On the Potential of Optical Nanoantennas for Visibly Transparent Solar Cells

This study aims to determine the maximum possible energy conversion efficiency of visibly transparent solar cells using the detailed balance limit (also known as the Shockley–Queisser limit) and compare it to the efficiency of traditional single-junction solar cells. To achieve this, a new optical nanoantenna has been designed to absorb incoming light selectively, enhancing the average visible transmission while maintaining high absorption in the infrared and UV regions. The color appearance of the antennas has also been evaluated through colorimetrical characterization. Our findings indicate that it is possible to achieve high average visible transparency and energy conversion efficiency of over 80 and 18%, respectively, by carefully selecting semiconductor materials. Such solar cells are versatile enough to be integrated seamlessly into smart windows, agrivoltaic concepts in open and protected cultivation, mobile devices, and appliances without compromising their appearance or functionality. The dimensions and optics of the proposed antennas and visibly transparent solar cells have been thoroughly discussed

Simplified electrical modeling for dye sensitized solar cells: Influences of the blocking layer and chenodeoxycholic acid additive

Dye sensitized solar cells (DSSCs) have been in the research limelight for some years and plenty of research were devoted to the investigation of material properties for device enhancement. The electrical modeling facilitates the simulation of the device characteristics of the DSSCs. In order to develop highly efficient DSSCs, it is crucial to elucidate the electric mechanism within the cell through the electrical modeling. In this work, we propose a simplified explicit method to estimate the four parameters (photo-generated current (Iph), saturation current (Is), ideality factor (n) and series resistance (Rs)) used in the equivalent circuit by using the single diode model. By using the proposed explicit method, two series of simulated I-V curves (blocking layer and chenodeoxycholic acid additive) were generated from LTspice software by using the experiment data of current–voltage (I-V) measurements reported in our previous research. The simulated I-V curves derived from the software show good fitting to the corresponding experimental I-V curves, which demonstrate that the simplified explicit method reported here can be used to serve as an effective approach to evaluate the electrical properties of the DSSCs

Tunable Multispectral Color Sensor with Plasmonic Reflector

Vertically integrated color sensors with plasmonic reflectors are realized. The complete color information is detected at each color pixel of the sensor array without using optical filters. The spectral responsivity of the sensor is tuned by the applied electric bias and the design of the plasmonic reflector. By introducing an interlayer between the lossy metal back reflector and the sensor, the reflectivity can be modified over a wide spectral range. The detection principle is demonstrated for a silicon thin film detector prepared on a textured silver back reflector. The sensor can be used for RGB color detection replacing conventional color sensors with optical filters. Combining detectors with different spectral reflectivity of the back reflector allows for the realization of multispectral color sensors covering the visible and the near-infrared spectral range

High-mobility microcrystalline silicon thin-film transistors prepared near the transition to amorphous growth

Chan K-Y, Knipp D, Gordijn A, Stiebig H. High-mobility microcrystalline silicon thin-film transistors prepared near the transition to amorphous growth. J. Appl. Phys. 2008;104(5):054506.Thin-film transistors (TFTs) are core elements of novel display media on rigid or flexible substrates, radio-frequency identification tags on plastic foils, and other large area electronic applications. Microcrystalline silicon TFTs prepared at temperatures compatible with flexible substrates (150-200 degrees C) have gained much attention as potential elements for such applications due to their high charge carrier mobilities. Understanding the relationship between the structural properties and the charge transport is essential in realizing TFTs with high charge carrier mobility at low temperatures. In this study, top-gate staggered microcrystalline silicon TFTs were realized by plasma-enhanced chemical vapor deposition at maximum temperature of 180 degrees C. We investigated the correlation between the structural properties of the microcrystalline silicon channel material and the performance of the microcrystalline silicon TFTs. Transistors with the highest charge carrier mobility, exceeding 50 cm(2) /V s, were realized near the transition to amorphous growth. The results reveal that electronic defects at the grain boundaries of the silicon crystallites are passivated by the amorphous phase near the transition to amorphous growth. The crystalline volume fraction of the channel material will be correlated with the transistor parameters such as charge carrier mobility, threshold voltage, and subthreshold slope. (C) 2008 American Institute of Physics

Effect of film thickness on electrochromic performance of sol-gel deposited tungsten oxide (WO3)

In recent year, considerable interest has been addressed towards the high energy usage in buildings for indoor comfort due to the less energy efficient windows. Electrochromic (EC) smart window is a new technology that is capable of changing from transparent to opaque and has the potential in energy saving applications. Tungsten oxide (WO3) is a transition metal oxide with a wide range of applications which include electrochromic (EC) smart windows, displays and rear-view mirrors. In EC smart windows, WO3 is the key element where it is responsible for the colouring and bleaching of the device. Therefore the properties of WO3 will affect the EC performance. In this work, WO3 films were deposited on tin doped indium oxide (ITO) coated glasses via the sol-gel spin-coating technique. The WO3 film thicknesses were varied by means of number of deposited layers. The film thickness, morphological, structural, optical and EC properties were characterised by using step profilometer, scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, ultraviolet-visible (UV-Vis) spectrophotometer and cyclic voltammetry (CV) and chronoamperometry (CA) measurements, respectively

Comparison of Light Trapping in Silicon Nanowire and Surface Textured Thin-Film Solar Cells

The optics of axial silicon nanowire solar cells is investigated and compared to silicon thin-film solar cells with textured contact layers. The quantum efficiency and short circuit current density are calculated taking a device geometry into account, which can be fabricated by using standard semiconductor processing. The solar cells with textured absorber and textured contact layers provide a gain of short circuit current density of 4.4 mA/cm2 and 6.1 mA/cm2 compared to a solar cell on a flat substrate, respectively. The influence of the device dimensions on the quantum efficiency and short circuit current density will be discussed

P-Type Characteristic of Nitrogen-Doped ZnO Films

Zinc oxide (ZnO) is a promising material for emerging electronic and photonic applications due to its wide direct band gap and large exciton binding energy. Despite on-going developments, the control of the conductivity type in ZnO films continues to be a challenge. Stable p-type ZnO is required in order to fabricate standalone ZnO-based devices. Nitrogen is considered as a promising candidate to produce a shallow acceptor level in ZnO, since it has similar radii and electrical structure to oxygen. In this experiment, we utilize the low cost sol–gel spin coating technique to fabricate nitrogen-doped ZnO (ZnO:N) films. All films show great optical transmittance above 80% in the visible region. ZnO:N film at 15 at.% doping concentration shows strong UV emission and exhibits low resistivity. A p–n homojunction device based on ZnO:N shows characteristic of a typical rectifying diode, with a turn-on voltage of approximately 1.2 V