Hydrazine-free greener solvent based Se and Se-Te thin film solar absorbers

Selenium (Se), a promising single-element absorber, possesses an optimal bandgap of 1.8 eV and a high absorption coefficient (10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">^5</sup> cm⁻¹), making it a strong candidate for photovoltaic applications. When combined with tellurium (Te), another chalcogen, Se enables tunable bandgaps ranging from 1.0 to 1.8 eV, approaching the ideal range for solar energy conversion. In this work, we present the first successful synthesis of Se and Se-Te precursor solutions using a safer, less toxic solution-processing method. Leveraging these solutions, we have fabricated high-performance Se and Se-Te-based solar cells, incorporating TiO₂ nanoparticles as the heterojunction partner. Notably, this is the first report of Se and Se-Te thin-film solar cells fabricated using a low-toxicity amine-thiol-based solvent, without a hole-transporting layer (HTL) in the device structure. These advancements offer significant potential for safer, more efficient solar technologies.