Black Perovskites Better For Power Conversion

• Perovskite solar cells can help absorb more sunlight if the crystals retain their black state instead of turning into yellow
• To address this, a team of researchers led by Belgium's KU Leuven blinded a thin film of CsPbl3 to a sheet of glass and heated to a temperature of 330°C
• On cooling down to room temperature, the atoms in the crystal were found to stay in the black form

Yellow coloured perovskites are no match for black perovskites in efficiently generating solar power, claim researchers led by Belgium's KU Leuven University. But under room temperature black perovskites eventually turn the crystal into yellow.

To ensure perovskites retain their blackness, an international research team led by Dr Julian Steele of the KU Leuven Centre for Membrane Separations, Adsorbtion, Catalysis and Spectroscopy for Sustainable Solutions (cMAC) blinded a thin layer of caesium lead triiodide (CsPbl3) perovskite solar cells to a sheet of glass by heating the film to a temperature of 330°C. This process causes the perovskites to expand and adhere to the glass. It is then rapidly cooled down to room temperature thereby ensuring atoms in the crystals don't get to move and stay in the black form.

"There are three pillars that determine the quality of solar cells: price, stability, and performance. Perovskites score high on performance and price, but their stability is still a major issue," explained Steele. "Understanding how this mechanism works will help further research to ultimately develop solar panels that use pure perovskite crystals. Since the entry level for processing perovskite-based solar cells is relatively low, they can be very beneficial for people in developing countries operating in a more limited infrastructure."

Partly funded by The Research Foundation-Flanders (FWO), the research work was supplied much of the data by the European Synchrotron Radiation Facility with Ghent University's Centre for Molecular Modeling (CMM) supported with theoretical simulations of the black and yellow phases of the perovskites.

The study was published in Science.