Robert Hoye

Our vision is to develop a new generation of energy materials that can tolerate defects to achieve efficient performance when grown by cost-effective, scalable synthetic approaches. We are an interdisciplinary team, with interests spanning from creating new fundamental insights into carrier-matter interactions, through to applying this understanding to develop high-performing devices for clean energy conversion. Our research is experimentally focussed, but we have strong collaborations with theory groups.

Perovskite-Inspired Materials

Defects are ubiquitous in materials, and, historically, efforts at mitigating their deleterious effects have focussed on expensive, high-temperature methods to minimise defect densities. The more recent development of lead-halide perovskites in photovoltaics has brought to the fore the concept of ‘defect-tolerance’, in which efficient performance can still be achieved despite high defect densities being present. Our focus is on developing broader classes of materials that can mimic this defect tolerance, especially in sustainable materials with nontoxic elements. These have included bismuth-based perovskites, chalcohalides and chalcogenides.

We study the interplay between crystal and electronic structure, and the effects of defects and carrier-phonon interactions on charge-carrier transport in these materials, utilising a range of advanced techniques, including ultrafast spectroscopy, photoemission spectroscopy and atom probe tomography.

• Strong Absorption and Ultrafast Localisation in NaBiS₂ Nanocrystals with Slow Charge-Carrier Recombination [Nature Communications, 2022] 
• The Defect Challenge of Wide-Bandgap Semiconductors for Photovoltaics and Beyond [Nature Communications, 2022]
• Strongly Enhanced Photovoltaic Performance and Defect Physics of Air-Stable Bismuth Oxyiodide (BiOI) [Advanced Materials, 2017]

Optoelectronic Materials Development

We have devised a range of solution- and vapour-based methods for synthesising high-quality nanocrystals, thin films and single crystals of novel materials. These include chemical vapour transport, spatial atomic layer deposition, and ligand-assisted reprecipitation of nanoplatelets with controlled thickness. We focus on scalable and sustainable synthetic approaches, as well as gaining insights into the mechanistic steps involved (e.g., influence of antisolvent polarity on nanocrystal surface chemistry). 

•    Elucidating the Role of Antisolvents on the Surface Chemistry and Optoelectronic Properties of CsPbBr_xI_3-x [JACS, 2022]
•    Rapid Vapor-Phase Deposition of High-Mobility p-Type Buffer Layers on Perovskite Photovoltaics for Efficient Semitransparent Devices [ACS Energy Letters, 2020]

Deriving Functionality from New Materials

Through careful control over bulk properties and interfaces, we have assembled complex structures to derive functionality from new materials, with applications spanning from photovoltaics, photoelectrochemical cells, light-emitting diodes and radiation detectors. 

•    Long-Term Solar Water and CO₂ Splitting with Photoelectrochemical BiOI-BiVO₄ Tandems [Nature Materials, 2022]
•    Pressing Challenges in Halide Perovskite Photovoltaics – From the Atomic to Module Level [Joule, 2021]