Holographic three-dimensional (3D) displays provide realistic images without the need for special eyewear, making them valuable tools for applications that require situational awareness, such as medical, industrial and military imaging. Currently commercially available holographic 3D displays use photopolymers that lack image-updating capability, resulting in restricted use and high cost. Photorefractive polymers are dynamic holographic recording materials that allow updating of images and have a wide range of applications, including optical correlation, imaging through scattering media and optical communication. To be suitable for 3D displays, photorefractive polymers need to have nearly 100% diffraction efficiency, fast writing time, hours of image persistence, rapid erasure, and large area-a combination of properties that has not been shown before. Here, we report an updatable holographic 3D display based on photorefractive polymers with such properties, capable of recording and displaying new images every few minutes. This is the largest photorefractive 3D display to date (4 x 4 inches in size); it can be recorded within a few minutes, viewed for several hours without the need for refreshing, and can be completely erased and updated with new images when desired.

The addition of small amounts of dodecylamine-capped Au nanoparticles into the active layer of organic bulk heterojunction solar cells consisting of poly(3-octylthiophene) (P3OT) and C(60) was recently suggested to have a positive impact on device performance due to improved electron transport. This issue was systematically further investigated in the present work. Different strategies to incorporate colloidally prepared Au nanoparticles with a narrow size distribution into organic solar cells with the more common donor/acceptor system consisting of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C(61)-butyric acid methyl ester (PCBM) were pursued. Au nanoparticles were prepared with either P3HT or dodecylamine as ligands. Additionally, efforts were undertaken to incorporate nearly ligand-free Au nanoparticles into the system. Therefore, a procedure was successfully developed to remove the dodecylamine ligand shell by a postpreparative ligand exchange with pyridine, a much smaller molecule that can later partly be removed from solid films by annealing. However, for all types of nanoparticles studied here, the performance of the P3HT/PCBM solar cells was found to decrease with the Au particles as an additive to the active layer, meaning that adding Au nanoparticles is not a suitable strategy in the case of the P3HT/PCBM system. Possible reasons are discussed on the basis of detailed investigations of the structure, photophysics and charge transport in the system.

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The chemical design of a polymer can be tailored by a random or a block sequence of the comonomers in order to influence the properties of the final material. In this work, two sequences, PCPDTBT and F8BT (F8), were polymerized to form a block or a random copolymer. Differences between the various polymers were examined by exploring the surface topography and charge carrier mobility. A distinct surface texture and a higher charge carrier mobility was found for the block copolymer with respect to the other materials. Solar cells were prepared with polymer:PC 71BM blend active layers and the best performance of up to 2% was found for the block copolymer, which was a direct result of the fill factor. Overall, the sequences of different copolymers for solar cell applications were varied and a positive impact on efficiency was found when the block copolymer structure was utilized

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In this study, the conducting channel in poly(3-hexylthiophene) (P3HT) organic field effect transistors (OFETs) was investigated. The effect of varying the P3HT layer thickness on the OFET parameters was studied. The threshold voltage and the field effect mobility were determined from both the linear and saturation regime of the OFET output characteristics for all film thicknesses and the results are compared and discussed. A gated four probe technique was used to investigate the formation and evolution of the conducting channel by monitoring changes in potential at different points in the channel during measurement. It was found that the device performance of the OFETs was significantly influenced by the thickness of the P3HT layer. Bulk currents were found to dominate device performance for thicker P3HT layers.

In this study, we demonstrate how the intrinsic properties of a polymer can influence the electrical characteristics of organic field-effect transistors (OFETs). OFETs fabricated with three batches of poly[2-methoxy,5-(3 0 ,7 0 -dimethyl-octyloxy)]p-phenylene vinylene (MDMO-PPV) were investigated. The properties of the polymers were initially investigated using Fourier transform infrared spectroscopy (FTIR), impedance spectroscopy (IS), gel permeation chromotography (GPC), and cyclic voltammetry (CV), respectively. The structure and purity of the polymer batches were found to be very comparable, but the molecular weight (M n and M w ) and polydispersity (PDI ¼ M w /M n ), varied between the samples and the HOMO and LUMO levels of the polymers were found to depend on the molecular weight properties. OFETs were then fabricated with the polymers and electrically characterized. It was observed that the channel current and the field-effect mobility increase with increasing polymer molecular weight. The output characteristics of the transistors, on the other hand, were found to depend on the PDI of the polymer. Saturation of the channel current occurs at higher source-drain voltages and short-channel behavior was observed to start at longer channel lengths for polymers with a higher PDI. This behavior is observed to be thickness dependent, and the shortchannel behavior was more pronounced for thicker MDMO-PPV films. These results are explained in terms of influences of chain packing and ordering and high bulk currents on the FET output and transistor parameters.

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