Researchers improve production of thin, efficient solar cells

Researchers at the Air Force Research Laboratory are nearing thin, wearable electronics and other vital power applications.

Photovoltaics, or solar cells, are a key component in next-generation power applications, but integrating them into Air Force systems has been difficult because the materials used to make the cells are typically thick, opaque, rigid and heavy. Attempts to make thinner, lighter and flexible cells greatly reduced their efficiency, making them impractical for today’s advanced technologies such as flexible electronics and wearable sensors.

According to a story in the Energy Harvesting Journal, to address this issue researchers needed to find an inherently flexible material that could efficiently harvest solar energy. Then they had to find a way to make solar cells thinner, but better able to convert the energy to electricity. Using an inexpensive material called inorganic-organic hybrid perovskite, the team was able to make thin, transparent cells. However, the thinning of this material presented its own challenges.

Located at Wright Patterson Air Force Base near Dayton, Ohio, project scientist Santanu Bag told the journal, “One of the main issues of creating thin layers of perovskite is the formation of surface defects in the form of pinholes. The pinholes generate a high frequency of shunting pathways that prevent the charge from traveling through the absorber layer. This condition results in even greater device inefficiency than is caused by the film thinness itself.”

To solve this problem, the research team exposed the surface of the solar cell to thiourea, an organic compound that acts as a “molecular glue” and introduces favorable interactions on the surface of the light-absorbing layer of the cell. The result is a continuous pinhole-free thin perovskite film that is much more efficient at creating electric power.

According to Bag, these materials are useful not only as solar absorbers in photovoltaic devices, but as semiconductors, a class of materials used in modern computing and lighting devices. Potential applications include photodetectors, field-effect transistors and light-emitting diodes. Bag said new sensor and wearable electronic technologies and applications could also emerge as a result of this innovation.