Danish scientists have created solar cells based on selenium using a new laser annealing technique

A team of scientists at the Technical University of Denmark has created a selene-based solar cell by replacing thermal annealing with a new laser annealing strategy.

"In our work, we investigated the potential of this laser annealing strategy specifically for selenium thin film solar cells, and we report a new world record for fill factor, a new world record for ideal factor, and the most advanced of the studies," Rasmus Nielsen, lead author of the study, told the Journal of Photovoltology. "In addition, the laser annealing strategy allows us to control the morphology of the light absorber to an incredible degree."

The proposed laser annealing strategy involves irradiating the selenium absorber through a translucent substrate, which the researchers say results in negligible surface roughness and larger grains. "The crystallization technique is particularly interesting because it enables the selenium absorber to crystallize without heating the substrate," Nielsen also explains.

The team built the battery with a sodium-calcium glass substrate, a tin oxide (FTO) layer, an electron transport layer made of titanium oxide (TiO2), a selenium absorber, a molybdenum oxide (MoOx) layer, and a gold (Au) layer.) Metal contact. TiO2 films are formed by sputtering metal Ti in a reaction atmosphere and at a substrate temperature raised to 400°C. The battery is then annealed for 1 hour at 500°C under a high vacuum.

"The laser annealing of amorphous selenium films is carried out through the substrate," the academics explain. "With this' overlay 'laser annealing strategy, light energy is mainly absorbed near the carrier separation junction,

Rather than an open surface where the selenium can evaporate away again."

Tested under standard lighting conditions, the battery achieved a power conversion efficiency of 5.0% and a record fill factor of 63.7%. The device also achieved a record ideal factor value n = 1.37. The ideal factor indicates how similar the characteristics of a solar cell are to those of an ideal diode.

"Notably, this fill factor value is the highest reported for selenium solar cells, and the fill factor of the laser-annealed sample was repeatably better than that of the hot-annealed control sample regardless of the laser dose range studied." The scientist said. "The increase in the filling factor could be attributed to more optimally aligned grains and flat surface morphology."

The paper "Laser Annealing and Solid Phase epitaxy of Selenium thin Film Solar Cells" published by ACS Publications describes the solar cell.

The same research team introduced a 0.30 cm 2 selenium solar cell in December with an open-circuit voltage of 0.99 V, a world record.

Source: Laser Network