Pnictogen-based semiconductors for Harvesting EneRgy from Ambient Light to power autonomous Devices (HERALD)
Lead Research Organisation:
University of Oxford
Department Name: Oxford Chemistry
Abstract
HERALD aims to instigate a step-change in how smart devices are powered by developing new classes of pnictogen-based semiconductors to more efficiently collect the widely-available energy from lighting inside buildings. Such energy can be renewably harvested with indoor photovoltaics (IPV), which is highly appealing for powering the billions of autonomous smart devices driving the fourth industrial revolution. However, industry-standard IPV (hydrogenated amorphous silicon; a-Si:H) have efficiencies up to only ~20%, with most commercial devices <10% efficient.
HERALD will develop IPV from novel classes of rudorffites and chalcohalides, which have potential to reach >48% efficiency under indoor lighting. These are low-toxicity, high-stability materials based on the pnictogens bismuth and antimony, and their considerable potential for indoor light harvesting is just starting to emerge. HERALD will transform these novel compounds into leading IPV using a hierarchical characterisation approach, from the macro- to near-atomic-scale. Along the way, fundamental understanding will be gained to learn what the performance-limiting factors are and how they can be systematically mitigated. The endpoint will be high-performing, durable test devices with low environmental impact. The materials will be rapidly grown at scale using a novel plasma-spray technique, and the IPV prototyped in commercial smart devices.
The pnictogen-based IPV developed can have a transformative impact on smart devices by decreasing their reliance on being powered only by batteries, which need to be regularly replaced, creating significant waste. The new IPV can be deployed without harming the environment and will harvest more power than a-Si:H IPV to sustain smart devices with more advanced capabilities. The pioneering development of pnictogen-based semiconductors will also push them forward for numerous PV, from clean solar fuel production to radiation detection for medical imaging.
HERALD will develop IPV from novel classes of rudorffites and chalcohalides, which have potential to reach >48% efficiency under indoor lighting. These are low-toxicity, high-stability materials based on the pnictogens bismuth and antimony, and their considerable potential for indoor light harvesting is just starting to emerge. HERALD will transform these novel compounds into leading IPV using a hierarchical characterisation approach, from the macro- to near-atomic-scale. Along the way, fundamental understanding will be gained to learn what the performance-limiting factors are and how they can be systematically mitigated. The endpoint will be high-performing, durable test devices with low environmental impact. The materials will be rapidly grown at scale using a novel plasma-spray technique, and the IPV prototyped in commercial smart devices.
The pnictogen-based IPV developed can have a transformative impact on smart devices by decreasing their reliance on being powered only by batteries, which need to be regularly replaced, creating significant waste. The new IPV can be deployed without harming the environment and will harvest more power than a-Si:H IPV to sustain smart devices with more advanced capabilities. The pioneering development of pnictogen-based semiconductors will also push them forward for numerous PV, from clean solar fuel production to radiation detection for medical imaging.
Publications
Blakesley J
(2024)
Roadmap on established and emerging photovoltaics for sustainable energy conversion
in Journal of Physics: Energy
Chen X
(2024)
Additive engineering for Sb2S3 indoor photovoltaics with efficiency exceeding 17.
in Light, science & applications
Dudipala KR
(2024)
Halide Perovskites and Their Derivatives for Efficient, High-Resolution Direct Radiation Detection: Design Strategies and Applications.
in Advanced materials (Deerfield Beach, Fla.)
Fu Y
(2025)
Structural and electronic features enabling delocalized charge-carriers in CuSbSe2
in Nature Communications
Grandhi G
(2023)
Wide-Bandgap Perovskite-Inspired Materials: Defect-Driven Challenges for High-Performance Optoelectronics
in Advanced Functional Materials
Guo X
(2023)
Air-stable bismuth sulfobromide (BiSBr) visible-light absorbers: optoelectronic properties and potential for energy harvesting
in Journal of Materials Chemistry A
Liu S
(2024)
Data-Driven Controlled Synthesis of Oriented Quasi-Spherical CsPbBr 3 Perovskite Materials
in Angewandte Chemie
Liu S
(2024)
Data-Driven Controlled Synthesis of Oriented Quasi-Spherical CsPbBr3 Perovskite Materials.
in Angewandte Chemie (International ed. in English)
Otero-MartÃnez C
(2024)
Organic A-Site Cations Improve the Resilience of Inorganic Lead-Halide Perovskite Nanocrystals to Surface Defect Formation
in Advanced Functional Materials
Ye J
(2024)
Strongly-confined colloidal lead-halide perovskite quantum dots: from synthesis to applications.
in Chemical Society reviews
| Description | This project has two main components: 1) development of a novel class of chalcogenides, halides and chalcohalides for indoor photovoltaics, a and 2) prototyping of these materials in indoor photovoltaic devices, and their demonstration in powering IoT electronics. For the first area, we made substantial efforts in Ag-Bi-I compounds, including the rudorffites Ag2BiI5 and AgBiI4. This efforts was led by research fellow Dr. Huimin Zhu, funded through a Iberdrola Energy for Future fellowship, which is part of the Marie Curie scheme, working alongside DPhil students Ivy Liu and Xiaoyu Guo. They found that although these materials have strong optical absorption that is well matched to the spectra of indoor light sources, it is highly challenging to achieve compact thin films of this material. Given the significant amount of experimental data we created in efforts to achieve compact morphology, we formed a new collaboration with Prof. Shijing Sun (University of Washington in Seattle, USA) on the use of neural networks (https://chemrxiv.org/engage/chemrxiv/article-details/6784b8356dde43c908499dfe). In doing so, we developed a model that confirm the experimental conditions for achieving compact morphology. But even then, the performance of these materials is low. We developed a Li-TFSI interface treatment which improved efficiencies, but still well below 10%. We suspect that charge-carrier transport in these materials is limited by the formation of excitons, and are currently working towards computations and spectroscopy measurements to determine the exciton binding energies of the Ag-Bi-I system. In addition to these research efforts, we wrote a comprehensive review on this materials system (https://doi.org/10.1177/09506608231213065). At present, we are working on finishing these remaining research efforts into the Ag-Bi-I system, which will provide a much more complete picture of the potential of these materials for photovoltaic applications. We had much more success with Sb2S3. This was made in collaboration with Prof. Ru Zhou from Hefei University of Technology. He visited us for 6 months, funded by the China Scholarship Council, working on this material system within our group, collaborating with DPhil student Yuchen Fu. Working together, we achieved Sb2S3 indoor photovoltaics with 17.6% efficiency under indoor lighting. This was by using monoethanolamine as the complexing agent, which lead to a substantial increase in grain size, lowering non-radiative recombination. We fabricated 1 cm^2 area Sb2S3 devices, and connected five of these in series to prototype them powering a multi sensor platform used for IoT (https://doi.org/10.1038/s41377-024-01620-0). These we demonstrated to be stable for the entire two week period we tested them over. As a result of these promising results, we secured a collaboration with Nissan Motor Corporation, developing Sb2S3 for top-cells in tandem photovoltaics for integration with electric vehicles. Beyond these materials, we are also working on other chalcogenide systems, and this is led by postdoc Yongjie Wang (nanocrystals) and Chia-Yu (Minette) Chang (thin films). This was spurred through a collaboration with the group of Prof. Edgardo Saucedo (UPC in Barcelona), enabled by a visit from his former PhD students Ivan Caño. This is an ongoing series of projects. We are also working on BiSBr thin film and nanocrystals. We demonstrated this novel material to hold potential for indoor photovoltaics (https://doi.org/10.1039/D3TA04491B), but is limited by its non-compact morphology. At present, we are working on understanding extrinsic self-trapping in this system. This effort is led by DPhil student Xiaoyu Guo and postdoc Dr. Jason Ye, working alongside theory collaborators at UPC in Barcelona. We aim to wrap up this work later this year. Beyond these research projects, we have engaged with the growing community in Europe working on indoor photovoltaics. Together with several colleagues, we recently published a review on emerging materials for this area in Nature Reviews Clean Technology (https://www.nature.com/articles/s44359-024-00013-1). In addition, we are a partner in a recent Marie Curie Doctoral Training Network called MASAUTO, and will have a joint PhD student with Prof. Akshay Rao (University of Cambridge) as part of this. Furthermore, we are involved in several efforts currently to standardise the measurement and reporting on indoor photovoltaics. As part of this, we secured a project funded by the Henry Royce Institute with Lightricity Ltd. to develop an indoor light simulator for testing emerging photovoltaic materials, and this commercially available. |
| Exploitation Route | The works we have already published on BiSBr, Sb2S3 and Ag-Bi-I materials advance the knowledge of these materials. In particular, the prototyping of Sb2S3 indoor photovoltaics for IoT electronics motivates the sizeable community working on this material to focus on this as a promising application, which can see commercial use. The more fundamental work on BiSBr and Ag-Bi-I are conducting right now has broad impact on wider classes of related materials, which will shape the types of materials the wider field will focus on in the future. The efforts we are engaged with right now on standardisation of indoor photovoltaic testing will be pivotal for the growth of this field, just as following standard test conditions for solar PV has been instrumental in its maturation. |
| Sectors | Education Electronics Energy |
| URL | https://doi.org/10.1038/s41377-024-01620-0 |
| Description | We worked with Lightricity Ltd in a project funded through the Henry Royce Institute to develop an indoor light simulator for emerging photovoltaic materials. This simulator is now commercially available, and can be used by the wider community for standard testing of indoor photovoltaic devices. Our current ongoing efforts to move the field towards a consensus on standard testing conditions for indoor photovoltaics will improve the reproducibility of results in the field moving forward, and ensure fair comparisons in technologies as these indoor photovoltaics become commercialised. |
| First Year Of Impact | 2024 |
| Sector | Electronics,Energy |
| Impact Types | Economic Policy & public services |
| Description | Roadmap for photovoltaics research |
| Geographic Reach | Multiple continents/international |
| Policy Influence Type | Contribution to a national consultation/review |
| Impact | This roadmap is written in an accessible way, and is available to the whole public. By providing a comprehensive discussion of the status and challenges across the breadth of the photovoltaics field, we communicated to the wider public, both within the community and in the wider energy community, the key areas to focus on for photovoltaics, and key areas requiring further investment. To make this roadmap more widely known, we spoke about it in a podcast with Physics World, which is available here: https://physicsworld.com/a/how-to-boost-the-sustainability-of-solar-cells/ |
| URL | https://doi.org/10.1088/2515-7655/ad7404 |
| Description | Tutorials on photovoltaic materials and ultrafast spectroscopy |
| Geographic Reach | National |
| Policy Influence Type | Influenced training of practitioners or researchers |
| Impact | These courses provide a strong foundation in the fundamentals of photovoltaics and spectroscopy, upon which our research is based. Following the delivery of these courses, there was an improved level of understanding, as evidenced in the ability of the students to engage with the concepts, and ability to analyse the data obtained. The improved skills of the wider cohort of students taught from the IMAT CDT was evidenced from the work they produced in the workshops. |
| Description | Henry Royce Institute Industrial Collaboration Programme |
| Amount | £153,713 (GBP) |
| Funding ID | ICP002 (EPSRC reference no: EP/X527257/1) |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 11/2022 |
| End | 03/2023 |
| Description | John Fell Fund |
| Amount | £71,984 (GBP) |
| Funding ID | DPD00380 |
| Organisation | University of Oxford |
| Department | Department of Chemistry |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 01/2023 |
| End | 12/2023 |
| Description | Welcome Grant |
| Amount | £12,491 (GBP) |
| Organisation | University of Oxford |
| Department | St John's College Oxford |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 03/2023 |
| End | 12/2023 |
| Title | Air-stable bismuth sulfobromide (BiSBr) visible-light absorbers: optoelectronic properties and potential for energy harvesting |
| Description | The dataset includes the experimental data record as well as calculation (DFT) data |
| Type Of Material | Database/Collection of data |
| Year Produced | 2023 |
| Provided To Others? | Yes |
| Impact | This contained the experimental data behind the paper we wrote on investigating the potential of BiSBr for indoor photovoltaics (X. Guo, Y.-T. Huang, H. Lohan, J. Ye, Y. Lin, J. Lim, N. Gauriot, S. J. Zelewski, D. Darvill, H. Zhu, A. Rao, I. McCulloch, R. L. Z. Hoye,* Air-Stable Bismuth Sulfobromide (BiSBr) Visible-Light Absorbers: Optoelectronic Properties and Potential for Energy Harvesting. Journal of Materials Chemistry A, 2023, 11, 22775-22785.) In this work, we developed the synthesis of phase-pure BiSBr, and analysed the optical and electronic properties of this material, as well as its charge-carrier lifetime. We found that this material, which has had very few prior investigations into solar cells, holds promise for investigations for indoor photovoltaics that warrants further work. |
| URL | https://ora.ox.ac.uk/objects/uuid:2b1a6c66-2db9-4262-a827-9b2f6bde4f81 |
| Title | Direct Linearly Polarised Electroluminescence from Perovskite Nanoplatelet Superlattices |
| Description | All raw data and data collection details can be found in readme file included in this deposition |
| Type Of Material | Database/Collection of data |
| Year Produced | 2024 |
| Provided To Others? | Yes |
| URL | https://ora.ox.ac.uk/objects/uuid:ce61baea-6237-49c0-8b58-553b7bd46605 |
| Title | Structural and electronic features enabling delocalized charge-carriers in CuSbSe2 |
| Description | Raw data for all figures in the main text and SI of this paper |
| Type Of Material | Database/Collection of data |
| Year Produced | 2024 |
| Provided To Others? | Yes |
| URL | https://ora.ox.ac.uk/objects/uuid:0e28d5a4-dada-45f0-8fe0-4cd80c403a70 |
| Description | Collaboration on advanced characterisation of solar absorbers |
| Organisation | University of Strathclyde |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | We provided the novel materials to investigate, as well as the hypotheses. In this case, the materials are Ag-Bi-I semiconductors. We developed the route to synthesise these materials phase pure. |
| Collaborator Contribution | The group of Dr. Fabien Massabuau at the University of Strathclyde have expertise in advanced materials characterisation, namely EBIC, cathodoluminescence spectroscopy and EBSD measurements, as well as wavelength-dispersive X-ray spectrometery. These measurements have provided important information on the variations in the optoelectronic properties of our materials spatially. In addition, with Dr. Massabuau, we secured a postdoctoral fellow through the Energy for Future scheme, backed by the Marie Curie scheme. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwi30IGvqfKEAxWJXUEAHeZVCIEQFnoECB4QAQ&url=https%3A%2F%2Feuropeanenergyforfuture.com%2F&usg=AOvVaw3B6Y7_PpWZl-_3ACTe2Iaa&opi=89978449 This position is filled by Dr. Huimin Zhu, who is officially hosted at the University of Strathclyde, but is also a visitor at the University of Oxford working with Prof. Hoye. Dr. Zhu has been working in Oxford on optimising the preparation of Ag-Bi-I thin films and devices. |
| Impact | H. Zhu,* I. Turkevych,* H. Lohan, P. Liu, R. W. Martin, F. C. P. Massabuau, R. L. Z. Hoye.* Progress and applications of (Cu-)Ag-Bi-I semiconductors, and their derivatives, as next-generation lead-free materials for photovoltaics, detectors and memristors. International Materials Reviews, 2024, 69 (1), 19-62. DOI: 10.1177/09506608231213065 This is an invited review paper on Cu-Ag-Bi-I semiconductors for optoelectronic applications, and captures the current state of the area we are working on together through this collaboration. |
| Start Year | 2022 |
| Description | Collaboration on developing CZTS indoor photovoltaics |
| Organisation | Polytechnic University of Catalonia |
| Country | Spain |
| Sector | Academic/University |
| PI Contribution | We brought forward a new application space for CZTS solar absorbers. Historically, this material was used for outdoor photovoltaics. Hoye recognised the potential of this material for indoor light harvesting and hosted a visiting PhD student to work on developing a new device architecture to make these devices more suitable for applications in powering IoT. |
| Collaborator Contribution | Prof. Edgardo Saucedo's group has expertise in CZTS solar absorber fabrication, and has developed an optimised solution processing route for outdoor photovoltaics. This provided an ideal starting point for Prof. Hoye's group to begin investigating this material for indoor light harvesting. |
| Impact | Prof. Hoye has hosted a PhD student (Ivan Caño-Prades) from Prof. Saucedo's group to initiate the collaboration. |
| Start Year | 2024 |
| Description | Collaboration on terahertz spectroscopy measurements |
| Organisation | University of Warwick |
| Department | Warwick Centre for Ultrafast Spectroscopy |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Optical pump terahertz probe spectroscopy measurements are essential for us to determine whether carrier localisation takes place in the materials we are investigating. This facility is available in the Centre for Ultrafast Spectroscopy at Warwick. We provide the samples, with optimised phase purity, and provide the research hypotheses. |
| Collaborator Contribution | The facility manager in the Centre provides us with access to the facility, for a standard user fee, and provides us with training to conduct the measurements. |
| Impact | We have several ongoing projects involving this collaboration. The materials and hypotheses we are currently investigating are: 1) BiOX compounds (X = I, Br, Cl); understanding the role of Bi-X ionicity and frontier orbital energy alignment on carrier localisation. 2) Cu3SbSe3, CuSbSe2, along with the S analogs; understanding the role of structure (layered vs. 3D) on carrier localisation. This is to test the generalisability of the design rules for band-like transport we developed by investigating CuSbSe2, which we recently published in Nature Communications 3) BiSBr thin films vs. nanocrystals; understand extrinsic self-trapping in this system 4) AgBiS2 thin films and nanocrystals, with hexagonal vs. disordered rock salt structures; understanding the effect of grain size and structure on carrier localisation. The 3rd and 4th areas are the furtherest advanced, while the first area is still under development. We anticipate to close these projects this year and publish on them. |
| Start Year | 2023 |
| Description | Co-organising symposium at 2023 Spring MRS Meeting & Exhibit |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | Prof. Hoye co-organised with partners from the US and Netherlands a symposium at the 2023 Spring MRS Meeting & Exhibit (San Francisco, USA) on stable perovskite optoelectronics. This spans from fundamental investigations through to the applications of these materials in devices and strategies taken to improve stability. This is critically important for not only outdoor photovoltaics but also indoor photovoltaics. Prof. Hoye also organised the sponsorship of a prize at this symposium, supported by Oxford Photovoltaics. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.mrs.org/meetings-events/spring-meetings-exhibits/past-spring-meetings/2023-mrs-spring-me... |
| Description | Talk at London International Science Youth Forum |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Schools |
| Results and Impact | I was invited to give a specialists talk on photovoltaics at the London International Science Youth Forum. This is a prestigious STEM outreach event that takes place each year, located at Imperial College London. I spoke about my research on developing novel materials for indoor light harvesting, as part of this project, and this inspired students to think more broadly about the exciting opportunities of photovoltaics. |
| Year(s) Of Engagement Activity | 2023 |
| Description | Talk at STEM Ambassador's event hosted by Royal Academy of Engineering |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | The Royal Academy of Engineering organises workshops to train their STEM Ambassadors to engage with their outreach mission to raise the profile of engineering nationally. I delivered a talk to inspire them and share my experience as a STEM Ambassador. |
| Year(s) Of Engagement Activity | 2023 |
| Description | Visit to Eton College |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Schools |
| Results and Impact | Hoye was invited to give an outreach talk to the scientific society of Eton College. He discussed with them his research into sustainable materials and future technologies for green energy harvesting for producing clean electricity or fuels. |
| Year(s) Of Engagement Activity | 2022 |