Low‐Temperature Liquid Precursors of Crystalline Metal Oxides Assisted by Heterogeneous Photocatalysis

Abstract

The photocatalytically assisted decomposition of liquid precursors of metal oxides incorporating TiO2 particles enables the preparation of functional layers from the ferroelectric Pb(Zr,Ti)O3 and multiferroic BiFeO3 perovskite systems at temperatures not exceeding 350 ºC. This enables direct deposition on flexible plastic, where the multifunctionality provided by these complex‐oxide materials guarantees their potential use in next‐generation flexible electronics.

Photochemical solution processing of films of metastable phases for flexible devices: the β-Bi2O3 polymorph

“…Therefore, the formation of β-Bi 2 O 3 crystals is easy in these films at a low temperature (250 °C) (Figure S3c). The further UV irradiation accelerates crystallization23101245 in a matrix that is dense enough to allow the effective coalescence of the formed crystallites (Table S1). These crystallites will work like seeds for the full crystallization of the tetragonal β-Bi 2 O 3 phase as the irradiation time at 250 °C or the annealing temperature is increased (Figs 1b and S3d), under favorable not-constrained boundary conditions.…”

“…Within the framework of the CSD methodology, sensitive metal coordination complexes have shown a huge potential for the processing of oxide thin films at low temperatures (<400 °C), like several Pb- and Bi-based ferroelectric perovskites1011. These compounds are characterized by reactive metal – to – ligand charge transfer states, where a shift of the electronic distribution can be induced by UV light, resulting in the dissociation of the complex bonds and the formation of the metal – O – metal skeleton of the oxide material236101112. As a result, photochemistry has become a powerful tool for the fabrication of films of crystalline oxides at low temperatures, minimizing the high energy consume of the traditional thermal annealing methods and providing a new pathway to integrate functional oxide layers with flexible polymers212.…”

Low-temperature crystallization of solution-derived metal oxide thin films assisted by chemical processes

“…The strong electronic correlations imposed by the crystal lattice usually rule the behavior of complex transition metal oxides. 7 For example, crystalline oxides with the perovskite structure (ABO 3 , where A and B stand for different metal atoms) show correlations between the electrons of neighboring atoms that lead to ferroelectricity (BaTiO 3 , PbZr 1Àx Ti x O 3 ), multiferroicity (BiFeO 3 , BiMnO 3 ), high-temperature superconductivity (YBa 2 Cu 3 O 7 ), or ferromagnetism (La 1Àx Sr x MnO 3 ). Other oxides show adequate properties in the amorphous state, like post-transition metal oxide semiconductors (Zn-Sn-O, In-Zn-O and In-Ga-Zn-O systems).…”

“…This has pushed the research community to explore alternative fabrication processes with much lower heating demands that can efficiently substitute the traditional thermal annealing of most electronic materials at elevated temperatures. [2][3][4][5] The benefits obtained from decreasing the processing temperature span from minimizing the environmental impact (carbon footprint) to reducing the overall costs of the production line. This is much related to the principles of the so-called ''green chemistry'', where the use of low temperatures and mild conditions is specifically pursued in the synthesis of advanced materials.…”

Bandgap Tunability in Sb‐Alloyed BiVO4 Quaternary Oxides as Visible Light Absorbers for Solar Fuel Applications

“…While the exploration of combinations of these, as well as other materials, is beyond the scope of the present work, because at the present colloidal NCs can be produced with precise tuning in a broad chemical compositional range, this work provides broad access to complex metal oxides with variable composition for a wide range of materials applications . While the central focus of the present work has been on synthesis of semiconductor light absorbers, it is important to note that our synthetic approach has potential to enable materials discovery advances in other research fields, such as batteries and fuel cells, that share many of the same challenges relative to the preparation and tunability of multicomponent metal oxides . Even more broadly, the present work provides further proof that, to confront the material design challenge and to discover new materials with properties suitable to advance specific applications, the interplay between theoretical predictions and experimental work is crucial …”