Complex three-dimensional (3-D) super structural TiO2 architectures with controlled shape and size were synthesized by a facile hydrothermal synthesis route by using titanium tetrachloride (TiCl4) as the metal precursor and hydrochloric acid (HCl)/ammonium chloride (NH4Cl) as the mineralizer/structure directing agent. Several interesting hierarchical architectures like: (i) nanoparticles assembled spheres (NPAS), (ii) nanowires assembled spheres (NWAS), (iii) nanorods assembled spheres (NRAS), and (iv) nanosheets assembled spheres (NSAS) were achieved by the controlled variation of crystal structure modifier. The synthesized materials were characterised in detail by different analytical techniques and the findings are consistent. To demonstrate the superior performances of the as prepared materials the photocatalytic and photo-voltaic performances were investigated. The results demonstrate that these synthesized materials exhibits enhanced photocatalytic activity (efficiency is ∼ 91%) towards the degradation of RhB and as a photoanode in DSSCs the maximum energy conversion efficiency is ∼5%, attributed primarily to the unique hierarchical mesoporous structure of the TiO2 architectures.

Solar thermophotovoltaic (STPV) systems convert sunlight into electricity via thermal radiation. The efficiency of this process depends critically on both the selective absorber and the selective emitter, which are controlled by both the materials and the photonic design. For high concentration solar TPV applications, 2D photonic crystals (PhCs) made of refractory metals such as tungsten have demonstrated promising results. For even higher performance, we propose two photonic crystal-based designs to both collect solar heat and reradiate above-gap photons. First, a PhC selective structure (IPSS), which combines 2D photonic crystals and filters into a single device. Second, an Er-Yb-Tm co-doped fused silica coated with a 17-bilayer structure also offers significant selectivity with greater ease of fabrication. Finite difference time domain (FDTD) and rigorous coupled wave analysis (RCWA) simulations show that both can significantly suppress sub-bandgap photons. This increases sunlight-to-electricity conversion for photonic crystal-based emitters above 24.3% at 100 suns concentration or 27% at 1000 suns concentration using a Ga0.42In0.58As PV diode with a bandgap of 0.7 eV (nearly lattice-matched to InP).

Iron oxide nanotubes (NTs) and zinc doped iron oxide NTs were prepared by sol-gel method. Obtained NTs have spinel structure represented by ZnδFe3-δO4. Iron oxide NTs indicated a spectral sensitivity maximum at the wavelength of 500-550 nm and a long tail toward red light. These features were explained by a typical bandgap of iron oxide NTs to be ∼2.3 eV and bandgap narrowing for a small diameter NT. Organometal perovskite solar cell was constructed by using these NTs and evaluated by measuring the spectral sensitivity between the wavelength of 390 and 710 nm. For the present perovskite solar cell, drastic increase of the spectral sensitivity was obtained when we adjusted penetration depth of organometal perovskite into the porous layer of NTs. However, deep penetration worsened the spectral sensitivity. A similar trend was obtained for the cell using Zn doped iron oxide NTs, but the magnitude of incident power conversion efficiency (IPCE) became almost a half. This was explained by worsening the electrical conductivity, even the bandgap became narrower by Zn dope.

Silicon heterojunction (Si-HJT) solar cells are one of the most efficient silicon-based solar cells, due largely to their high open-circuit voltages. For the transparent conductive oxide (TCO) layers, there is a design trade-off between their conductance and their parasitic light absorption, and this trade-off can be a performance-limiting factor for Si-HJT solar cells. It has been demonstrated that silver nanowire (AgNW) networks with superior optical and electrical performances, can complement TCOs. To evaluate the performance of AgNW-TCO hybrid electrodes for Si-HJT cells, it is beneficial to numerically simulate and optimize the optical and electrical performances of the entire device. However, the dimensions of the AgNWs are massively different to the dimensions of the other components of the cells, making individual modeling methods incapable. In this paper, we use an angular matrix framework (AMF) to resolve the challenge, where matrices are used to describe the transition of the angular distribution of the light when it is reflected or transmitted at the interface, or absorbed in the bulk. These matrices pass optical information between nanoscale and microscale components of the cell structure. Using AMF, we calculated the optical properties of the devices, and demonstrated that the AgNW-TCO electrode has advantages over a TCO electrode. Guidance on how the optimization of the composite electrode can be achieved was provided.

We here report the fabrication of high-quality nanostructured electrodes based on surfactant-capped ITO colloidal nanocrystals and their implementation in self-powered bi-functional smart devices which are simultaneously capable of generating electric energy as a photovoltaic system as well as of controlling the intensity of incoming thermal radiation by means of a smart variation of their optical transmittance. A reversible modulation of the solar transmittance in the NIR range higher than 60% has been experimentally demonstrated.

It is known that photonic crystals can be used to suppress spontaneous emission. This property of photonic crystals has been investigated for suppressing and decreasing the propagation of photons within loss cones in fluorescent collectors. Fluorescent collectors can concentrate light onto solar cells by trapping fluorescence through total internal reflection. In an ideal fluorescent collector the major obstacle to efficient photon transport is the loss of photons through the top and bottom escape cones. One possible method to decrease this loss and improve the efficiency of these devices is to fabricate one-dimensional photonic crystals doped with fluorescent molecules. If these photonic crystals are tuned to exhibit a photonic band gap in the escape cone directions and at the emission frequencies of the fluorescent molecules, a suppression of the escape cone emission and an enhancement of the edge emission is expected. In this paper, we detail the fabrication of a one dimensional integrated photonic collector and show the suppression of the escape cone emission. This suppression of the escape cone will be shown to correspond to the photonic band gap and the modifications to the edge emission will be shown to correspond well with so called Fabry Perot modes. The control of emission inside fluorescent collectors opens up a number of additional possibilities for efficiency enhancements that will also be discussed.

Atomically thin transition-metal dichalcogenides (TMD) hold promise for making ultrathin-film photovoltaic devices with a combination of excellent photo-absorption and mechanical flexibility. However, reported absorption for photovoltaic cells based on TMD materials is still just a few percent of the incident light due to their sub-wavelength thickness leading to low cell efficiencies. Here we discuss that taking advantage of the mechanical flexibility of two dimensional (2D) materials by rolling their Van der Waal heterostructures such as molybdenum disulfide (MoS2)/graphene (Gr)/hexagonal boron nitride (hBN) to a spiral solar cell, leads to strong light matter interaction allowing for solar absorptions up to 90%. The optical absorption of a 1 µm-long hetero-material spiral cell consisting of the aforementioned hetero stacks is about 50% stronger compared to a planar MoS2 cell of the same thickness; although the volumetric absorbing material ratio is only 6%. We anticipate these results to provide guidance for photonic structures that take advantage of the unique properties of 2D materials in solar energy conversion applications.

The production of hydrogen by photocatalytic water splitting is a potentially clean and renewable source for hydrogen fuel. Cadmium chalcogenides are attractive photocatalysts because they have the potential to convert water into hydrogen and oxygen using photons in the visible spectrum. Cadmium sulfide rods with embedded cadmium selenide quantum dots (CdSe@CdS) are particularly attractive because of their high molar absorptivity in the UV-blue spectral region, and their energy bands can be tuned; however, two crucial drawbacks hinder the implementation of these materials in wide spread use: poor charge transfer and photochemical instability.

Utilizing photochemical deposition of co-catalysts onto CdSe@CdS substrates we can address each of these weaknesses. We report how novel co-catalyst morphologies can greatly increase efficiency for the water reduction half-reaction. We also report photostability for CdSe@CdS under high intensity 455nm light (a wavelength at which photocatalytic water splitting by CdSe@CdS is possible) by growing metal oxide co-catalysts on the surface of our rods.