Novel approach to optimize quantum dot (QD) materials for specific optoelectronic applications is based on engineering of nanoscale potential profile, which is created by charged QDs. The nanoscale barriers prevent capture of photocarriers and drastically increase the photoelectron lifetime, which in turn strongly improves the photoconductive gain, responsivity, and sensitivity of photodetectors and decreases the nonradiative recombination losses of photovoltaic devices. QD charging may be created by various types of selective doping. To investigate effects of selective doping, we model, fabricated, and characterized AlGaAs/InAs QD structures with n-doping of QD layers, doping of interdot layers, and bipolar doping, which combines p-doping of QD layers with strong n-doping of the interdot space. We have measured spectral characteristics of photoresponse, photocurrent and dark current. The experimental data show that providing the same electron population of QDs, the bipolar doping creates the most contrasting nanoscale profile with the highest barriers around dots.

We show that by subsequent sensitization of nanostructured ZnO photoanodes with N-719 and Rose Bengal dyes an improvement or worsening of the cell efficiency may be obtained, relating to photoanodes sensitized with N-719 dye only (J SC = 2.97 mA/cm2, V OC = 0.68 V, η = 0.99%) depending on the order in which the dyes are applied. We observe that for the case when the N-719 dye is followed by Rose Bengal an increase in efficiency, short circuit current and open circuit voltage is observed (J SC = 3.95 mA/cm2, V OC = 0.71 V, η = 1.26%), which we relate to the cascade band alignment of the ZnO and the dyes. In the case when Rose Bengal is first on ZnO followed by N-719, a lowering of all parameters is observed (J SC = 2.86 mA/cm2, V OC = 0.64 V, η = 0.94%) due to the trap band alignment. Electrochemical impedance spectroscopy measurements and modelling confirmed this theory showing longer electron lifetimes in the photoanode for the cascade band alignment, enhancing electron-hole separation, than for the trap alignment, facilitating electron-hole recombination.

SiO2-MgF2/TiO2 double-layer films with antireflective, self-cleaning and adherent properties were prepared by spin-coating SiO2-MgF2 and TiO2 sol on glass substrate successively and subsequently being calcined at 250°C. The optical and structural properties of films have been investigated by visible spectrophotometer and field emission scanning electron microscope, respectively. At the same time, self-cleaning property generated from superhydrophilicity and photocatalysis was obtained. The results indicated that the as-prepared SiO2-MgF2/TiO2 double-layer films show a maximum increase in transmittance near 520 nm wavelength of 2.8% and photocatalytic property with the R value of 4.7(JIS R 1703–2).It has been demonstrated that high transmittance, self-cleaning and adherent composite has been obtained by a simple sol–gel route presenting good potential to be applied on photovoltaics systems.

This paper will propose methods to use leaf vasculature formations to advance a material to act as an infrared block. The research shows the use of microfluidics based flows to direct the structural assembly of a polymer into a thermally functional material. To manage IR radiation stop-band to lower a polymer device phase transition temperature. This paper will determine this functionality by hierarchical multi microchannel network scaling, to regulate laminar flow rate by analysis as a resistor circuit.

Nature uses vasculature formations to modulate irradiance absorption by laminar fluidic flow, for dehydration and autonomous self-healing surfaces as a photoactive system. This paper will focus specifically on pressure drop characterization, as a method of regulating fluidic flow. This approach will ultimately lead to desired morphology, in a functional material to enhance its ability to capture and store energy. The research demonstrates a resistor conduit network can define flow target resistance, that is determined by iterative procedure and validated by CFD. This algorithm approach, which generates multi microchannel optimization, is achieved through pressure equalization in diminishing flow pressure variation. This is functionality significant in achieving a flow parabolic profile, for a fully developed flow rate within conduit networks. Using precise hydrodynamics is the mechanism for thermal material characterization to act as a switchable IR absorber. This absorber uses switching of water flow as a thermal switching medium to regulate heat transport flow. The paper will define a microfluidic network as a resistor to enhance the visible transmission and solar modulation properties by microfluidics for transition temperature decrease.

Over the last 30 years organic carbon nanotube-yarn (CNTY) based dye-sensitized solar cells (DSSCs) have received considerable interest. CNTY based DSSCs have become a main focus of alternative energy source research. CNTY based PV cells have an advantage over cells based on non-flexible substrates, such as fluorine doped tin oxide glass; as a foundation for dye-sensitized solar cells, CNTYs are superior due to their low-cost, environmental sustainability, high mechanical integrity, and numerous beneficial practical applications. CNTY based DSSCs also have additional advantages because of their low electrical resistance, excellent electrocatalytic activity, and ultra-high mechanical integrity. Additionally, quantum dots and polymers have shown great promise for photovoltalic application due to their tunable bandgap and wide photon absorption range. This research explores the barrier characteristics associated with new absorbing photovoltaic materials that promote electron/hole pair separation and transportation. Utilizing the hybrid bandgap structures of quantum dots and polymers as well as the flexibility of CNTY, we reported a 3D flexible DSSC with an efficiency of 2.9%.

In this work, we describe the combination of hydrothermal and atomic layer deposition (ALD) for growing low-resistivity ZnO polycrystalline continuous films. The effect of the thickness of ALD seed layers on the morphology of the hydrothermal ZnO films was studied. It was shown that ZnO films hydrothermally deposited on very thin seed layer consist of separate nanorods but in the case of 20 nm seed layer ZnO films transform to uniform continuous layers comprising of closely packed vertically aligned crystallites. Photoluminescence spectra were shown to exhibit broad band behavior in the visible range, corresponding to radiative recombination processes via oxygen defects of ZnO crystalline lattice, and narrow band in the UV region, associated with band-to-band recombination processes. It was shown that the resistivity of the obtained ZnO films is decreased gradually with the increase of ZnO films thickness and determined by the presence of crystal lattice defects in the seed layer.

In this work, we have demonstrated the light concentration from zero-contrast gratings (ZCG) subwavelength structures and compared the light concentration properties of previously proposed high-contrast gratings (HCG) to the ZCG micro concentrating lenses. To address the challenges of potential HCG fabrication, the difference between ZCG and HCG micro lenses is investigated numerically and found both of these subwavelength grating structures have similar light concentration characteristics. To gain deeper understanding of this phenomenon, we have explored the light concentration formation process and discussed the concentration mechanism in detail. Our work will be promising to provide a new ZCG micro lens potentially with easier and more controllable fabrication and could be utilized for various integrated nanophotonics applications, from optical cavities, read/write heads and concentrating photovoltaics.

Electron transfer in molecular wires are of fundamental importance for a range of optoelectronic applications. The impact of electronic coherence and ionic vibrations on transmittance are of great importance to determine the mechanisms, and subsequently the type of wires that are most promising for applications. In this work, we use the real-time formulation of time-dependent density functional theory to study electron transfer through oligo-p-phenylenevinylene (OPV) and the recently synthesized carbon bridged counterpart (COPV). A system prototypical of organic photovoltaics is setup by bridging a porphyrin-fullerene dyad, allowing a photo-excited electron to flow between the Zn-porphyrin (ZnP) chromophore and the C60 electron acceptor through the molecular wire. The excited state is described using the fully self-consistent ∆-SCF method. The state is then propagated in time using the real-time TD-DFT scheme, while describing ionic vibrations with classical nuclei. The charge transferred between porphyrin and C60 is calculated and correlated with the velocity autocorrelation functions of the ions. This provides a microscopic insight to vibrational and tunneling contributions to electron transport in linked porphyrin-fullerene dyads. We elaborate on important details in describing the excited state and trajectory sampling.