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

Abstract

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.

Photonic post-processing of a multi-material transparent conductive electrode architecture for optoelectronic device integration

“…49 This amorphous precursor is shown to crystallize using 405 or 532 nm laser sources, under environmental conditions. [36][37][38] It is also suitable for photonic postprocessing using a wide-spectrum light source such as a xenon ash lamp. This crystalline TiO 2 layer can be used in the fabrication of optoelectronic devices, whether as the active layer of a photodetector or as an electron transport layer.…”

Synthesis of vacancy-rich titania particles suitable for the additive manufacturing of ceramics

“…To move one step closer towards the laser-assisted additive ceramic manufacturing, we used a standard commercial filament-based 3D printer mounted with a low-power 405 nm laser printhead. This procedure has been detailed by our team in previous reports 94 . Using this laser, we used 140 W mm −2 (for anatase) and 215 W mm -2 (for rutile) to form a complex mosaic pattern combining amorphous, anatase and rutile polymorphs originating from the vacancy-rich amorphous TiO 2 94 .…”

“…This procedure has been detailed by our team in previous reports 94 . Using this laser, we used 140 W mm −2 (for anatase) and 215 W mm -2 (for rutile) to form a complex mosaic pattern combining amorphous, anatase and rutile polymorphs originating from the vacancy-rich amorphous TiO 2 94 . Figure 8 shows it is now possible to spatially organize different crystalline phases with high level of precision within complex architectures and patterns.…”

Deep-learning framework for fully-automated recognition of TiO2 polymorphs based on Raman spectroscopy

“…TiO 2 polymorphs play an essential role in diverse applications ranging from photo-catalysis to energy-harvesting 53 , 54 . Furthermore, researchers have shown that it is possible to have an enhanced room temperature photo conversion by utilising a defect-rich synthesis of TiO 2 55 . Rapid characterization of TiO 2 polymorphs is crucial for several applications such as additive manufacturing 56 .…”