Magical Interfacial Engineering! HKUST(GZ) Professor Jiaying WU's Team Publishes Key Findings in Top 'Nature' Journal, Unraveling Voltage Loss in Organic Solar Cells
Researchers led by Assistant Professor Jiaying WU from the Advanced Materials Thrust of the Function Hub at The Hong Kong University of Science and Technology (Guangzhou) recently published their latest findings in a Nature family journal.
Their work proposes a new strategy for reducing non-radiative recombination in organic solar cells (OSCs), offering fresh insights into mitigating voltage losses in these devices. The research results were published in Nature Communications (2025 impact factor: 15.7), with HKUST(GZ) serving as the first institutional affiliation.
Paper title
Suppressing Electron-Phonon Coupling and Energy Loss in Organic Solar Cells by Modulating Donor-Acceptor Penetrated-Interface
Author information
Yongmin LUO, Yulong HAI, and Yao LI from Professor Jiaying WU's group at HKUST(GZ) contributed equally as co-first authors, and Professor Jiaying WU serves as the sole corresponding author.
DOI
https://www.nature.com/articles/s41467-026-68731-7
Acknowledgement:
This work was supported by the National Natural Science Foundation of China (Young Scientists Fund, Category C). The authors gratefully acknowledge the technical support provided by the Green e-Materials Laboratory (GeM) at HKUST(GZ), the Materials Characterization and Preparation Facility at HKUST(GZ) (MCPF-GZ), and the Materials Characterization and Preparation Facility at HKUST (MCPF).
Research overview
Organic solar cells (OSCs) have achieved power conversion efficiencies exceeding 20 percent in recent years. However, further improvements remain constrained by non-radiative energy loss (qΔVnr), which limits the attainable open-circuit voltage (VOC). Previous studies have shown that non-radiative losses are primarily governed by charge-transfer (CT) states at donor–acceptor interfaces. The three-state model, which incorporates the hybridization between localized exciton states and CT states, provides a theoretical framework to explain how systems with small energetic offsets can still maintain high VOC.
Nevertheless, the formation and decay of interfacial CT states are determined not only by the electronic energy level alignment but also by the microscopic interfacial structure.
Meanwhile, electron–phonon coupling (EPC) has been recognized as a fundamental physical origin of non-radiative recombination. However, most existing studies have focused on neat materials or isolated molecular configurations, while systematic investigations of EPC in complex donor–acceptor interfaces remain limited.
In particular, for the rapidly developing all-polymer solar cells, their unique phase separation and interfacial mixing characteristics may alter EPC behavior. Whether such changes affect charge generation and voltage loss, and how these effects manifest, remain open questions. In this work, we investigate a series of representative polymer donor–small molecule acceptor systems (PD–SMA) as well as all-polymer systems (PD–PA). By tuning the donor–acceptor composition ratio, we systematically examine the evolution of interfacial morphology, charge-transfer state dynamics, and electron–phonon coupling characteristics. This study aims to elucidate the intrinsic relationship between interfacial structure, EPC, and non-radiative energy loss.
Research results
Spectroscopic, electrochemical, and energy-level analyses first revealed that during variations in the donor–acceptor composition ratio, polymer acceptor (PA) systems exhibit a more gradual evolution of energy levels and lower energetic disorder compared with small-molecule acceptor (SMA) systems.
Further structural characterization using grazing-incidence wide-angle X-ray scattering (GIWAXS) and grazing-incidence small-angle X-ray scattering (GISAXS) revealed fundamentally different interfacial evolution pathways between the two systems.
In SMA systems, rapid phase separation tends to occur, forming highly crystalline pure phases with interfaces dominated by highly disordered mixed regions. In contrast, PA systems undergo a progressive structural evolution: starting from a fully disordered mixed state, then forming an intermediate interfacial structure composed of quasi-aggregated acceptor domains penetrated by donor chain segments, and finally evolving into crystalline pure phases.
Based on these observations, the authors proposed and defined two distinct types of donor–acceptor interfacial structures:
(1) an Entangled-interface (E-interface), characterized by a completely disordered and highly intertwined donor–acceptor configuration, and
(2) a Penetrated-interface (P-interface), composed of quasi-aggregated acceptor clusters penetrated by donor polymer chains.
Theoretical calculations indicate that the E-interface corresponds to a relatively parallel stacking configuration between donor and acceptor molecules, whereas the P-interface favors a cross-stacking configuration.
The latter exhibits significantly lower internal and external reorganization energies, thereby substantially weakening electron–phonon coupling (EPC).
Transient absorption spectroscopy and pump–push–probe measurements further demonstrate that charge generation can proceed through both E-interface and P-interface pathways. However, the P-interface is more favorable for exciton dissociation and rapid separation of CT states, significantly reducing the accumulation of bound CT excitons.
By combining the three-state model with Marcus–Levich–Jortner theoretical analysis, the authors quantitatively demonstrate that the reduction of EPC is the dominant factor responsible for the significant suppression of non-radiative energy loss.
In PA systems, where the fraction of P-interfaces is higher, the non-radiative voltage loss (qΔVnr) is reduced by approximately 55–60 meV compared with SMA systems.
Furthermore, by introducing polymer acceptors into SMA systems to construct ternary blends, the authors experimentally confirmed that increasing the proportion of P-interfaces provides a viable strategy for enhancing the open-circuit voltage (VOC).
Research significance
This study provides a clear and unified physical picture of non-radiative energy loss in organic solar cells from the perspective of interfacial structure.
Our results demonstrate that donor–acceptor interfaces should not be viewed as a single disordered region, but rather as a combination of multiple interfacial configurations with distinct electron–phonon coupling (EPC) characteristics.
Among them, the penetrated interface (P-interface), which intrinsically exhibits weaker EPC due to reduced reorganization energies, emerges as a key structural motif for achieving low voltage loss.
Importantly, the study reveals that the commonly observed low non-radiative voltage loss (qΔVnr) in all-polymer solar cells does not arise solely from favorable energy-level alignment or exciton delocalization effects. Instead, it is closely associated with their interfacial morphology, which more readily forms a higher proportion of P-interfaces. This finding provides a direct structural explanation for why all-polymer systems can maintain high open-circuit voltages even under small energetic offsets.
From a device design perspective, this work introduces a new strategy for minimizing voltage loss through the regulation of interfacial electron–phonon coupling. The results offer important guidelines for future material design, ternary blend engineering, and interface optimization, and provide broadly applicable design principles for overcoming the efficiency limitations of organic solar cells.
About the authors
Yongmin LUO is a third-year PhD candidate in the Advanced Materials Thrust, Function Hub, at The Hong Kong University of Science and Technology (Guangzhou). His research focuses on ultrafast spectroscopic techniques, including transient absorption spectroscopy (TAS), pump–push–probe spectroscopy (PPP), femtosecond stimulated Raman spectroscopy (FSRS), and femtosecond time-resolved photoluminescence (fs-TRPL) based on upconversion methods. He also has extensive experience with X-ray–based characterization techniques such as grazing-incidence wide-angle X-ray scattering (GIWAXS) and grazing-incidence small-angle X-ray scattering (GISAXS). His current research investigates carrier dynamics at donor–acceptor interfaces in organic semiconductors. He has published his work as either the first author or co–first author in leading journals including Nature Communications, Nature Materials, Energy & Environmental Science (3 papers), Advanced Materials (2 papers), and Advanced Energy Materials (3 papers). As of January 2026, his h-index is 14.
Yulong HAI received his PhD from the Advanced Materials Thrust at The Hong Kong University of Science and Technology (Guangzhou) under the supervision of Professor Jiaying WU. His research focuses on the theoretical study of electronic structure, carrier dynamics, and electron–phonon coupling in organic molecular systems, with publications in Energy & Environmental Science, Nature Communications, and Advanced Materials.
Yao LI received her PhD in 2025 from the Advanced Materials Thrust at The Hong Kong University of Science and Technology (Guangzhou). Her research focuses on device physics and charge carrier dynamics in optoelectronic devices, with particular emphasis on organic photovoltaics (OPVs) and organic photodetectors (OPDs). She has extensive experience in ultrafast spectroscopic techniques, including transient absorption spectroscopy (TAS), transient photovoltage/photocurrent (TPV/TPC), and pump–push–probe transient absorption spectroscopy (PPP). Her work aims to elucidate the microscopic mechanisms governing device operation and enhance device efficiency and long-term stability through kinetic control.
Jiaying WU is an Assistant Professor in the Advanced Materials Thrust, Function Hub, at The Hong Kong University of Science and Technology (Guangzhou), and a joint Assistant Professor in the Department of Chemical and Biomolecular Engineering at The Hong Kong University of Science and Technology. She received her PhD from Imperial College London under the supervision of Professor James R. Durrant FRS and earned her BEng from the University of Electronic Science and Technology of China. Her research focuses on the photo-physics and charge carrier dynamics of emerging materials for solar energy conversion, with applications in photovoltaics, photodetectors, and photocatalysis. Her current work aims to advance the understanding of photophysical and optoelectronic processes in photon-energy conversion materials and devices using ultrafast spectroscopy and transient optoelectronic characterization techniques. At HKUST(GZ), she leads the Ultrafast Photophysics Research Group, specializing in advanced ultrafast spectroscopic characterization to address the core scientific challenges of next-generation optoelectronic materials and technologies. She has published over 100 peer-reviewed articles in leading journals including Science, Energy & Environmental Science, Nature Communications, Joule, and Advanced Materials, with more than 4,400 citations and an h-index of 33 as of January 2026.
The Ultrafast Photophysics Research Group at HKUST(GZ) is seeking motivated master's and PhD students, research assistants, and postdoctoral researchers to explore fundamental photophysical mechanisms in optoelectronic materials and devices. For more information about the PI's research and for contact details, please refer to:
https://facultyprofiles.hkust-gz.edu.cn/faculty-personal-page/WU-Jiaying/jiayingwu
