• Energy Research

AbstractAdditive manufacturing is becoming increasingly important as a flexible technique for a wide range of products, with applications in the transportation, health, and food sectors. However, to develop additional functionality it is important to simultaneously control structuring across multiple length scales. In 3D printing, this can be achieved by employing inks with intrinsic hierarchical order. Liquid crystalline systems represent such a class of self‐organizing materials; however, to date they are only used to create filaments with nematic alignment along the extrusion direction. In this study, cholesteric hydroxypropyl cellulose (HPC) is combined with in situ photo‐crosslinking to produce filaments with an internal helicoidal nanoarchitecture, enabling the direct ink writing of solid, volumetric objects with structural color. The iridescent color can be tuned across the visible spectrum by exploiting either the lyotropic or thermotropic behavior of HPC during the crosslinking step, allowing objects with different colors to be printed from the same feedstock. Furthermore, by examining the microstructure after extrusion, the role of shear within the nozzle is revealed and a mechanism proposed based on rheological measurements simulating the nozzle extrusion. Finally, by using only a sustainable biopolymer and water, a pathway toward environmentally friendly 3D printing is revealed.

Conjugated polymer (CP)‐di‐ureasil composite materials displaying a tunable emission color from blue to yellow through white have been prepared using a simple sol–gel processing method. The tunability of the emission color arises from a combination of energy transfer between the di‐ureasil and the CP dopant and the excitation wavelength dependence of the di‐ureasil emission. Incorporation of the CP does not adversely affect the bulk or local structure of the di‐ureasil, enabling retention of the structural and mechanical properties of the host. Furthermore, CP‐di‐ureasils display superior thermal and photostability compared to the parent CPs. Thermogravimetric analysis shows that the onset of thermal decomposition can be increased by up to 130 °C for CP‐di‐ureasils, while photostability studies reveal a significant decrease in the extent of photodegradation. Steady‐state photoluminescence spectroscopy and picosecond time‐resolved emission studies indicate that the observed tunable emission arises as a consequence of incomplete energy transfer between the di‐ureasil and the CP dopant, resulting in emission from both species on direct excitation of the di‐ureasil matrix. The facile synthetic approach and tunable emission demonstrate that CP‐di‐ureasils are a highly promising route to white‐light‐emitters that simultaneously improve the stability and reduce the complexity of CP‐based multilayer device architectures.

AbstractPhosphonium‐based polythiophene conjugated polyelectrolytes (CPEs) with three different counterions (dodecylsulfate, octylsulfate and perfluorooctane sulfonate) are synthesized to determine how the nature of the counterion affects the thermal properties, the self‐assembly in thin films and the performance as the cathode interfacial layer in polymer solar cells (PSCs). The counterion has a significant effect on the thermal properties of the CPEs, affecting both their glass transition and crystalline behaviour. Grazing‐incidence wide‐angle X‐ray scattering studies also indicate that changing the nature of the counterion influences the microstructural organization in thin films (face‐on versus edge‐on orientation). The affinity of the CPEs with the underlying photoactive layer in PSCs is highly correlated with the counterion species. Finally, in addition to an increase of the power conversion efficiency of ca 15% when using these CPEs as cathode interfacial layers in PSCs, a higher device stability is noted, compared to a reference device with a calcium interlayer. © 2020 Society of Industrial Chemistry

Single‐junction photovoltaic devices exhibit a bottleneck in their efficiency due to incomplete or inefficient harvesting of photons in the low‐ or high‐energy regions of the solar spectrum. Spectral converters can be used to convert solar photons into energies that are more effectively captured by the photovoltaic device through a photoluminescence process. Here, recent advances in the fields of luminescent solar concentration, luminescent downshifting, and upconversion are discussed. The focus is specifically on the role that materials science has to play in overcoming barriers in the optical performance in all spectral converters and on their successful integration with both established (e.g., c‐Si, GaAs) and emerging (perovskite, organic, dye‐sensitized) cell types. Current challenges and emerging research directions, which need to be addressed for the development of next‐generation luminescent solar devices, are also discussed.

The popularity of polyhedral oligomeric silsesquioxanes (POSS) for use in hybrid organic–inorganic materials and devices has grown in the past two decades due to desirable properties such as good thermal stability and biocompatibility, as well as their potential to be functionalized for a wide range of applications, from polymer composites to optoelectronics. Herein, the role of POSS for photonic applications, including sensing, bioimaging, and optoelectronic devices, is summarized. Functionalized POSS building blocks commonly incorporated with luminescent materials are identified, and areas of potential growth within the field are discussed. The addition of POSS to light‐emitting materials is widely shown to prevent aggregation in organic lumophores and inorganic nanocrystals, leading to reduced photoluminescence quenching. The POSS unit is also capable of acting as a passivating agent for nanocrystals and thin films, improving the emission quantum yields of photoluminescent materials and devices. POSS therefore offers the potential to enhance both the functional and photonic properties of cutting‐edge hybrid technologies.

The ability of different polymer encapsulants to enhance the thermal stability of organolead halide perovskite films has been investigated. Epifluorescence microscopy provides crucial insight into early onset thermal degradation.

A one-pot route to ureasil core–shell nanoparticles that exhibit low polydispersity, high stability and low cytotoxicity is reported.