Researchers develop materials that can revolutionize the use of light for solar energy

Researchers at Columbia University have developed a way to leverage singlet fission to increase the efficiency of solar cells, providing a tool to advance the development of next-generation devices.

In a study published this month in Nature Chemistry, the team details the design of organic molecules capable of generating two excitons per photon of light, a process called singlet fission. Excitons are produced quickly and can live much longer than those generated by their inorganic equivalents, which results in an amplification of the electricity generated by photon absorbed by a solar cell.

"We have come up with a new design rule for simple fission materials," said Luis Campos, an associate professor of chemistry and one of the three principal investigators of the study. "This has led us to develop the most effective and technologically useful intramolecular singlet fission materials to date, and these improvements will open the door to more efficient solar cells."

All modern solar panels operate in the same process: a photon of light generates an exciton, explained Campos. The exciton can then be converted into electric current. However, some molecules that can be implemented in solar cells can generate two excitons from a single photon, a process called singlet fission. These solar cells are the basis for next-generation devices, which are still in their infancy. One of the biggest challenges of working with such molecules, however, is that the two excitons "live" for very short periods (dozens of nanoseconds), making it difficult to harvest them in the form of electricity.

In this study, funded in part by the Office of Naval Research, Campos and his colleagues designed organic molecules that can quickly generate two excitons that live much longer than advanced systems. This is a progress that can not only be used in the generation of new generation solar energy, but also in photocatalytic processes in chemistry, sensors and imaging, explained Campos, these excitons can be used to initiate chemical reactions, which can then be used industry to make drugs, plastics and many other types of consumer chemicals.

"Our group and others have demonstrated the intramolecular fission of singlets, but the resulting excitons were generated very slowly or would not last very long," Campos said. "This work is the first to show that singlet fission can quickly generate two excitons that can live for a very long time.This opens the door to a fundamental study of the behavior of these excitons when they rely on individual molecules, as well as to be effectively put to work in devices that benefit from amplified signals. "

The team's design strategy should also prove useful in separate scientific study areas and present many other unimaginable applications, he added.