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Donor-acceptor based bulk-heterojunctions (BHJ) are commonly used as the photoactive layer in organic photodetectors (OPDs) to utilize the energetic offset formed at the donor and acceptor interface for exciton dissociation. However, this strategy often complicates optimization procedures and raises the concerns over device reproducibility and stability. Herein, we demonstrate that solution-processed single-component organic semiconductors can operate as efficient OPDs. We use non-fullerene acceptors (NFAs) as the single-component photoactive layer, where the intermolecular charge transfer excitonic (CTE) states are formed within -9 A cm-2), high responsivity (≥ 0.15 A W-1), high specific detectivity (> 1012 Jones) and fast photo-response time (< 10 μs), comparable to the state-of-the-art BHJ OPDs. We find these excellent single-component NFA OPD performances are strongly correlated with the high quadrupole moments of NFA molecules, which generate the energetic offset required for CTE state separation. Our work opens a new way to realize efficient OPD devices using single-component organic semiconductors via solution processing and provides the important molecular design rules required for single-component photoactive materials.

A bulk-heterojunction (BHJ) structure of organic semiconductor blend is widely used in photon-to-electron converting devices such as organic photodetectors (OPD) and photovoltaics (OPV). However, the impact of the molecular structure on the interfacial electronic states and optoelectronic properties of the constituent organic semiconductors is still unclear, limiting further development of these devices for commercialization. Herein, the critical role of donor molecular structure on OPD performance is identified in highly intermixed BHJ blends containing a small-molecule donor and C60 acceptor. Blending introduces a twisted structure in the donor molecule and a strong coupling between donor and acceptor molecules. This results in ultrafast exciton separation (

Materials in which sub-wavelength physical structures, rather than variations in chemical composition, are used to modify the nature of their interaction with electromagnetic radiation form the promising new class of metamaterials. For molecular materials one has an intriguing alternative, namely structuring the conformation or physical geometry of the molecule. In order for this to be an effective methodology one needs the change in conformation i) to engender a significant change in electromagnetic properties and ii) to be spatially controllable to allow patterning of practical structures. In this paper the potential of such an approach is demonstrated through spatial patterning, via masked solvent vapor exposure, of the β-phase conformation in poly(9,9-dioctylfluorene) (PFO). Significantly the conformation change approach preserves a planar film format and is found not to negatively impact on optical gain properties, both very attractive features for optoelectronic and photonic lightwave circuit applications. As a specific demonstration the ability to spatially control the lasing wavelength for samples in which a β-phase conformation is selectively patterned in a glassy PFO film spin coated atop a one-dimensional distributed-feedback grating etched into a spectrosil substrate is shown.

A numerical model based on Berreman’s 4 × 4 matrix approach was developed and used for computational simulation of a cholesteric liquid crystal (CLC) polarizer. Explicit expressions of the 4 × 4 propagation matrices for several optical films, which constitute a CLC polarizer, were presented. Numerical simulations for optical properties of a CLC layer, a linear polarizer and a CLC polarizer were executed, and the simulated results were found to be in fairly good agreement with measured results.

Excellent quality crystals of CsLiB 6 O 10 (CLBO) up to 60×45×20 mm 3 in size have been grown from supercooled melts at constant temperature. The observed variations in habit for crystals grown from different seed orientations may be explained by assuming that CLBO crystallises in an ideal tetragonal bipyramidal form bounded by 8 {1 0 1} faces. Several linear and non-linear optical parameters were determined including the temperature dispersion of refractive index which is described in detail for the first time. The measured type I phase matched second- and fourth-harmonic generation parameters compare favourably with the values calculated from the refractive index data and those reported by previous authors.

A 1.25-Gb/s bidirectional transceiver is designed and fabricated on a filter-integrated PLC platform for access networks. The fabricated transceiver has optical output of 2.2 dBm at 30 mA and minimum sensitivity of −22.7 dBm at 10−12 at a 1.25-Gb/s NRZ signal and crosstalk penalty of 0.8 dB. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 34–36, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21073

Circuit parameters for an equivalent circuit model of a laser diode were extracted with an impedance analyzer. Impedance matching can be achieved by eliminating inductive components of the leads in the package by using lumped chip capacitors, whereas it shows resonance dip in the low-frequency band. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 347–349, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20300

We demonstrate a compact, low cost and practical fluorescence detection system for lab-on-a-chip applications. The system comprises a commercially available InGaN light emitting diode (501 nm) as light source, an organic or silicon photodiode detector, absorptive dye coated colour filters and linear and reflective polarisers. An injection moulded polystyrene microfluidic chip is used as the platform for fluorescence immunoassays for cardiac markers myoglobin and CK-MB. The optical limit of detection (LOD) is measured using a TransFluoSphere® suspension at 5.6 × 10(4) beads µl(-1) which can be equated to ∼3 nM fluorescein equivalent concentration. The LOD for the human plasma immunoassays is measured as 1.5 ng ml(-1) for both myoglobin and CK-MB.

We demonstrated a low-cost packaging of bidirectional transceiver using filter-integrated PLC platform for subscriber access networks. An adiabatic WDM filter was optimized and designed by BPM simulation. We fabricated a bidirectional transceiver using modified multi-chip bonding scheme for flip-chip bonding of active components and V-shaped groove for optical interconnection. As a result, the optical performance of fabricated transceiver satisfied the criteria required by Ethernet passive optical network.

Estimation of bit error probability for transmission performance of intensity modulated optical code division multiplexing in all optical access networks is investigated with homodyne correlation receiver using dual balanced detector. A complete model is offered including correlation properties for prime codes, equivalent receiver circuit noise, and shot noise as well as multiuser interference. According to this model, the transmission characteristics can also be evaluated depending not only on the number of simultaneous users but also on other system parameters and a method for interpreting the effect of code synchronization state is provided.

We investigated the single step third harmonic generation in CsLiB/sub 6/O/sub 10/ (CLBO) crystals for the first time. Since CLBO crystals, like BBO, possess excellent properties for UV generation, they are good candidates for the single step third harmonic generation. We used a pulsed Nd:YAG laser as a light source, which operates with the pulse width of 9 ns and the repetition rate of 10 Hz. Excellent quality crystals of CLBO have been grown from supercooled melts at constant temperature in the authors' laboratory. The crystal was cut and polished so that the effective /spl chi//sup 3/ may have the maximum value for type I phase-matching configuration.

We describe a simple technique for fabricating non-emissive colour filters based on the sensitisation of a highly porous nanostructured metal-oxide film with a monolayer of dye molecules. Ultrafast electron transfer at the oxide/dye interface induces efficient quenching of photogenerated excitons in the dye, reducing the photoluminescence quantum yield by many orders of magnitude. The resultant filters exhibit much less autofluorescence than conventional colour filters (where the chromophore is dispersed in a glass or polymer host), and are a viable low cost alternative to interference filters for microfluidic devices and other applications requiring non-emissive filtering.