Laser-Assisted, Large-Area Selective Crystallization and Patterning of Titanium Dioxide Polymorphs

Although ubiquitous in multiple industrial applications, the widespread use of solution-based precursors for crystalline titanium dioxide (TiO2) for optoelectronic device integration remains limited due to its high processing temperature. This limitation generates material compatibility issues and complicates the fabrication steps, especially for low-temperature substrates used in flexible hybrid electronics and low-cost photovoltaics. It is currently possible to crystallize TiO2 at lower processing temperatures, but it requires a carefully controlled atmosphere or metallic doping of the amorphous precursor and can only achieve a low-yield conversion of the precursor. Herein, a qualitative method is presented for the processing of an amorphous photosensitive precursor to achieve high-yield conversion to highly crystalline TiO2 at room temperature and in ambient environment without added dopants using a low-energy laser. Moreover, it demonstrates the ability to controllably convert precursor solutions to anatase or rutile TiO2 only by adjusting the laser power density. A real potential for the additive manufacturing of TiO2 structures for photocatalysis, printable flexible hybrid electronics, and low-cost photovoltaics using low-energy laser processing that is compatible with heat-sensitive materials and flexible substrates is shown.