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Vapor-Phase Formation of a Hole-Transporting Thiophene Polymer Layer for Evaporated Perovskite Solar Cells

: Suwa, K.; Cojocaru, L.; Wienands, K.; Hofmann, C.; Schulze, P.S.C.; Bett, A.J.; Winkler, K.; Goldschmidt, J.C.; Glunz, S.W.; Nishide, H.


ACS applied materials & interfaces 12 (2020), Nr.5, S.6496-6502
ISSN: 1944-8244
ISSN: 0013-936X
ISSN: 1944-8252
Fraunhofer ISE ()
Photovoltaik; Neuartige Photovoltaik-Technologien; Farbstoff- und Perowskitsolarzellen; Tandemsolarzellen auf kristallinem Silicium

Homogeneous layer formation on textured silicon substrates is essential for the fabrication of highly efficient monolithic perovskite silicon tandem solar cells. From all well-known techniques for the fabrication of perovskite solar cells (PSCs), the evaporation method offers the highest degree of freedom for layer-by-layer deposition independent of the substrate’s roughness or texturing. Hole-transporting polymers with high hole mobility and structural stability have been used as effective hole-transporting materials (HTMs) of PSCs. However, the strong intermolecular interactions of the polymers do not allow for a layer formation via the evaporation method, which is a big challenge for the perovskite community. Herein, we first applied a hole-transporting terthiophene polymer (PTTh) as an HTM for evaporated PSCs via an in situ vapor-phase polymerization using iodine (I2) as a sublimable oxidative agent. PTTh showed high hole mobility of 1.2 × 10–3 cm2/(V s) and appropriate energy levels as HTM in PSCs (EHOMO = −5.3 eV and ELUMO = −3.3 eV). The PSCs with the in situ vapor-phase polymerized PTTh hole-transporting layer and a co-evaporated perovskite layer exhibited a photovoltaic conversion efficiency of 5.9%, as a proof of concept, and high cell stability over time. Additionally, the polymer layer could fully cover the pyramidal structure of textured silicon substrates and was identified as an effective hole-transporting material for perovskite silicon tandem solar cells by optical simulation.