Stability and Band-Gap Tuning of the Chalcogenide Perovskite BaZrS3 in Raman and Optical Investigations at High Pressures

BaZrS${}_{3}$ belongs to an emerging class of ionic semiconductors that are stable and nontoxic, and offer a direct band gap, strong light absorption, and potential defect tolerance---great for photovoltaic applications. The band gap of the title compound is too high, though, for an optimized single-junction solar cell. High-pressure spectroscopy plus first-principles calculations reveal that this perovskite's structure remains stable when squeezed, while its band gap decreases. These results suggest the use of equivalent $c\phantom{\rule{0}{0ex}}h\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l$ pressure, $e.g.$ by cation alloying with Ti, to tweak the band gap of BaZrS${}_{3}$ for efficient energy harvesting.