Researchers at Helmholtz-Zentrum Berlin (HZB) have found that solar cells made of metal halide perovskites achieve high efficiencies and can be produced from liquid inks with little energy input.

Metal halide perovskites are a particularly inexpensive and promising material class for next-generation solar modules.

Perovskite solar cells can be fabricated using coating processes that use liquid inks made from precursor materials and various solvents.

After the coating, the solvents evaporate, and the perovskites crystallize into a homogeneous layer.

The team has now shown how important the composition of precursor inks is to produce high-quality perovskite thin layers. The solar cells, manufactured with the best inks, were tested outdoors for a year and scaled to mini-module size.

On investigating how the different solvent combinations affect the crystallization of the perovskite films, the best perovskite solar cells achieved a certified performance of 22.3% on a laboratory scale.

The team also produced mini solar modules (12.6 cm 2) that achieved efficiencies of roughly around 17%.

It tested the solar cells optimized in this way for a year outdoors. The efficiency remained almost stable in winter and spring and only dropped in the warmer summer months.

“These tests of larger modules under real conditions give us valuable information on how to improve halide perovskite photovoltaics further,” the researchers affirmed.

The team is currently investigating options for scaling up.

“Perovskite photovoltaics is the best solution-processable PV technology available…but we are only just beginning to understand how the complex interaction of the solvent components affects the quality of the perovskite layers,” the researchers said.

This is because unwanted inhomogeneities, such as rib-like structures, can occur when coating the halide perovskite layers on large areas.

However, the researchers said such effects could be minimized by varying the viscosity of the ink.

Researchers at Swansea University in Wales, United Kingdom recently established a low-cost and scalable carbon ink formulation capable of unlocking the potential for manufacturing perovskite solar cells at scale.

Italy-based renewable energy company Enel Green Power, researchers at the National Solar Energy Institute (INES), and the French Alternative Energies and Atomic Energy Commission (CEA) claimed to have achieved a power conversion efficiency of 26.5% for a 2-terminal tandem perovskite solar cell.