Scalable Growth of Chalcogenide Thin Films for Flexible Optoelectronic Devices

Abstract

Thin-film photovoltaic technologies offer distinct advantages for enabling lightweight, flexible, and high-specific-power energy systems. Still, their broader deployment, particularly in application-integrated markets, remains constrained by power density, resilience, and manufacturing challenges. This thesis addresses these issues by exploring chalcogenide materials, industrially relevant processes, and robust, light device structures. A design-of-experiment approach is used to optimize a two-step synthesis of Cu(In,Ga)(S,Se)2 absorber layers, revealing strong correlations between process conditions and device performance. Learning from such an approach, high-quality CIGS solar cells are fabricated on ultra-thin glass substrates (<200 μm), demonstrating excellent homogeneity, tuneable bandgaps, and minority carrier lifetimes exceeding 100 ns, coupled with non-toxic, waste-free-processed In2S3 buffer layers to support environmental compatibility. Beyond glass, a detailed review of flexible CIGS architectures on stainless steel is presented, containing a practical guideline by reporting how various research groups mitigate degradation from substrate-induced impurity diffusion. Finally, a scalable selenization technique is introduced for synthesizing phophotovoltaic- grade multilayer WSe2 films, with a lifetime exceeding 100 ns, and made on up to 6-inch wafers in under two hours: An important step toward industrial- scale manufacturing of transition metal dichalcogenide solar cells. These studies offer concrete pathways for advancing thin-film optoelectronics, and especially solar cells, toward scalable, high-performance, and environmentally responsible devices across terrestrial and space-relevant applications.