Perovskites, perovskites, perovskites – one might think the product runs the planet with the number of headlines, but as of yet it still sits outside of the commercial market for solar power. There is, however, some serious advancement. OxfordPV in the UK and the Australians at Greatcell are both moving forward, with research pouring in from many labs globally.
One of the major benefits talked up about perovskites is the attractive price, due to easier production. However it has often been suggested that perovskite products could become more efficient via a property called “carrier multiplication.” Now evidence of that higher theoretical efficiency, per Dr. Chris de Weerd (left) and Dr. Leyre Gomez (right), has been “obtained using three independent experimental approaches, and is conclusive.”
The basic meaning of this research is that the Shockley–Queisser limit of ~33% for a single layer of silicon based solar cells, is now the Gomez-Weerd limit of ~44% for a single layer of perovskite solar cells. From an application standpoint – what this means is that the exact same hardware that was generating 300 or 400 watts is a solar module, using the same module material, same racking, same transportation, mostly same engineering, and same human labor – not the same inverters or balance of system though – can now potentially put out 33% more electricity with similar costs.
De Weerd, who successfully defended her PhD thesis based on this and other research last week, says:
Until now, carrier multiplication had not been reported for perovskites. That we have now found it is of great fundamental impact on this upcoming material. For example, this shows that perovskites can be used to construct very efficient photodetectors, and in the future perhaps solar cells.
The fundamental aspect of “carrier multiplication” is this: generally the excess energy of photons on a solar panel are released via heat because materials only give up a single “valence electron” at a time. However, in material like perovskites – the excess energy can excite an additional valence electron, and this second electron can generate electricity from the same photon. More electricity from the same sunlight.
Of course, we’ve gotten nowhere near silicon-based solar cells efficiency limits of 33% with modern products, and – more importantly – real close to 0% of the world’s current solar power installed is perovskite based. However, the research moves forward.