluorene-alt-1,4-phenylene-4-sec-butylphenylimino-1,4-phenylene (TFB).

The effect of intermediary thin p-type polymer layers placed between the hole-transporting layer PEDOT:PSS and the active layer within mixed-halide perovskite solar cells (HPSCs) is studied herein. Our work was focused on studying the quality of the perovskite layer on top of these layers by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), XRD as well as on the charge dynamics at the holes-transporting interface by photoluminescence spectroscopy (PL) and X-ray photoelectron spectroscopy (XPS). We find that the perovskite settles well, compactly and without pinholes on all polymers. The photoluminescence spectra indicate the excitonic quenching for all polymers, including for the perovskite deposited only on PEDOT:PSS. However, there are slight differences where the effect is more pronounced for samples with PVK interlayer. These results are in good agreement with the photovoltaic parameters measured for the corresponding HPSCs.

The authors acknowledge funding through projects PN-III-P1-1.1-PD-2016-0703, PN 177/2017 and the Core Program PN19-03 from the Romanian Ministry of Research and Innovation.

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