Luminescent Waveguide Encoded Lattices (LWELs) for Indoor Photovoltaics
Lead Research Organisation:
University of Cambridge
Department Name: Materials Science & Metallurgy
Abstract
The Internet of Things (IoT) underpins our future smart world where various electronic devices could be integrated with, and controlled by, wireless communication. Many of these devices will be standalone or portable, creating an urgent demand for off-grid power sources. Photovoltaic (PV) cells have significant potential for the purpose of recycling indoor artificial light to power the wireless electronics that form the basis of the IoT. However, there are currently two obstacles facing the use of conventional crystalline Silicon solar cells in this application: (i) they are optimised to work with sunlight, whose spectral output is very different to artificial indoor lighting and (ii) they perform poorly in diffuse, low intensity light that is typical of indoor lighting.
Here we present a new concept for indoor-light harvesting based on luminescent waveguide encoded lattices (LWELS). These are intricate photonic devices containing embedded lumophores within a planar polymer film that contains multiple waveguide channels. The LWEL is placed on the surface of a finished solar cell, where its roles to (i) convert incident light into energies that a better matched to the solar cell, (ii) provide a wide field of view to capture as much light as possible and (iii) work efficiently in diffuse light. The aim of this project is to understand the fundamental structure-property function relationships that underpin the design of an efficient LWEL. This includes designing and making LWELs with different waveguide patterns, modelling and measuring the light transport pathways within the device and testing the performance under indoor lighting when integrated with solar cells. Our ultimate goal through understanding these relationships is to demonstrate a functional LWEL prototype that enhances the performance of silicon solar cells under diffuse artificial lighting. Our hope is that this will unleash the potential of silicon solar cells for indoor photovoltaics and unlock exciting new research and commercial opportunities for applications in the IoT.
Here we present a new concept for indoor-light harvesting based on luminescent waveguide encoded lattices (LWELS). These are intricate photonic devices containing embedded lumophores within a planar polymer film that contains multiple waveguide channels. The LWEL is placed on the surface of a finished solar cell, where its roles to (i) convert incident light into energies that a better matched to the solar cell, (ii) provide a wide field of view to capture as much light as possible and (iii) work efficiently in diffuse light. The aim of this project is to understand the fundamental structure-property function relationships that underpin the design of an efficient LWEL. This includes designing and making LWELs with different waveguide patterns, modelling and measuring the light transport pathways within the device and testing the performance under indoor lighting when integrated with solar cells. Our ultimate goal through understanding these relationships is to demonstrate a functional LWEL prototype that enhances the performance of silicon solar cells under diffuse artificial lighting. Our hope is that this will unleash the potential of silicon solar cells for indoor photovoltaics and unlock exciting new research and commercial opportunities for applications in the IoT.
Publications
Tunstall-GarcÃa H
(2024)
Interplay of Luminophores and Photoinitiators during Synthesis of Bulk and Patterned Luminescent Photopolymer Blends.
in ACS applied polymer materials
Zhang B
(2022)
Förster Resonance Energy Transfer in Luminescent Solar Concentrators.
in Advanced science (Weinheim, Baden-Wurttemberg, Germany)
| Description | This award has enabled the initiation of a brand-new collaboration between Prof. Rachel Evans (Cambridge, UK) and Prof. Kalaichelvi Saravanamuttu (McMaster, Canada), who have complementary expertise in the fields of luminescent solar device and waveguide encoded lattices, respectively. This unique partnership has allowed us to demonstrate proof-of-concept luminescent waveguide-encoded lattices (LWELs) for the first time. LWELs are innovative photonic materials that enable the collection, transport, and spectral conversion of diffuse light, which can be integrated with photovoltaic (PV) devices to boost their performance under indoor lighting conditions. Notably, our first-generation LWEL-PV devices show a 6% increase in current compared to the naked PV cell at large collection angles, indicating that the LWEL structure is highly effective at capturing diffuse background light. This award has also uncovered an interaction between the photoinitiator used to start the polymerisation of liquid precursors into solid LWELs and the luminophore that enables the spectral conversion of diffuse indoor light. We were able to identify an electron transfer as the nature of this electron interaction, which had an unprecedented effect on the formation of LWELs (publication in review - https://doi.org/10.26434/chemrxiv-2024-s6n9r-v2). Our findings translate more broadly to 3D printing of luminescent structures, where fabrication parameters would need to be adjusted for effective photocuring. Moreover, we developed a new process to remove residual photoinitiator following LWEL formation. The residual photoinitiator is a parasitic absorber of light for indoor light harvesting, which can be removed by selective bleaching of the photoinitiator over the luminophore. The award has facilitated the highly effective transfer of knowledge between the Cambridge and MacMaster groups, with the physical secondment of members of the research team in both directions enabling the assembly of the new WEL fabrication and characterisation equipment in the first 6 months of the project. This has led to increased research capability in the Cambridge lab, not only for the postdoctoral researcher directly employed on the project but also for wider members of the research team. We demonstrate that waveguide channel formation can be retained in methacrylate-siloxane and epoxy polymer blends, providing the ability to tune mechanical properties. Forming flexible and tough LWELs is particularly important for translating LWELs into robust commercial technology. We have found that the refractive index contrast between the waveguide channels in LWELs and their surroundings in polymer blends of methacrylate-siloxane and epoxy polymer blends does not arise from the phase separation of these two components. Rather, the refractive index contrast, which is critical for the ability of LWELs to guide light, arises from the different extents of polymerisation in the waveguide channels versus their surroundings. Effective teamwork has allowed the project objectives to be delivered at a pace. To protect the intellectual property surrounding this brand-new technology, we have filed invention disclosures with Cambridge Enterprise (reference 11208) and McMaster Industry Liaison Office (reference 22-087) in April 2022. Following these disclosures, we filed a provisional US patent in June 2023 (reference 63472150), with new commercial leads identified for use-case testing. |
| Exploitation Route | While first-generation LWELs are highly promising, this is an emerging research area. As such, the preliminary findings of this project will stimulate new academic research, for example, to identify new polymer blends that enable LWEL formation or to identify specific LWEL architectures that allow for further improved light capture and conversion. The prototype LWEL-PV devices may now be tested as standalone power sources for small devices, such as temperature sensors, that can be connected to the Internet of Things (IoT), which is of direct interest to multiple industrial and technological sectors, from environment monitoring in factories to healthcare. We have already started these discussions with IoT industry players and are developing further research plans based on industrial use cases. |
| Sectors | Digital/Communication/Information Technologies (including Software) Electronics Energy Environment Manufacturing including Industrial Biotechology Pharmaceuticals and Medical Biotechnology Retail Transport |
| Description | This award has started discussions with industry IoT players around market fit. As part of these industry discussions and market research, we identified that LWELs can have a considerable societal impact in low-power place-and-forget applications, particularly given the high growth in IoT devices globally. A pain point identified by IoT players was the security of IoT devices, with more secure IoT protocols requiring more energy. The ability of LWELs to boost indoor PV efficiency, could lead to the next generation of secure IoT devices. We will investigate the integration of LWELs with IoT devices, forming a demonstration kit for industry input, with future research funding. |
| First Year Of Impact | 2023 |
| Sector | Digital/Communication/Information Technologies (including Software),Energy |
| Impact Types | Societal Economic |
| Description | Emergency Grants |
| Amount | £19,716 (GBP) |
| Funding ID | 22.39(m) |
| Organisation | University of Cambridge |
| Department | Isaac Newton Trust |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 03/2023 |
| End | 07/2023 |
| Description | Grant to Support Knowledge Exchange |
| Amount | £500 (GBP) |
| Funding ID | FBYMQ |
| Organisation | The Institute of Materials, Minerals and Mining |
| Sector | Charity/Non Profit |
| Country | United Kingdom |
| Start | 06/2023 |
| End | 07/2023 |
| Description | Impact Acceleration Account - University of Cambridge |
| Amount | £13,260 (GBP) |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 03/2023 |
| End | 05/2023 |
| Description | Researcher Development Grant |
| Amount | £500 (GBP) |
| Funding ID | D23-9980249640 |
| Organisation | Royal Society of Chemistry |
| Sector | Charity/Non Profit |
| Country | United Kingdom |
| Start | 06/2023 |
| End | 07/2023 |
| Description | Royce Facilities Access Scheme |
| Amount | £4,298 (GBP) |
| Funding ID | MAN-YR7-044 |
| Organisation | Henry Royce Institute |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 03/2023 |
| End | 03/2023 |
| Description | Collaboration with McMaster University |
| Organisation | McMaster University |
| Country | Canada |
| Sector | Academic/University |
| PI Contribution | Expertise in the area of Luminescent Solar Concentrators Hosting a 3-month PhD placement from McMaster Providing access to equipment and materials |
| Collaborator Contribution | Training of staff/transfer of knowledge in area of waveguide encoded lattices Hosting of research staff (2 week placement) Provision of samples and access to equipment |
| Impact | Multidisciplinary collaboration between Materials Science (Cambridge) and Chemistry (McMaster) Award of Mitacs Globalink Research Award Abroad (2022) to Kathryn Benincasa for 3 month placement in Cambridge UKRI Impact Acceleration account (Rapid Response) award (2023, £13,260): "Perpetual powering of the Internet-of-Things using ambient light" - This funding was awarded to carry out detailed market research for luminescent waveguide-encoded lattice-enhanced photovoltaics as power sources for Internet of Things devices. Priority patent filing: Luminescent Waveguide Encoded Lattices (LWELs) Inventors: Kathryn Benincasa, Rachel Evans, Takashi Lawson, Kalaichelvi Saravanamuttu, Helen Tunstall Garcia, Provisional US patent application: 63472150. Filed June 9th 2023. |
| Start Year | 2021 |
| Description | Cambridge Science Festival 2022 |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | Video describing research into spectral converters for solar cells and online question and answer (Q&A) session as part of Cambridge Science festival. Around 40 people attended the online Q&A and the video has had >200 views since subsequent posting on the Cambridge Materials YouTube channel (600 subscribers). |
| Year(s) Of Engagement Activity | 2022 |
| URL | https://youtu.be/M8TChcEM8to |
| Description | Contributed poster, International Conference on Hybrid and Organic Photovoltaics (HOPV23) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Postgraduate students |
| Results and Impact | 50 people attended a poster session for the conference, which sparked questions and discussion. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.nanoge.org/proceedings/HOPV23/63e4e0cc77da6e5d6fad10ce |
| Description | Contributed talk, 16th International Conference on Materials Chemistry (MC16) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | 50 people attended a contributed talk at an international conference, which sparked questions and discussion afterwards. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.rsc.org/events/detail/72840/16th-international-conference-on-materials-chemistry-mc16 |
| Description | Impulse Entrepreneurship Programme |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Industry/Business |
| Results and Impact | The impulse programme enables the development of high-potential technology and life sciences innovation into commercial propositions. It is an established, 12-week "action-learning" programme that prioritises and develops high-potential business cases. As part of this programme, I discussed the market fit of LWEL technology with a range of business experts (1-10). |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.maxwell.cam.ac.uk/programmes/impulse |
| Description | Invited Seminar - McMaster University, Canada |
| 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 | ~90 undergraduate, postgraduate, postdoctoral and faculty researchers attended an invited seminar on the topic of spectral conversion materials, which encompassed Luminescence Waveguide Encoded Lattices, which sparked questions and debate and new collaborations. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://brockhouse.mcmaster.ca/events/photon-conversion-materials/ |
| Description | Invited Seminar, University of Dalhousie, Canada |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | ~50 undergraduate, postgraduate, postdoctoral and faculty researchers attended an invited seminar on the topic of spectral conversion materials, which encompassed Luminescence Waveguide Encoded Lattices, which sparked questions and debate and new collaborations. |
| Year(s) Of Engagement Activity | 2023 |
| Description | Invited Talk, MATSUS Fall 2023 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | ~50 postgraduate, postdoctoral and faculty researchers attended an invited talk at the Materials for Sustainable Development Conference (MATSUS23), Torremolinos, Spain (October 2023) in the #ELMOL - The future of molecular electronics symposium, on the topic of spectral conversion materials, which encompassed Luminescent Waveguide Encoded Lattices. This sparked new collaborations. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.nanoge.org/MATSUSFall23/home |
| Description | Invited Talk, MATSUS Spring Meeting 2024 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | ~50 postgraduate, postdoctoral and faculty researchers attended an invited talk at the Materials for Sustainable Development Conference (MATSUS24), Barcelona, Spain (March 2024) in the #ProMatSol - Exploring Material Properties for Advanced Solar Energy Applications symposium, on the topic of spectral conversion materials, which encompassed Luminescent Waveguide Encoded Lattices. This sparked new collaborations and a new grant application is in progress. |
| Year(s) Of Engagement Activity | 2024 |
| URL | https://www.nanoge.org/MATSUS24/symposia?t=65167d0aa6cd1a04310e9df3 |
| Description | Invited talk, Faraday Joint Interest Group Meeting, Sheffield, UK |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Postgraduate students |
| Results and Impact | ~100 postgraduate, postdoctoral and faculty researchers attended an invited talk at the Royal Society of Chemistry Faraday Joint Interest Group meeting (Sheffield, UK) on the topic of spectral conversion materials, which encompassed Luminescent Waveguide Encoded Lattices, which sparked questions and debate and new collaborations. |
| Year(s) Of Engagement Activity | 2023 |
| Description | The Armourers and Brasiers' Cambridge Forum 2022 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Postgraduate students |
| Results and Impact | The Armourers & Brasiers' Cambridge Forum is an annual event, organised by DMSM under the auspices of the Armourers & Brasiers' Livery Company and sponsored by several companies/organizations. The Forum attracts a wide audience, both academic and industrial. |
| Year(s) Of Engagement Activity | 2022 |
| URL | https://www.msm.cam.ac.uk/forum |