In an SST-exclusive series of blogs, imec reports from its International Technology Forum this week in Brussels. Tom Aernouts, R&D team leader of organic photovoltaics at imec, reviewed important technical challenges in realizing the promise of low-cost and flexible organic PV.
by Els Parton, science editor, imec
May 27, 2011 — Organic PV is an emerging field, as illustrated by the many startups popping up in the field: SolarPress, Eight19, Heliatek, etc. Many of these new start-ups are backed by large companies or investment funds, showing the huge belief in the potential of organic PV. But what is so interesting about a PV technology that targets only 10% efficiency?
Tom Aernouts, R&D team leader organic photovoltaics at imec, showed a benchmarking graph of all different PV technologies in development today. “Even with substantial performance improvements, OPV remains at the lower end of PV technologies,” he noted. Nevertheless, “it’s an extremely interesting technology because of its low cost (potential to go below 0.5 €/Wp), its low weight (< 0.5kg/m2), and mechanical flexibility and transparency.”
All these features are a dream for creative designers and companies, and will open up a whole new application field for PV. Today this creativity is still limited to products such as OPV-integrated bags, chargers, or bus stops with curling roofs. But when the technology gets more mature, its huge potential will unleash, he suggested — for example with applications in building-integrated PV (PV in curtains, windows, walls etc.) Before such things can happen, though, industrial acceptance has to broaden extensively. “Before OPV can really take off, it needs the involvement of more players in the value chain, such as equipment suppliers, device manufacturers and integrators,” Aernouts said. And gathering all these parties is an important goal also within imec’s research program on organic PV.
Of course, there is also a lot to be done on the technology side before OPV will reach full commercialization. Aernouts explained that the evolution toward higher conversion efficiencies is on schedule, partly thanks to the work of the numerous startup companies. But there still remain some important challenges in increasing lifetime and a clear demonstration of the low-cost potential. “The lifetime of OPV cells is influenced by many factors: there is extrinsic degradation due to e.g. intrusion of oxygen and humidity, and there is intrinsic degradation due to e.g. photo-degradation, morphology reorganization and interdiffusion,” he explained. “It’s key to gain insight into these degradation mechanisms so we can tackle them.”
The low-cost potential is an important asset of OPV, yet there are only preliminary studies available on cost profiles mainly on lab or pre-pilot fabrication processes. “What we learn from these studies is that the material cost dominates strongly over the processing cost,” Aernouts said. “For example, the transparent (indium tin oxide) electrodes are very costly. Therefore, our research group is looking for cost-effective alternatives based on conductive polymers (e.g. PEDOT) and thin metal layers.”