Solution-Processed Chalcogenide Perovskite Thin Films Utilizing Amine Thiol Chemistry

Growing technological advancements necessitate the development of versatile semiconductor materials capable of addressing diverse challenges. These materials must demonstrate robust stability, natural abundance, environmental friendliness, and tunable properties to cater to diverse applications, such as transistors, photovoltaics, thermoelectrics, LEDs, and more. Additionally, they should enable efficient and high-throughput synthesis. In the domain of photovoltaics, we can recognize two material systems competing to meet these requirements – emerging chalcogenides and lead halide perovskites. Emerging chalcogenides, such as Cu₂ZnSn(S,Se)₄, offer low toxicity and earth-abundant elements but have struggled to achieve high efficiencies. On the other hand, lead halide perovskites are breaking efficiency records but are extremely sensitive to air, and moisture and suffer from toxicity issues.<br/>An emerging class of materials that offers a compelling blend of the exciting properties of chalcogenides and lead halide perovskites are chalcogenide perovskites. Chalcogenide perovskites have shown superior stability and abundance in nature. They exhibit intriguing optoelectronic properties such as a tunable bandgap, high absorption coefficients, defect tolerance, and a high dielectric constant. However, despite their potential, chalcogenide perovskites have been constrained by their basic synthesis procedures, often requiring temperatures as high as 1000°C for extended periods, limiting their practicality.<br/>Solution processing has generally been seen as a low-temperature, ambient-pressure route to synthesize chalcogenide materials with high throughputs. Recent reports by Pradhan et.al provide promising results for solution-processed chalcogenide perovskites. They utilized CS₂ insertion chemistry to enable the synthesis of BaMS₃ materials at moderate temperatures. However, their method produced rough and cracked films with significant residual carbon (DOI: 10.1002/anie.202301049).<br/>This study presents a versatile, moderate-temperature solution-processing synthesis approach for BaZrS₃, a notable chalcogenide perovskite for tandem solar cell applications and for the related BaHfS₃ perovskite, suitable for LED and water-splitting applications. We utilized the well-known alkahest amine-thiol solvent system to blade coat our films. This method produced crack-free films with minimal carbon residue and hence provided a promising step forward for the chalcogenide perovskite research. Subsequently, we conducted comprehensive material, morphological, and optoelectronic characterizations on these films to gain valuable insights that can guide the fabrication of high-performance devices.