Paul Siffert Award

Defect tolerant semiconductors for energy, solar fuels and healthcare

Prof. Robert Hoye
Associate Professor, Inorganic Chemistry Laboratory
University of Oxford, UK

CTO, NanoPrint Innovations Ltd, Cambridge, UK

Optoelectronic materials underpin a wide range of applications in energy (e.g., photovoltaics), solar fuels (e.g., photoelectrochemical CO₂ reduction), healthcare (e.g., radiation detection for medical imaging) and photonics (e.g., light emitters for optical communication). There have long been ambitions to develop optoelectronic materials that give high performance but are cost-effective to manufacture. Historically, these efforts have been driven by trial-and-error, screening through materials based on optical properties, but, in many cases, encountering bottlenecks from their limited charge-carrier transport properties.

Over the past 10 years, we have worked on an alternative approach, based on the inverse design of optoelectronic materials with focus on defect tolerance, where low rates of non-radiative recombination are achieved despite high concentrations of traps. This talk discusses the evolution in understanding of how defect tolerance arises by studying lead-halide perovskites, and successes and challenges in developing lead-free, stable alternative materials that mimic this property [1]. In particular, I will discuss challenges arising from carrier localisation, and our work uncovering chemical design principles for how this limitation could be overcome [2]. Next, I will discuss promising materials that have come from this effort, such as BiOI and CuBiSCl₂, and their impact in solar cell, solar fuel, indoor photovoltaic and X-ray detector applications [3-5]. Finally, I will discuss future directions; particularly, in this age of AI and self-driving labs, I emphasise the importance of fundamental materials science to bring out design principles underpinning defect tolerance to enable targeted and efficient inverse design.

[1] Mosquera-Loi, …, Walsh,* Hoye,* Nat. Rev. Chem., 9, 287–304 (2025)

[2] Fu, Lohan, …, Hoye,* Nat. Commun., 16, 65 (2025)

[3] Hoye,* et al., Adv. Mater., 29, 1702176 (2017)

[4] Andrei, Jagt, …, Hoye,* Reisner,* Nat. Mater., 21, 864–868 (2022)

[5] Jagt, …, Hoye,* Nat. Commun., 14, 2452 (2023)

Biography:

Robert Hoye is an Associate Professor of Materials Chemistry at the University of Oxford, where he is also a Fellow of St. John’s College, and an STFC / Royal Academy of Engineering Senior Research Fellow. He completed his education at the University of Auckland, University of Cambridge, and MIT. He was a research fellow at the University of Cambridge, then Lecturer at Imperial College London, before moving to Oxford as Associate Professor.

His team focusses on developing inorganic semiconductors for energy applications, including metal-halide perovskite nanocrystals, and lead-free ns² semiconductors. His group’s research spans from fundamentals (including ultrafast spectroscopy and computations) through to optoelectronic device engineering. More information: hoyegroup.web.ox.ac.uk

Prof. Hoye has made pioneering contributions to the development of new classes of solar absorbers for efficient, cost-effective photovoltaics, particularly pushing forward the understanding of defect tolerance and electron-phonon coupling in these materials, and he has patented these novel classes of materials. His work has been recognised with awards from the Royal Academy of Engineering, Institute of Materials, Minerals and Mining (IOM3), Royal Society of Chemistry, Springer Nature (2024 Rising Star of Light), and many others from across the world. He also received the 2021 Imperial President’s Award for Outstanding Early Career Researcher.

Alongside his academic career, he is CTO of a startup (NanoPrint Innovations Ltd) commercialising the spatial atomic layer deposition (SALD) reactor he contributed to developing. SALD manufactures oxide semiconductors with comparable properties to ALD, but orders of magnitude faster and without vacuum. For his success in commercialisation, he was included in the 2023 MIT Technology Review Innovators Under 35 Europe.