Photon-Multiplication to boost si photovoltaic power conversion efficiency
Photovoltaics (PVs) cells will play a major role in the worldwide transition to more sustainable sources of energy. There has been a vast scale up in the deployment of PV cells driven by the drastic price reduction of Si photovoltaics (Si-PVs). It is now widely accepted that increases in PV efficiency are key to pushing PV deployment further and continuing to lower costs. However, after decades of research and development Si-PVs are approaching the theoretical limit for power conversion efficiencies (currently 26.7% out of a possible 29.4%) as determined by the Shockley-Queisser limit, due to thermalisation losses. There is currently no commercially deployed technology and can overcome this challenge.
This project will make a proof of concept demonstration of a new technology – a photon multiplication film (PMF), which overcomes these fundamental thermalisation losses by converting high energy photons into double the number of low energy photons using a process called singlet fission. A PMF film could raise the efficiency of the best Si-PVs from 26.7% to 32.5% (a 20% increase in efficiency). This all optical approach has several advantages over other technologies currently being researched such as tandem cells. For instance, since the output of the PMF is photons, they can be directed towards the PV cell without any change in cell design, making it a ‘drop in’ solution, compatible with 95% of current PV manufacturing capacity as well as future designs and hence requiring little or no change to current manufacturing lines and hence very low capital expense. This PoC project will produce a prototype PMF integrated on top of a Si-PV and demonstrate a gain in power conversion efficiency, thus opening up a new technological area, which will help deliver both economic, societal and environmental benefits.