Singlet Fission Photon Multipliers - Adding Efficiency to Silicon Solar Cells

Lead Research Organisation: University of Cambridge
Department Name: Physics


Solar energy can make a major contribution to global energy supply, but for this renewable energy source to make a major impact it will need to compete on cost with conventional sources of energy. Silicon solar cells are the incumbent photovoltaic technology, and have benefited from huge reductions in manufacturing costs over the last 5-8 years. Now that the module cost is no longer the largest component of the installed system cost, further reductions in the cost per installed Watt require increases in the cell efficiency. However, single-junction cells such as silicon are fundamentally limited by the fact that the energy of the solar spectrum in excess of the semiconductor bandgap energy is lost as heat.

We aim to develop a simple active film that can be applied to the front surface of a silicon (or any other) solar cell that will increase the cell efficiency by up to 4% (e.g. from 20% to 24%). We will do this by capturing the high-energy photons from the solar spectrum and converting them to two lower-energy photons that can be absorbed in the solar cell without energy losses to heat. This will be achieved using the process of singlet exciton fission which occurs in certain organic materials, converting the spin-0 singlet state produced by photon absorption into two spin-1 triplet states. We have very recently demonstrated that it is possible to transfer these non-emissive triplet states onto inorganic semiconductor nanoparticles, which can then efficiently emit photons that could be absorbed by an underlying solar cell.

In this project, we will optimise, engineer and demonstrate photon multiplier films based on the approach described above, providing a low-cost efficiency enhancement for silicon solar cells that can be implemented without re-engineering of the electrical structure of the cell.

Planned Impact

If this proposal achieves its ambitious targets then on a 5-10 year timescale we will see a fission photon multiplier film on every solar cell in the world. The value of a 10% relative increase in efficiency would amount to $10bn for a projected $100bn annual PV market.

Improving the cost-effectiveness of photovoltaic systems will accelerate their deployment, thus bringing global environmental benefits through carbon emissions reduction. At the top of the chain of commercial beneficiaries will be the global photovoltaics industry which will benefit through enhanced sales of high-performance systems. The commerical opportunity within the UK is to capture the added value arising from the fission converter by selling films, materials and/or formulations, or by licensing device structure, materials and process IP into the global PV industry. Further down the supply chain we identify opportunities for materials suppliers, both in the organic and inorganic nanoparticle spheres. We emphasise that we are offering an "add-on" product that will not require redesign of the underlying cell technology or manufacturing process, and that this provides a much more straightforward pathway to impact than for new cell technologies.


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Description We have discovered that it is possible to harness triplet excitons generated by the process of singlet fission by attaching fission molecules as ligands on emissive PbS nanoparticles.
Exploitation Route In the development of photon multiplier films to enhance the efficiency of silicon solar cells.
Sectors Energy

Description The findings have been the subject of a number of successful Innovate UK applications in collaboration with Eight19 Ltd to scale up the technology.
First Year Of Impact 2015
Sector Electronics,Energy
Impact Types Economic

Description Energy Catalyst Round 4
Amount £232,297 (GBP)
Funding ID 132952 
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 11/2017 
End 10/2018
Description Materials & Manufacturing Round 2
Amount £601,670 (GBP)
Funding ID 103757 
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 10/2017 
End 09/2019
Title Research data supporting "Contrasting effects of energy transfer in determining efficiency improvements in ternary polymer solar cells". 
Description GIWAXS data of polymer and polymer:fullerene blend thin films. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Title Research data supporting "Engineering Molecular Ligand Shells on Quantum Dots for Quantitative Harvesting of Triplet Excitons Generated by Singlet Fission" 
Description This dataset consists of graphical and tabular data in an Origin file format. The file includes UV-Vis absorption, PLQE, kinetic modelling, transient PL and absorption, steady-state PL and excitation spectra and magnetic field dependent PL measurement data and analysis. Further information about the data collection methods and analysis is available via the journal JACS, at 10.1021/jacs.9b06584. The Origin file "Analysis.opju" contains the data for all plots presented in the paper and SI titled "Engineering Molecular Ligand Shells on Quantum Dots for Quantitative Harvesting of Triplet Excitons Generated by Singlet Fission", along with additional data surrounding the analysis of the presented data. The file is separated into folders sorted by experiment. Figures used in the paper are prefixed with either "Main Fig" or "SI" followed by a brief description of the figure. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Title Research data supporting "Silicon phthalocyanines as dopant red emitters for efficient solution processed OLEDs". 
Description Underlying UV-Vis, PL, EL and OLED current-voltage-luminance data for the samples discussed in the main article. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Description Industrial engagment 
Organisation Eight19
Country United Kingdom 
Sector Private 
PI Contribution Provided materials know-how arising from research programme into industrial partnership for scale-up and development.
Collaborator Contribution Provided scale-up and development pathway.
Impact Innovate UK applications and engagement with cell manufacturers
Start Year 2016
Description There is provided a ternary photon multiplier film. The photon multiplier film comprises an organic semiconductor material capable of multiple exciton generation and a luminescent material in a host material, wherein the bandgap of the luminescent material is selected such that the triplet excitons formed as a result from the multiple exciton generation in the organic semiconductor can be energy transferred into the luminescent material. 
IP Reference WO2018189527 
Protection Patent application published
Year Protection Granted 2018
Licensed Yes
Impact Further development of photon multiplier technology