Organic Photovoltaic Solar Cells

- What are Organic Solar Cells?

[BBC]: "Manufacturers have long used silicon to make solar panels because the material was the most efficient at converting sunlight into electricity. But organic photovoltaics, made from carbon and plastic, promise a cheaper way of generating electricity.

The term organic relates to the fact that carbon-based materials are at the heart of these devices, rather than silicon. The square or rectangular solid solar panels that most of us are familiar with, require fixed installation points usually on roofs or in flat fields. Organic photovoltaics (OPV) can be made of compounds that are dissolved in ink so they can be printed on thin rolls of plastic, they can bend or curve around structures or even be incorporated into clothing.

Commercial solar photovoltaics usually covert 15-22% of sunlight, with a world record for a silicon cell of 27.3% reached in summer 2018 in the UK. Organics have long lingered at around half this rate, but this year (2018) has seen some major leaps forward. In April 2018 researchers were able to reach 15% in tests. Now a new study pushes that beyond 17%, and with the up to 25% is possible. This is important because according to estimates, with a 15% efficiency and a 20 year lifetime, organic solar cells could produce electricity at a cost of less than 7 cents per kilowatt-hour. In 2017, the average cost of electricity in the US was 10.5 cents per kilowatt-hour, according to the US Energy Information Administration.

- What are Possible Applications?

Flexible, printed solar cells offer a wide range of possibilities. They can work indoors and they can be made semi-transparent, so they could be incorporated into windows and generate power during daylight. They offer huge potential for buildings as they are lightweight so might be ideal for deploying on the roofs of houses in developing countries where structures might not suit heavy silicon. They could be used on the roofs of cars, and in clothes, even in glasses to charge your phone while you are out and about."

- OPV - A Rapidly Emerging PV Technology

[NREL]: "Our primary work focuses on photovoltaic (PV) cell research. But our advances in understanding and creating new materials and processes are also being applied in such areas as organic light-emitting diodes and thin-film-transistor displays. OPV is a rapidly emerging PV technology with improving cell efficiency (currently ~13.2%), encouraging initial lifetime (>5,000 hours unencapsulated), and potential for roll-to-roll manufacturing processes. The building-integrated PV market may find OPV especially attractive because of the availability of absorbers in several different colors and the ability to make efficient transparent devices."

"OPV's great strength lies in the diversity of organic materials that can be designed and synthesized for the absorber, acceptor, and interfaces. Considering the Department of Energy's SunShot Initiative goals, we need to further improve device efficiency and lifetime. We must understand the fundamentals of device operation, including charge-separation processes, charge-transport mechanisms, device physics, and interfacial effects. This will allow us to design more-efficient, stable device architectures based on materials with improved energy-level alignment, spectral response, and transport properties."

[More to come ...]