SKM 2023 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 11: Focus: Organic Solar Cells Based on Non-fullerene Acceptors: Loss Mechanism and Options for Above 20 % Efficiencies II

CPP 11.6: Talk

Monday, March 27, 2023, 16:45–17:00, GÖR 226

Charge transfer and structural control in block co-polymer OPVs — •Jolanda Müller, Flurin Eisner, Jun Yan, Jie Min, and Jenny Nelson — Blackett Laboratory, Imperial College London, South Kensington, SW7 2AZ, UK

The efficiencies of organic photovoltaics (OPVs) have seen a sharp increase in recent years thanks to the development of new non-fullerene acceptors. However, achieving long-term performance stability in the higher efficiency OPVs is still challenging, in particular due to de-mixing of components in bulk-heterojunction when exposed to light and heat. A promising approach to tackle this stability issue is the use of single-component macromolecular semiconductors (Review by Roncali, 2021), which have recently showed significant improvements in conversion efficiency reaching >11% in a block co-polymer system while maintaining good performance stability (Wu et al., 2021b).

Here, by combining state-of-the art polymer donors and non-fullerene acceptors into block co-polymers we gain a deeper physical understanding of charge generation and transport in block co-polymer systems based on PBDB-T and PY-T material groups. Firstly, we use chemical modifications to the building blocks of the polymers to tune the energetics in the system to understand the interplay between through-space and through-bond charge transfer. Secondly, we modify the large-scale structure of the polymers by tuning the length of the donor and acceptor segments to make a comparison to a traditional polymer-polymer bulk-heterojunction. These new material systems are analysed using optoelectronic measurements and device and molecular-scale modelling to better understand the morphological ordering in block co-polymers and the impact the morphology has on the device properties. Combining the advances in efficiency thanks to novel chemical design of donors and acceptors with the long-term stability of the block co-polymer structure will hopefully lead to industrially viable organic solar cells