Researchers claimed to have developed improved thin perovskite films with reduced defects and better stability under higher temperatures by introducing dimethylammonium chloride as a new crystallization agent after substituting the largely used solvent dimethyl-sulfoxide.

The research was jointly conducted by Oxford University, Monash University, and Australian Centre for Advanced Photovoltaics (ACAP).

During testing, the researchers discovered that the device with dimethylammonium chloride as the solvent operated above the T80 threshold for more than 1,600 hours under the direct sun at 65 degrees Celsius.

The initial time taken by a solar cell to reduce to 80% of its initial efficiency, which is a common benchmark in research, is termed T80.

However, the conventional device that used dimethyl-sulfoxide as a solvent stopped functioning when exposed to high temperatures.

The teams from Oxford and Monash universities observed that devices fabricated with the new solvent attained 70% of their original efficiency under accelerated aging conditions.

The new perovskite solar cells age by a factor of 1.7 for every 10 degrees Celsius increase in temperature, while the same increases two-fold in commercial silicon devices.

Materials scientists worldwide are conducting studies to achieve constant stability in perovskite solar cells to enable mass production and commercialization.

The latest work published in the journal Nature Materials evaluates the perovskite crystallization method, which directly impacts the device’s stability.

The experiment

Conventionally, solvents like dimethyl-formamide or dimethyl-sulfoxide are used in the crystallization process of perovskites.

Using these two solvents often leads to degraded crystal quality and poor microstructure of the polycrystalline perovskite films when exposed to direct sunlight.

In the current experiment, researchers pursued a high-temperature dimethyl-sulfoxide-free processing technique wherein dimethylammonium chloride was used as an additive to control the perovskite intermediate precursor phases.

The scientists subjected large groups of 138 sample devices to aggressive aging and testing under direct sunlight and at high temperatures in the laboratory.

After the team controlled the crystallization process of perovskite solar cells using dimethylammonium chloride, it introduced and tuned the grain size, texturing orientation, and crystallinity of a system with formamidinium-cesium.

Last month, a team of researchers from Northwestern University, the University of Toronto, and the University of Toledo claimed to have developed an all-perovskite tandem solar cell that achieved a power conversion efficiency of 27.4%, which is more than the efficiency of 25.5% achieved by scientists at the U.S. National Renewable Energy Laboratory in June.