The continued development of solar powered methods of renewable energy remains a vital strategy in the environmentally friendly generation of electricity. One advance making inroads into that market is organic photovoltaic (OPV) technology.
OPV solar cells are cheap and easy to make. They also exhibit good performance, particularly under indoor lighting. These attributes suggest that OPVs not only can handle existing photovoltaic applications and markets but also could enable new ones.
Solar Press, which is investigating flexible plastic OPV modules, says OPV technology is more versatile than most conventional photovoltaics when it is operating under solar light as well as direct and diffused interior lighting. A key design objective for this company is the optimisation of the indoor application of OPV.
Solar Press also believes that OPV’s flexibility, conformability, low weight, and opportunity for custom design make it particularly attractive for integration into sensing devices. The company is considering the development of a power management interface to maximise the extraction and storage of harvested energy to power the sensor and wireless transmitter.
OPV’s uptake has been impressive over the past year. Industry analysts estimate that its market today is €3.5 million, and they expect it to rise to €400 million by the end of this decade
Serious Technical Challenges
All this bodes well for OPV’s future, but the technology needs to clear some serious technical hurdles, particularly low efficiency levels. Also, product lifetime is compromised unless the device is suitably encapsulated, and then it can only survive two to three years.
Development of more effective encapsulation material is needed, but it could raise costs, negating one of OPV’s key advantages. Not surprisingly given its low efficiency and short lifetime, OPV is the subject of many developmental investigations being performed by academic and industrial experts.
A study by ADSD Reports suggests OPV’s low efficiency levels will stay low and the 10% barrier in module performance won’t be broken for another 10 years, despite the many different materials that are either available or can be fabricated to manufacture OPVs.
Currently, OPVs will struggle to outperform more established technologies. But some industry experts believe efficiency levels between 6% and 8% would make OPVs commercially viable, especially since those figures could be achieved while retaining modest manufacturing costs and end prices for the technology.
Yet coupled with the low efficiency is the fact that performance drops drastically after exposure to moisture and oxygen. Fundamentally, the device needs to be completely sealed in solid glass packaging, which could extend OPV life to approximately 10 years. However, the OPV assembly would lose flexibility, which is important for this product.
Consequently, projects are now looking at encapsulation materials that would combine durability and flexibility, particularly plastics or very thin glass substrates that exhibit a limited amount of flexibility. Some of the ideas being looked at are expensive, though, and would erode OPV’s price advantage.
But it’s not all doom and gloom for OPV technology. IDTechEX believes OPVs have made good progress in recent years and are definitely one of the most promising technologies in next-generation photovoltaics. Although OPVs only represent a small part of the entire PV market now, it is gradually growing.
Many technological improvements, such as 10% efficiency achieved from unit cells using new photoactive layer materials, suggest that widespread adoption of the technology could be closer than some industry experts predict.
Mitsubishi would agree. It is pushing its development of OPV technology very hard and says it will have a commercially viable product by 2014. The company has been working with the National Institute of Advanced Industrial Science & Technology and the Tokki Corporation, and it has developed what it claims is the world’s first highly integrated OPV module.
To create the module, laser-scribing technology was used on a glass substrate. Organic semiconductor materials were deposited on the substrate and then divided into several cells with the laser. This technology eliminates the need for deposition mask patterning. Mitsubishi says the new module should improve sunlight conversion efficiency.