Materials

High-efficiency, semi-transparent perovskite/graphene solar cells created at low cost

High-efficiency, semi-transpar...
The semi-transparent, inexpensive solar cells have a claimed conversion efficiency of around 12 percent
The semi-transparent, inexpensive solar cells have a claimed conversion efficiency of around 12 percent
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The semi-transparent, inexpensive solar cells have a claimed conversion efficiency of around 12 percent
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The semi-transparent, inexpensive solar cells have a claimed conversion efficiency of around 12 percent
Transparent or semi-transparent cells provide greater flexibility and visual appeal than opaque silicon solar cells
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Transparent or semi-transparent cells provide greater flexibility and visual appeal than opaque silicon solar cells
Creator of the semi-transparent, efficient, low-cost perovskite solar cells with graphene electrodes, Doctor Yang Feng (left) of Hong Kong Polytechnic University
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Creator of the semi-transparent, efficient, low-cost perovskite solar cells with graphene electrodes, Doctor Yang Feng (left) of Hong Kong Polytechnic University

With the continued rise in the uptake of solar cells, consumers are now looking at less obtrusive ways to incorporate these in buildings and vehicles. Transparent or semi-transparent cells provide greater flexibility and visual appeal than standard, opaque silicon solar cells, however their relatively high-cost and poor efficiencies have meant that their adoption has been slow. To help remedy this, researchers working at the Hong Kong Polytechnic University (PolyU) have created semi-transparent, efficient, low-cost perovskite solar cells with graphene electrodes.

First generation silicon solar cells have been the mainstay of photovoltaic (PV) energy conversion for many years now due to their high stability and efficient energy conversion, but their opacity and expense mean that alternatives are now being actively sought for modern building and vehicle applications. Thin film PVs (second generation solar cells) are lightweight and flexible, but are expensive because they are created from rare materials using complex structures requiring high-temperature production processes.

Now, utilizing such materials as thin-film perovskite, the third generation of solar cell is currently being developed for commercial use in the not-too-distant future with the promise of greater power conversion efficiencies, simpler fabrication processes, and lower cost.

In this vein, the PolyU researchers have developed their own version of the third generation solar cell using semitransparent perovskite with graphene used as the electrodes. Being exceptionally thin but with high conductivity and low cost, graphene makes an ideal choice for semitransparent solar cells as it allows light to be absorbed from both sides. As such, the researchers envisage these devices potentially able to be used in windows, louvers, and building roof surfaces, thereby increasing the available surface area for collecting solar energy.

Transparent or semi-transparent cells provide greater flexibility and visual appeal than opaque silicon solar cells
Transparent or semi-transparent cells provide greater flexibility and visual appeal than opaque silicon solar cells

With a claimed power conversion efficiency of around 12 percent, the PolyU solar cells outperform standard transparent and semi-transparent versions hands-down. The potential to be produced at less than HK $0.50 (US $0.06)/Watt also means a greater than 50 percent saving on thecost of conventional silicon solar cells.

While graphene has been around for more than a decade now and is highly-efficient as a conductor in its own right, the PolyU researchers decided to further enhance the conductivity of graphene to meet their specific requirements. To do this, the graphene was coated with a patina of PEDOT:PSS conductive polymer (poly(3,4-ethylenedioxythiophene)polystyrene sulfonate) – the same ingredient recently used by KAIST scientists in the production of weavable LED fibers – that also acted as an adhesion layer to the perovskite during the process of lamination.

To promote power conversion efficiency, the researchers found that by multilayering graphene through chemical vapor deposition to create transparent electrodes, the sheet resistance of the electrodes was additionally reduced while the exceptional transparency of the electrodes was retained. Finally, the performance of the device was further improved by enhancing the degree of contact between the top graphene electrodes and the hole transport layer on the perovskite film.

According to the researchers, the exceptional flexibility of graphene and the simplified preparation of the cells means that the PolyU device could be eminently suitable formass production via direct printing or using a roll-to-roll process. In this way, semitransparent solar cells may well provide a greater uptake of PV panels across markets not currently serviced by traditional, opaque devices.

The results of this research were published in the journal Advanced Materials.

Source: Hong Kong Polytechnic University

6 comments
Douglas Bennett Rogers
Would the gain be higher with a reflective sheet behind?
Jessie
So by any chance is the US govt going to backwards engineer this so we can produce it as well? Aside from china trying to flood our markets with cheap solar power to wipe out our solar industry so we are reliant on them, china itself sinks billions into its own industry making what wasnt affordable, affordable. As it is, china is responsible for BILLIONS of dollars with or damage to homes thanks to chinese drywall and many other 'gifts' that have killed people or made them vary sick. Including the cadmium toys for kids(worse then lead). I think its safe to say that we should backwards engineer this, have the govt sell it and use all that money to pay back the people that china has screwed that our govt will not protect. Either that or make the process open source so anyone can copy it.
pmshah
@Jessie Why do you blame China for your woes? It was Clinton who granted them most favored nation status in return for their large re-election campaign contribution. It was the US corporates who let down the US manufacturing in favour of lower cost Chinese regardless of quality or toxicity. What I can't figure out is how do legislators at every level, beholden to these corporates, get elected over and over again? The very same legislators, who become lobbyists for their benefactors, upon retirement! So blame yourself. BTW and for all you know NSA may already have all the details.
StWils
Shah is right. While there are many reasons to regard China with great distrust there are also reasons to view China as just another international partner. Part Enemy and Part Friend, or "Frenemy". In sharp contrast the major companies owned by the Less-Than-One-Percenters should ONLY be seen as enemies. It is true that a half dozen or so Chinese drywall makers used coal & mining tailings to make very toxic drywall that was exported freely around the whole of the pacific rim nations without any recourse for compensation. It is also true that the Koch brothers have a monopoly on drywall production in North America that effectively "taxes" all new home construction a minimum of twenty percent for no other reason than that they can. So who is the greater threat? Chinese scientists are contributing to the growth of man's knowledge and should appropriately recognized for this. Good for them and also good for all of the rest of us.
xs400
How about the long term durability of the perovskite/graphene solar cells? This could end up being the 'blade' in the razor if we have to replace them like light-bulbs every so often.
EsspeeEllbee
Douglas Rogers- I was thinking the same thing, sort of. Since these sheets are transparent, why not layer them over one another with thin gaps in between each to allow the photons between them. Perhaps with translucent mirrors layered between each? I don't know, but it's a thought. More power/concentration in the same space as currently available commercial panels...