Materials for energy harvesting are pivotal to global decarbonisation efforts and the prevention of climate breakdown [1]. This workshop will focus on photovoltaic and thermoelectric materials, which generate electricity from solar energy and waste heat, respectively. While both technologies are relatively mature and commercially available [2,3], their adoption and the breadth of their applications could increase significantly if the efficiency of their energy conversion processes were substantially improved. 

Achieving such improvements requires a deeper understanding of the fundamental interactions that govern material properties — including electron-phonon and electron-electron interactions, as well as interactions with defects and external perturbations such as light. Recent advances in modelling techniques, advanced simulation techniques, and machine-learning–driven workflows have enabled unprecedented insight into these processes [4,5]. The workshop will bring together leading experts in these areas to discuss recent breakthroughs and identify new directions for dramatically enhancing the performance of thermoelectric and photovoltaic materials. 

Photovoltaic and thermoelectric technologies often rely on similar classes of materials, including inorganic bulk compounds and their nanostructured forms, and more recently, two-dimensional, organic, and hybrid materials [2,3]. In photovoltaics, the operation is typically governed by electron-phonon, electron-electron, and electron-defect interactions, alongside coupling with photons. In thermoelectrics, phonon-phonon and electron-phonon interactions are considered central, together with phonon-defect and electron-defect interactions. Therefore, electron-phonon and electron-defect interactions are of significant interest to both communities.  

However, emerging research has revealed a deeper set of commonalities between photovoltaics and thermoelectrics. For instance, electron-electron interactions play a crucial role in accurately modelling electron-phonon interactions in narrow-bandgap and intermetallic thermoelectric materials [6,7]. In halide perovskites, strong phonon-phonon interactions can significantly influence photovoltaic performance [8]. Similarly, plasmons, typically employed to enhance solar absorption in metallic nanostructures [9], may also benefit thermoelectric materials with high doping levels. Finally, polarons — quasiparticles formed by electrons interacting strongly with lattice vibrations — are increasingly recognized as relevant to both fields, particularly in oxides, organic and two-dimensional materials [10]. 

Recent years have seen major progress in first-principles methods capable of capturing these complex interactions [4-14]. Beyond well-established Boltzmann transport approaches for electron and phonon transport, new techniques are being developed to describe coupled electron-phonon and electron-phonon-photon dynamics [15,16], opening new paradigms for designing materials with enhanced conversion efficiencies. Parallel efforts are translating some of these advances into high-throughput, machine learning–assisted workflows, accelerating the discovery of materials with improved figures of merit [17-18].

This workshop will highlight recent advances in theoretical and computational methods used to characterize the interactions and dynamics in realistic materials and their implications on thermoelectric and solar energy conversion. Several invited talks will also explore the application of modern AI and machine learning techniques for the discovery of novel photovoltaic and thermoelectric materials. Approximately half of the invited presentations will focus on experimental research, including the synthesis of new materials and the characterization of key interaction mechanisms. Together, these contributions aim to identify the most pressing challenges in designing next-generation materials with significantly improved energy conversion efficiencies.