New method addresses problem with perovskite solar cells

• A new technique to manufacturing perovskite solar cells has actually addressed previous problems as well as yielded devices with high effectiveness and superb stability, scientists at the National Renewable Energy Laboratory (NREL) report in the new issue of the journal Science.

Creating very stable and reliable perovskites based upon a rich mixture of bromine as well as iodine is thought about important for the creation of tandem solar cells. The two elements, nevertheless, have a tendency to separate when revealed to light and warm as well as hence restrict the voltage and stability of a solar cell.

" This new growth method can substantially subdue the phase partition," said Kai Zhu, an elderly scientist at NREL, principal investigator on the job, as well as lead writer of the new paper "Compositional texture engineering for highly stable wide-bandgap perovskite solar cells."

The new approach addressed that problem as well as produced a wide-bandgap solar cell with a performance of above 20% and also 1.33-volt photovoltage as well as little change in the efficiency over 1,100 hours of continuous operation at a heat. With this new strategy, an all-perovskite tandem cell acquired a performance of 27.1% with a high photovoltage of 2.2 volts and also good functional stability.

In the tandem cell, the narrow-bandgap layer is deposited on top of the wide-bandgap layer. The distinction in bandgaps permits more of the solar spectrum to be recorded and converted into electricity.

Perovskite refers to a crystalline structure formed by the deposition of chemicals onto a substratum. A high concentration of bromine causes extra rapid crystallization of the perovskite film as well as commonly leads to defects that lower the performance of a solar cell. Different methods have been tried to minimize those issues, yet the stability of wide-bandgap perovskite solar cells is still taken into consideration inadequate.

The recently established strategy builds on work Zhu and his colleagues released previously this year that turned the typical perovskite cell. Using this inverted architectural structure permitted the researchers to increase both performance as well as stability and to easily integrate tandem solar cells.

The NREL-led group used that same architecture and also relocated further away from the standard method of making a perovskite. The traditional method uses an antisolvent related to the crystalizing chemicals to create an uniform perovskite film. The new method counted on what is referred to as gas quenching, in which a flow of nitrogen was blown onto the chemicals. The result addressed the problem of the bromine and iodine separating, leading to a perovskite film with boosted structural and optoelectronic properties.

The antisolvent strategy allows the crystals to grow rapidly as well as uniformly within the perovskite film, crowding each other as well as causing defects where the grain borders satisfy. The gas-quenching process, when related to high-bromine-content perovskite chemicals, forces the crystals to expand with each other, tightly packed inside out, so they become like a solitary grain and dramatically decreases the variety of defects. The top-down growth method forms a gradient structure, with more bromine near the leading as well as less in the bulk of the cell. The gas-quench method was also statistically more reproducible than the antisolvent approach.

The scientists attained an efficiency that surpassed 20% for the wide-bandgap layer and operational stability with less than 5% degradation over 1,100 hours. Coupled with the bottom cell, the device reached the 27.1% efficiency mark.

The researchers likewise tried argon as well as air as the drying gas with similar results, showing that the gas-quench method is a general way for enhancing the performance of wide-bandgap perovskite solar cells.

The new growth method showed the possibility of high-performance all-perovskite tandem gadgets as well as progressed the advancement of other perovskite-based tandem architectures such as those that incorporate silicon.