Fabrication and characterization of nanostructured titania films with integrated function from inorganic–organic hybrid materials

Abstract

Nanostructured titania films are of growing interest due to their application in future photovoltaic technologies. Therefore, a lot of effort has been put into the controlled fabrication and tailoring of titania nanostructures. The controlled sol-gel synthesis of titania, in particular in combination with block copolymer templates, is very promising because of its high control on the nanostructure, easy application and cheap processing possibilities. This tutorial review gives a short overview of the structural control of titania films gained by using templated sol-gel chemistry and shows how this approach is extended by the addition of further functionality to the films. Different expansions of the sol-gel templating are possible by the fabrication of gradient samples, by the addition of a homopolymer, by the combination with micro-fluidics and also by the application of novel precursors for low-temperature processing. Moreover, hierarchically structured titania films can be fabricated via the subsequent application of several sol-gel steps or via the inclusion of colloidal templates in a one-step process. Integrated function in the block copolymer used in the sol-gel synthesis allows for the fabrication of an integrated blocking layer or an integrated hole-conductor. Both approaches grant a one-step fabrication of two components of a working solar cell, which make them very promising towards a cheap solar cell production route. Looking to the complete solar cell, the top contact is also of great importance as it influences the function of the whole solar cell. Thus, the mechanisms acting in the top contact formation are also reviewed. For all these aspects, characterization techniques that allow for a structural investigation of nanostructures inside the active layers are important. Therefore, the characterization techniques that are used in real space as well as in reciprocal space are explained shortly as well.

Large-Pore Mesoporous Ho3Fe5O12 Thin Films with a Strong Room-Temperature Perpendicular Magnetic Anisotropy by Sol–Gel Processing

“…As already indicated by AFM and TEM, the degree of pore ordering is not very high and is certainly less pronounced than in other polymer-templated nonsilicate oxides. [31][32][33][34][35][39][40][41][42][43][44] However, considering that the garnet material studied in this work is much more complex than the many binary oxides reported in the literature over the past two decades, the overall structure seems rather well-developed. The GISAXS patterns further indicate significant lattice contraction in the direction perpendicular to the substrate plane as a result of the progressive densification of the inorganic matrix and the associated release of NO x and H 2 O (see TGA-MS data in Figure S3 in the SI) upon heating; the in-plane contraction is negligible.…”

“…28,29 This process goes back to Brinker and coworkers; the basics of EISA have been described in detail in many papers and are not discussed here. [30][31][32][33][34][35] Similar to our recent work on mesostructured Y 3 Fe 5 O 12 films, 36 the synthesis is based on the coassembly of common hydrated nitrate salts with a polymer structure-directing agent (SDA). However, unlike the yttrium compound, the HoIG thin films show no typical signs of superparamagnetism, and further exhibit a large perpendicular magnetic anisotropy.…”

Ordered Mesoporous Thin Film Ferroelectrics of Biaxially Textured Lead Zirconate Titanate (PZT) by Chemical Solution Deposition

“…Both the requirements on polymer structuredirecting agents in general and the fundamental principles of self-assembly and soft-templating have been described in excellent reviews elsewhere and, therefore, are not discussed here. [33][34][35][36][37][38][39][40][41][42] Apart from the synthesis, we show that the KLE-templated PZT thin films exhibit good ferroelectric properties and further have a high degree of biaxial texturing, that is, they possess both in-plane and out-of-plane preferred orientations. Biaxial alignment is common in sol-gel derived (bulk) materials deposited on single crystal substrates, but is unique for polymertemplated ordered mesoporous metal oxide films.…”

Hybrid Photovoltaics – from Fundamentals towards Application

“…In the sacrificial templating strategy frequently used block copolymers were polystyrene-block-polyethyleneoxide (PSb-PEO), [165,166] polyisoprene-block-polyethyleneoxide (PIb-PEO) [167] or pluronics, i.e., block copolymers based on ethylene oxide and propylene oxide (PEG-PPO-PEG). [168,169] Mostly, this approach aimed on fabricating DSSCs.…”

“…[155,156] As a consequence, such block copolymers can be used to create well-defined microstructures and morphologies, either by sacrificial templating or as structure directing agents in a hybrid blend system. [157][158][159][160][161][162][163][164][165] Beyond the novel approaches, which are offered by the use of block copolymers, also the similar strategies as established in the usage of homopolymers can be applied when using block copolymers. Thus, a nanocomposite approach can be done to form the BHJ active layer or a pre-structuring of the inorganic materials followed by a backfilling with the organic one can be selected also when using block copolymers.…”