A new method for making metal oxide devices at much lower temperatures uses ultraviolet (UV) irradiation. Yong-Hoon Kim and colleagues used UV light to chemically activate metal particles in a chemical solution; the new metal oxide molecules condensed out of the solution, forming a thin semiconducting film. The process can be performed at room temperature—far lower than the 350° temperatures typical of metal oxide fabrication.

via Using ultraviolet light to fabricate thin flexible electronics | Ars Technica.

The high temperatures are the problem. 350°C is above the melting point of most flexible, transparent substances (e.g. plastics), and real electronic devices need a substrate to give them shape. It doesn’t matter how thin or transparent metal oxide devices are if they must be deposited on thick, opaque, rigid materials.