New sulphur containing dyes to study dye-TiO2 interactions in dye-sensitised solar cells
Christopher Kershaw a, Peter Holliman a, Eurig Jones a, Diana Meza-Rojas a, Anthony Lewis a, James McGettrick a, Dawn Geatches b, Kakali Sen b, Ya-Wen Hsiao b, Sebastian Metz c, Graham Tizzard d, Simon Coles d
a Faculty of Science and Engineering, Swansea University, GB, Swansea SA2 8PP, Reino Unido, Swansea, United Kingdom
b Scientific Computing Department, STFC Daresbury Laboratory, Daresbury, Warrington, UK
c Fraunhofer Institute for Solar Energy Systems ISE, 79110 Freiburg, Germany
d UK National Crystallography Service, Chemistry, University of Southampton, University Road, Southampton SO17 1BJ, UK
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Poster, Christopher Kershaw, 194
Publication date: 20th April 2022

Typically, the regeneration of the dye in dye-sensitised solar cells (DSC) is several orders of magnitude larger than other electron transfer processes observed in DSC devices.[1] Therefore, understanding the interface between the dye and the electron charge carrier is key to achieving high efficiencies in both liquid and solid-state DSCs. Previous work has described using a sulphur heteroatom to influence dye regeneration[2–4] however, this process is still poorly understood.
This work reports the synthesis of nine novel half-squaraine (HfSQ) dyes; five containing a benzothiazole moiety and four containing an indolenine moiety. X-ray single crystal structural and characterisation data have been correlated with device data to investigate the influence of sulphur heteroatoms on dye regeneration.
Using the sulphur hetero atom as an atomic probe for resolved X-ray photoelectron spectroscopy (AR-XPS) and then comparing this data with both density functional theory (DFT) calculations of dye energy levels (e.g. HOMO and LUMO) and experimental (UV-Vis, ATR-IR and J-V) data we have been able to interpret how HfSQ dyes self-assemble and orientate themselves on the TiO2 surface.[5]
The orientation of dyes is particularly important as not only will it impact the interface between the dye and the electron charge carrier, but has a direct impact on dye loading and therefore device efficiency.

We gratefully acknowledge funding from the EPSRC EP/ P030068/1 (PJH, DMR), EP/P03165X/1 (DG, KS, SM), EP/ M015254/2 (EWJ), EU via ERDF for SPARC II (CK), EP/ N020863/1 (JM) and the National Mass Spectrometry Facility at Swansea University. We also acknowledge EPSRC funding for the National Crystallography Centre at Southampton University, and Swansea University College of Engineering AIM Facility, which was funded by EPSRC (EP/M028267/1) and the European Regional Development Fund (80708). We acknowledge use of Hartree Center resources in this work. The Science and Technology Facilities Council (STFC) Hartree Center is a research collaborator in association with IBM providing High Performance Computing platforms funded by the U.K.'s investment in e-Infrastructure. The Center aims to develop and demonstrate next generation software, optimized to take advantage of the move toward exa-scale computing.

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