Research Teams Seek Increased Efficiency of Perovskite Solar Cells

Developing efficient perovskite solar material has been a task that has flummoxed research teams around the world. Two teams of researchers have uncovered new developments in the technology, but their findings range from promising to challenging.

First, the good news. Researchers from Stanford and Oxford Universities have created a new solar cell that combines two perovskite solar materials to increase efficiency and lower a building’s carbon footprint.

“When used together with another perovskite semiconductor that specializes in harvesting visible photons, we are able to convert solar energy into electricity with 20% efficiency,” says Tomas Leijtens, co-lead author of the study. “We think we will be able to increase the efficiency to 30%, which would revolutionize the solar industry.”

How It Works

The devices consist of two perovskite solar cells (PSCs) stacked together. Each cell is printed on glass, but the technology could also be applied to plastic.

Previous studies from Stanford and Oxford showed that adding a perovskite layer can improve the energy efficiency of silicon solar cells, which has been an impediment to solar technology. However, a device consisting of two all-perovskite cells would be cheaper and less energy-intensive to build.

On a less optimistic note, researchers of the Energy Materials and Surface Sciences Unit at the Okinawa Institute of Science and Technology Graduate University have been studying the short lifespan of methylammonium lead iodide perovskite (MAPbI₃), a common type of perovskite material.

Dr. Shenghao Wang, first author of the study, suggests that fixing the degradation of MAPbI₃ perovskites might not be possible. After removing factors that have been cited as possible degraders of MAPbI₃ perovskites (moisture, atmospheric oxygen and heat), Wang’s team found that their solar cells continued to degrade anyway.

“We found that these PSCs are self-exposed to iodine vapor at the onset of degradation, which led to accelerated decomposition of the perovskite material into lead iodide,” Wang explains. “Because of the relatively high vapor pressure of iodine, it can quickly permeate the rest of the perovskite material, causing damage of the whole PSC.”

This does not mean perovskite materials won’t work in solar cells. In fact, Professor Yabing Qi, another author of the study, explains that their “experimental results strongly suggest that it is necessary to develop new materials with a reduced concentration of iodine or a reinforced structure that can suppress iodine-induced degradation, in addition to desirable photovoltaic properties.”