Carbon electrode for roll-to-roll perovskite solar cell manufacturing
Swansea University has developed a carbon ink for low cost roll-to-roll (R2R) production of perovskite solar cells.
Using slot die coating in a roll-to-roll (R2R) process, researchers from the Innovation and Knowledge Centre at Swansea University (SPECIFIC) have established a way to create fully printable perovskite cells. Roll-to-roll production for lightweight, low cost uncoated perovskite cells is a key area of research at the centre.
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The team searched for an alternative to the gold electrode that is typically applied using an expensive and slow evaporation process after the device has been printed.
“The key was identifying the right solvent mix, one which dries as a film without dissolving the underlying layer,” said Dr David Beynon, Senior Research Officer at SPECIFIC. “X-ray diffraction analysis showed carbon electrode ink is capable of this when formulated with an orthogonal solvent system. This layer can be applied continuously and compatibly with the underlying layers at a low temperature and high speed.”
The group says the carbon electrode detailed in Advanced Materials opens up full roll to roll production for the first time. This provides a similar photovoltaic performance to the conventional evaporated gold electrodes as part of a small-scale device on a rigid glass substrate with power conversion efficiencies (PCE) of 13-14%. It also outperforms gold at higher temperatures and has better long-term stability.
The cell is built from an unencapsulated low-temperature n–i–p device architecture in which the typical hole transport layer (HTL) is replaced with a lower cost and humidity/thermally stable PEDOT layer coated directly onto the perovskite. A carbon ink was developed that is fully compatible with the underlying layers of the device structure and rheologically compatible with R2R slot-die coating and compares well to previous reports of R2R-coated devices with evaporated metal contacts.
A fully R2R coated device, which was printed onto a 20-metre-long flexible substrate, produced a stabilised power conversion efficiency of 10.8%.
“The most important part of this project was coating the carbon entirely, R2R, a new process of working with perovskite photovoltaics, which helps to scale up easier,” said Dr Ershad Parvazian, Postdoctoral Researcher at SPECIFIC. “For a few years now, the efficiency of these devices has been increasing, with the expectation that they could be fully printed. This work has proved that.”
The process has been designed and made, assessed and analysed over the last four years, in detail, adapted and improved, opening up the possibility of printing and installing millions of meters of solar cells.
“We need to start making something that really looks like a solar panel. We can then install them on buildings and understand how close we are to delivering on the promise of UK based manufacturing of green renewables,” said Watson.
Other roll to roll electronics articles
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- Patent filing marks start of roll to roll flexible solid state battery
- Roll-to-roll printing for flexible silicon electronics
- Roll-to-roll process supports over-molded LEDs on flexible foil
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