In organic bulk heterojunction solar cells (OSCs) donor-acceptor vertical composition profile is one of the crucial factors that affect power-conversion efficiency (PCE). In this simulation study, five different kinds of donor-acceptor vertical configurations, including sandwich type I and type II, charge transport favorable, charge transport unfavorable, and uniform vertical distribution, have been investigated for both regular and inverted OSC structures. OSCs with uniform and charge transport favorable vertical composition profiles demonstrate the highest efficiencies. High PCE from charge transport favorable configuration can be attributed to low recombination because of facilitated charge transport in active layer and collection at electrodes, while high PCE from uniform structure is due to sufficient interfaces for efficient exciton dissociation. OSCs with sandwich and charge transport unfavorable structures show much lower efficiencies. The physical mechanisms behind simulation results are explained based on energy band diagrams, dark current-voltage characteristics, and comparison of external quantum efficiency. In conclusion, experimental optimization of vertical composition profile should be directed to either uniform or charge transport favorable vertical configurations in order to achieve high-performance OSCs.

N,N′-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN2) is an n-type semiconductor exhibiting high electron mobility and excellent air stability. However, the reported electron mobility based on spin-coated PDIF-CN2 film is much lower than the value of PDIF-CN2 single crystals made from vapor phase deposition, indicating significant room for mobility enhancement. In this study, various insulating polymers, including poly(vinyl alcohol), poly(methyl methacrylate) (PMMA), and poly(alpha-methylstyrene) (PαMS), are pre-coated on silicon substrate aiming to enhance the morphology of the PDIF-CN2 thin film, thereby improving the charge transport and air stability. Atomic force microscopy images reveal that with the pre-deposition of PαMS or PMMA polymers, the morphology of the PDIF-CN2 polycrystalline films is optimized in semiconducting crystal connectivity, domain size, and surface roughness, which leads to significant improvement of organic thin-film transistor (OTFT) performance. Particularly, an electron mobility of up to 0.55 cm2/V s has been achieved from OTFTs based on the PDIF-CN2 film with the pre-deposition of PαMS polymer.

In this study, at first, thin films of poly(3‐hydroxybutyrate‐co−3‐hydroxyvalerate) (PHBV) nanocomposites were prepared by adding 1–3 wt % grafted halloysite nanotubes (G‐HNTs). Jute‐PHBV bio‐nanocomposites were then fabricated using these films and chemically treated jute fibers in a compression mold machine. The effect of treatment and modification on jute fiber and halloysite nanotubes (HNTs), and the change in their morphology was investigated using Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM). Flexural and thermomechanical properties were determined using a three‐point bend test and dynamic mechanical analysis (DMA). The results showed separation of fiber bundles with rough fiber surfaces, and grafting of silane coupling agents on fibers and HNTs after the chemical treatment. As a result, a strong bonding was established between the PHBV, G‐HNTs and jute fibers that lead to significant improvements in flexural and thermomechanical properties of jute‐PHBV bio‐nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43994.

In this work, a nondestructive patterning method for organic semiconductors is demonstrated using nanoimprint lithography (NIL) and polymer sacrificial template. After patterning amorphous fluorinated polymer (Teflon-AF) structures by NIL, poly(3-hexylthiophene) (P3HT) thin film is spin-coated on the Teflon-AF template. The sacrificial template is then removed by a fluorinated solvent, leaving patterned P3HT structures on the substrate. P3HT lines and squares of various sizes (0.35 lm to tens of microns) are obtained by this method. This technique is also extended to fabricate passive-matrix organic light-emitting diode arrays for flat-panel display applications. By avoiding oxygen RIE on organic semiconductor, this patterning technique is nondestructive to organic semiconductors. Moreover, this method is capable of making high-resolution (deep submicron) organic semiconductor patterns to potentially enable nanoscale organic electronic devices with high performance or organic integrated systems with high integration density.

Organic–inorganic hybrid perovskite solar cells (PVSCs) have attracted extensive attention due to high efficiency, easy fabrication, and low-cost solution processes. One of the keys to achieve high-performance cost-effective PVSCs is to attain rapid crystallization with controlled morphology of the perovskite films. Herein, the authors report a technique for the rapid crystallization of perovskite with tunable crystal grain size and morphology via a seeded approach. Specifically, a solution of lead iodide (PbI2) was spin coated on a substrate, and a low-concentration solution of methylammonium iodide (MAI) was dropped onto the PbI2 film to form perovskite seeds prior to introducing high-concentration solution of MAI. The seeded nucleation and growth lead to dense and uniform perovskite thin films with controllable crystal grains. This seeded crystallization technique offers an effective way to boost the low-cost manufacture of efficient and reproducible PVSCs.

Perovskite solar cells (PVSC) have drawn increasing attention due to their high photovoltaic performance and low-cost fabrication with solution processability. A variety of methods have been developed to make uniform and dense perovskite thin films, which play a critical role on device performance. Herein, we demonstrate a polymer additive assisted approach with Polyamidoamine (PAMAM) dendrimers to facilitate the growth of uniform, dense, and ultra-smooth perovskite thin films. Furthermore, a lamp annealing approach has been developed to rapidly anneal perovskite films using an incandescent lamp, resulting in comparable or even better device performance compared to the control hotplate annealing. The facile polymer additive assisted method and the rapid lamp annealing technique offer a clue for the large-scale fabrication of efficient PVSCs.

In this study, the properties of bacterial fermentation based poly(hydroxybutyrate-co-hydroxyvalerate)-PHBV thermoplastic biopolymer was investigated by reinforcing natural halloysite nanotubes (HNTs). At first, HNTs were added to PHBV polymer by melt processing technique. The modified PHBV resin was then used to fabricate films using compression molding process. X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile tests were performed. XRD results showed mixed intercalated and exfoliated behavior of HNTs in PHBV matrix with an increase in interplanar spacing and decrease in peak intensity. DSC analysis showed that the crystallinity of PHBV resin increased with the increase in HNTs concentration. Also, the DSC endotherm curve showed dual melting peaks indicating formation of different crystalline phases. Higher melting and recrystallization temperature was found in nanophased samples in comparison to the pure PHBV counterpart. The thermal stability, activation energy, tensile and viscoelastic properties of nanophased samples were also increased with an optimum at 3 wt. % HNTs loading. Scanning electron micrographs (SEM) revealed river like pattern in neat films indicating a brittle failure in contrast to rougher surfaces observed in nanophased samples.