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Charge recombination in polythiophene: non-fullerene acceptor solar cells with IE offsets exceeding 1 eV

In organic solar cells the energetic landscape of the donor–acceptor heterojunction determines the efficiency of charge generation and charge recombination processes, and thereby the device performance. Here, we present a study on a series of 15 donor–acceptor bulk heterojunctions (BHJs) consisting of either the donor polymer poly(3-hexylthiophene) (P3HT) or poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (pBTTT-C14) and selected non-fullerene acceptors (NFAs), spanning a wide range of interfacial energetics. We demonstrate that the internal quantum efficiency (IQE) is limited by geminate and non-geminate recombination processes and, importantly, decreases with the energy difference between the donor's ionization energy (IE) and the acceptor's electron affinity (EA), in other words, the diagonal bandgap, specifically if less than 1 eV, regardless of the interfacial IE offset. The dependence of charge recombination on the diagonal bandgap can be explained in the framework of the energy gap law. Our results provide further insight into the importance and impact of interfacial energetics in donor:NFA blends with large IE offsets.

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Wejdan Althobaiti, Julien Gorenflot, Catherine S. P. De Castro, Jafar I. Khan, Christopher E. Petoukhoff, Shahidul Alam, Oleksandr Matiash, Yakun He, George T. Harrison, Anirudh Sharma, Weimin Zhang, Valentina Musteata, José P. Jurado, Marco Marengo, Derya Baran, Stefaan De Wolf, Iain McCulloch, Shadi Fatayer, Frédéric Laquai

Locally Resolved Thermally Induced Degradation of PM6:Y6-Based Organic Solar Cells

The limited thermal stability of organic solar cells has hampered their commercialization. Therefore, it is crucial to gain in-depth insight into the underlying causes of thermal device instability and to develop practical approaches to reduce its impact. In this study, we examine thermal degradation processes of the donor/acceptor system PBDB-T-2F:BTP-4F (alias PM6:Y6) in bulk heterojunction polymer/nonfullerene acceptor (NFA) solar cells, considered as a state-of-the-art system of the organic photovoltaics (OPV) technology. More specifically, this study investigates the effects of varying postproduction annealing temperatures on the performance of solar cells and locally resolves the thermally induced impact on these solar cells using a set of advanced imaging techniques, including photoluminescence imaging (PLI), electroluminescence imaging (ELI), and light beam-induced current (LBIC) measurements.

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Shahidul Alam, José P. Jurado, Zhuo Xu, Aurelien D. Sokeng, Biswajit Pal, Mariia Ferree, Xinyu Jiang, Sasha Simotko, Gitti L. Frey, Ulrich S. Schubert, Peter Müller-Buschbaum, Harald Hoppe, Frédéric Laquai

Determining Exciton Diffusion Length in Organic Semiconductors: Unifying Macro- and Microscopic Perspectives

Long exciton diffusion length (LD) is key to maximizing excitation harvesting in organic solar cells, but contradicting values are reported for non-fullerene acceptors (NFA). To understand the factors enabling large LD, experimental observation of exciton decay by transient absorption spectroscopy (TAS) is combined with microscopic Kinetic Monte Carlo (KMC) simulations on 4 ITIC derivatives. Exciton decays are fitted considering singlet exciton-singlet exciton annihilation (SSA) and the intrinsic exciton's lifetime τ, resulting in LD from 20 to 70 nm. The critical importance of an independent estimate of τ is discussed and its measurements from pristine NFA films is found to be more relevant than from NFA molecules embedded in an inert polystyrene matrix. From experimental parameters, the microscopic Förster Resonant Energy Transfer hopping rate and the annihilation rate in a cubic lattice are determined, considering a Gaussian energetic disorder. KMC simulation of those rates are able to reproduce the experimental transients and LD, provided a lattice constant a close to the molecular π-π stacking distance is used. It is found that this tight packing and a low disorder are critical to reach large LD, and empirically relate linearly such that 40 meV more disorder can be compensated by 1 Angstrom tighter packing (shorter a).

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Wenchao Yang, Catherine S. Pursglove De Castro, Safakath Karuthedath, Yuliar Firdaus, Nisreen Alshehri, Si Chen, Diego Rosas Villalva, Christopher E. Petoukhoff, Amr Dahman, Derya Baran, Thomas D. Anthopoulos, Frédéric Laquai, Julien Gorenflot

We aim to understand photophysical processes in photovoltaic devices and photocatalysts to identify loss channels and improve their efficiency and stability. Read our publications or contact us directly if you want to know more.

All publications

Here you find our most recent publications. The complete list throughout the years is available in our Google Scholar overview.

Title Cited by Year
Bulk Passivation of Molybdenum Trioxide Enables Inverted Organic Photovoltaics with Significantly Enhanced Stability under Extreme Conditions Qianqian Qi, Jiaming Huang, Cenqi Yan, Jiayu Wang, Jiehao Fu, …, Pei Cheng Advanced Materials 38 (15), e22299 9 2026
One-Step Formation of 2D/3D Perovskite Heterojunction via Ligand Intercalation and Facet Engineering for Efficient Perovskite Solar Cells Drajad Satrio Utomo, Yanping Liu, Andi Muhammad Risqi, Mohammed Ghadiyali, Imil Fadli Imran, …, Stefaan De Wolf Nano-Micro Letters 18 (1), 240 7 2026
Self-Assembly Control of Y-Series Non-fullerene Acceptors for Sustainable and Scalable Organic Photovoltaics Dingqin Hu, Hua Tang, Jiehao Fu, Yaohui Li, Lei Liu, …, Hsu Hsien-Yi Nano-Micro Letters 18 (1), 182 6 2026
Short-Wavelength Infrared Imaging with Organic Photodetectors Based on Non-Fullerene Acceptors with Detection above 1200 nm Zhuoran Qiao, Sandeep Sharma, Yakun He, Marie Houot, K-Y Lin, …, Nicola Gasparini Advanced Materials 38 (31), e22600 5 2026
Tailoring polymers of intrinsic microporosity as photoredox catalysts for continuous-flow reaction–separation processes Martin Gede, Gergő Ignácz, Catherine S. P. De Castro, Büşra Dereli, Mariia V. Ferree, …, György Székely Nature Communications 17 (1) 3 2026
Charge recombination in polythiophene: non-fullerene acceptor solar cells with IE offsets exceeding 1 eV Wejdan Althobaiti, Julien Gorenflot, Catherine S. P. De Castro, Jafar Iqbal Khan, Christopher E. Petoukhoff, …, Frédéric Laquai Energy & Environmental Science 19 (2), 659–679 2 2026
Locally Resolved Thermally Induced Degradation of PM6:Y6-Based Organic Solar Cells Shahidul Alam, Jose Piers Jurado, Zhuo Xu, Aurelien Sokeng Djoumessi, Biswajit Pal, …, Frédéric Laquai ACS Applied Energy Materials 9 (3), 1669–1679 2 2026
Ink-state preaggregation control enables scalable and automated fabrication of highly efficient and stable organic photovoltaics Hua Tang, Dingqin Hu, Rong Wang, Yaohui Li, Peihao Huang, …, Christoph Josef Brabec Science Advances 12 (9), eaea6522 2 2026
Synthetic Surface Design of Transparent Electrodes for Enhanced Molecular Contact in Perovskite Solar Cells Rik Hooijer, Sunwoo Kim, Sebastian Klenk, Hao Zhu, Cem Yilmaz, …, Erkan Aydın Advanced Energy Materials 16 (26) 1 2026
Photophysics and Device Performance of a Pyran-Bridged Pentacyclic A-D-A-Type Non-Fullerene Acceptor (NFA) in Organic Solar Cells Wejdan Althobaiti, Yakun He, Sandeep Sharma, Julien Gorenflot, Wisnu Tantyo Hadmojo, …, Frédéric Laquai Advanced Optical Materials 14 (17) 1 2026

This list is updated automatically (source: OpenAlex, via ORCID iD). Citation counts may differ slightly from Google Scholar.

Google Scholar overview

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