Physicists at the University of Exeter have discovered a technique which can ‘funnel’ a charge generated in a solar cell towards an area where it can be extracted as electricity. The team from Exeter say that this discovery could lead to the creation of solar cells with more than triple the efficiency of current technologies, predicting conversion efficiencies of more than 60%.
In the paper ‘Strain-engineered inverse charge-funnelling in layered semiconductors’, published in the journal Nature Communications, the researchers describe working with the atomically thin semiconductor hafnium disulphide (HfS2), which is oxidized using a laser technique.
In testing this material, the team observed the charge funneling effect, and note its potential for use in high efficiency solar cell concepts. “Future studies of the effects of bandgap engineering on the carriers recombination lifetimes could elucidate the physical mechanisms behind this improvement and may shed light on the role of hot-carriers in such strained devices for photovoltaic applications,” states the paper. “In particular, charge funnelling could allow carriers excited above the bandgap to be extracted before their excess kinetic energy is lost through cooling, enabling solar cells relying on this phenomena to overcome the Shockley−Queisser limit and bring their efficiency above 60%.”
“The idea is similar to pouring a liquid into a container, as we all know it is much more efficient if we use a funnel,” says lead author Adolfo De Sanctis, explaining the analogy. “However, such charge funnels cannot be realised with conventional semiconductors and only the recent discovery of atomically thin materials has enabled this discovery.”