Nanoposts of 10-40 nm top diameter on an InGaN/GaN quantum well structure were fabricated using electron-beam lithography and inductively coupled plasma reactive ion etching. Significant blue shifts up to 130 meV in the photoluminescence (PL) spectrum were observed. The blue-shift range increases with decreasing post diameter. For nanoposts with significant strain relaxation, the PL spectral peak position becomes less sensitive to carrier screening. On the basis of the temperature-dependent PL and time-resolved PL measurements and a numerical calculation of the effect of quantum confinement, we conclude that the optical behaviours of the nanoposts are mainly controlled by the combined effect of 3D quantum confinement and strain relaxation.

D–A conjugated molecules are complicated in both their molecular and their packing structures. In this perspective, we summarize more than 40 crystal lattices of conjugated oligomers to identify the morphological influence of each building block on the D–A molecules. These lattice structures reveal not only the packing preferences of the conjugated oligomers but also the conformational disorder in the lattices. The presence of this disorder in slowly grown crystals implies that attaining total long-range conformational order is challenging for D–A oligomers, which are structurally complicated and readily distorted and which have building blocks of incommensurate packing dimensions. In optoelectronic applications, a decreased duration of processing can prevent ordering and trap the thin films of D–A oligomers from becoming crystalline phases. Although D–A oligomers conform to packing principles in the formation of a single crystal, their phase behaviors in the formation of active thin films are much more difficult to comprehend. Continuous advances in methods of characterization are still strongly required for the steps of attaining a true structure–property relation of D–A oligomers in active films for optoelectronic applications.

A practical approach to fabricate textured GaNbased light-emitting diodes (LEDs) by nanosphere lithography is presented. By spin coating a monolayer of SiO 2 nanoparticles as the mask, textured LEDs can be fabricated. Both textured p-GaN and textured indium tin oxide LEDs show significant improvement over conventional LEDs without damaging the electrical characteristics. The results show that the method is promising for manufacturing low-cost high-efficient GaN-based LEDs.

An A−D−A oligomer, DTS(F 2 BT) 2 , was synthesized; its structural evolution was studied with DSC, POM, 2D-WAXD, and in-situ GI-XRD. The structural evolution of DTS(F 2 BT) 2 is stepwise and kinetically slow. Both rapid drying and the presence of PC 71 BM trapped DTS(F 2 BT) 2 in a less ordered nematic (N) phase. PDMS-assisted crystallization enabled a pristine DTS(F 2 BT) 2 thin film to attain a more ordered equilibrium phase, and enhanced the OFET mobility of DTS(F 2 BT) 2 . In OPV devices, DIO additive drove the DTS(F 2 BT) 2 domains in the DTS(F 2 BT) 2 :PC 71 BM blended film from the N phase toward the equilibrium phase, and resulted in enhanced OPV performances. These results reveal the slow ordering process of the A−D−A oligomer, and the importance of monitoring the degree of structural evolution of the active thin films in organic optoelectronics.

Structural analysis of PTh4FBT suggested that the highly crystalline nature of PTh4FBT is related to its zero c-shift co-facial packing.