Organically modified silica (ORMOSIL)-coated dye-sensitized solar cells (DSSCs) with improved energy conversion efficiency are demonstrated. ORMOSIL-coated DSSC surfaces exhibit omnidirectional low reflectivity over a broad range of wavelengths (400–800 nm). The short-circuit current density (JSC) is enhanced up to 23% at normal incidence (θ=0 deg) as a result of ORMOSIL coating. In addition, JSC enhancement is even higher at larger angles of incidence; 84% enhancement was observed at θ=30 deg. Moreover, ORMOSIL coating is superhydrophobic with a contact angle of 155 deg.
We present the design, fabrication, characterization of spatially variable infrared filter and a demonstration
of the filter as a simple infrared spectrometer. A varying photonic band gap filter which consists of thermally
evaporated, high refractive index contrast amorphous chalcogenide glass multilayers, makes the structure suitable
to be used as spectrometer. Due to graded thickness structure, the filter exhibits a position dependent stop band
and a cavity mode ranging from 2 to 8 μm wavelengths. It is demonstrated that the filter can be used to detect
absorption peaks of common gases in the cavity mode range of the filter.
Photonic crystals are three dimensional periodic structures having the property of reflecting the electromagnetic (EM) waves in all dimensions, for a certain range of frequencies. Defects or cavities around the same geometry can also be built by means of adding or removing material. The electrical fields in such cavities are usually enhanced, and by placing active devices in such cavities, one can make the device benefit from the wavelength selectivity and the large enhancement of the resonant EM field within the cavity. By using coupled periodic defects, we have experimentally observed a new type of waveguiding in a photonic crystal. A complete transmission was achieved throughout the entire waveguiding band. The transmission, phase, and delay time characteristics of the various coupled-cavity structures were measured and calculated. We observed the eigenmode splitting, waveguiding through the coupled cavities, splitting and switching of electromagnetic waves in waveguide ports, and Mach-Zender interferometer effect in such structures. The corresponding field patterns and the transmission spectra were obtained from the finite-difference-time-domain (FDTD) simulations. We developed a theory based on the classical wave analog of the tight-binding (TB) approximation in solid state physics. Experimental results are in good agreement with the FDTD simulations and predictions of the TB approximation.
We investigate the localized coupled-cavity modes in two- dimensional dielectric photonic crystals. The transmission, phase, and delay time characteristics of the various coupled-cavity structures are measured and calculated. We observed waveguiding through the coupled cavities, splitting of electromagnetic waves in waveguide ports, and switching effect in such structures. The corresponding field patterns and the transmission spectra are obtained from the finite- difference-time-domain (FDTD) simulations. We also develop a theory based on the classical wave analog of the tight- binding (TB) approximation in solid state physics. Experimental results are in good agreement with the FDTD simulations and predictions of the TB approximation.
Conference Committee Involvement (1)
Nanostructure Integration Techniques for Manufacturable Devices, Circuits, and Systems: Interfaces, Interconnects, and Nanosystems