IMEC has demonstrated a fully solution-processed organic solar cell, including a spray-coated active layer and a spray-coated metal top contact.
The resulting cell shows power conversion efficiencies above 3%, "a performance comparable to organic solar cells produced by spin coating of the organic layer and vacuum evaporation of the top contact metal", said the Belgian lab. "This is an important step towards producing organic solar cells with cheap and large-area processes."
All other things being equal, spray construction would dramatically cut the cost of making large solar cells on an industrial scale.
The active layer is a spray-deposited mixture of the organic semiconductors P3HT and PCBM, overlaid with ink made from nanometre-scale silver particles, fused by heating.
"The challenges are to add the metal without dissolving the underlying layer, and without damaging it by the temperature needed to sinter the silver nanoparticles," said IMEC.
Spraying the silver caused less damage than other deposition techniques, and the metal particles bonded at 150°C, which is compatible with processing on flexible substrates.
"R&D on organic solar cells has entered the stage where we can consider low-cost high-volume manufacturing, which is essential for the uptake of this technology by the industry," said IMEC organic solar cell team leader Tom Aernouts.
A solution processed organic solar cell, with two electron microscopes revealing different details of the actual structure, including the spray-on silver top contact.