Researchers have identified a technique for developing perovskite solar cells that significantly increases the area of the cell while maintaining high conversion efficiency, which has been difficult to date. Perovskite solar cells (PSCs) are appealing because they have very high solar-to-electric power conversion efficiency (PCE), and are cheap to manufacture. However, a major drawback of PSCs is their lack of scalability; they currently only reach a maximum area of about 0.1 cm2 while maintaining an attractive PCE of roughly 20%. Here, Xiong Li and colleagues were able to create PSCs with an aperture area of 1 cm2 and an average efficiency of 19.6%. They achieved this by eliminating the blotchy impurities that occur during conventional manufacturing techniques. During the standard manufacturing process, the perovskite solid is precipitated from its reaction mixture by dripping an "anti-solvent" into the center of the perovskite film while it is spun, but this procedure creates a gradient in crystallite sizes and numerous grain boundaries. The researchers correct this flaw by using a vacuum technique, called vacuum-flash solution processing (VASP), that enables well-controlled removal of the solvent to induce precipitation. VASP, in combination with a rapid heat annealing treatment, boosts the quality of the perovskite intermediates and slows down crystal growth, resulting in highly oriented, crystalline perovskite films, the authors show. This development is an incremental, but significant step towards larger PSCs with high efficiencies.
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