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In thermophotovoltaic (TPV) systems, it is crucial that the selective emitters can tailor emission spectrum to match the bandgap of photovoltaic (PV) cells and largely enhance the system efficiency. In this work, a metamaterial emitter based on the metal-insulator-metal (MIM) structure is proposed to obtain the high energy conversion efficiencies. The geometric parameters of MIM emitter have been investigated to obtain an excellent radiation spectrum of emitter composed of W and HfO₂. The excellent emission performance of MIM emitter is attributed to the excitation of surface plasmon polariton (SPP) and cavity resonance, and the structure of MIM emitter is insensitive for different polarization modes. The 21 material combinations of MIM emitters have been screened to obtain the optimal emitter matching GaSb and InGaAsSb cells. This work identifies the crucial role of structure and materials into the emitter of a TPV system. In the evaluation of MIM emitter and TPV System, when the operating temperature of emitter increases from 1400K to 2000K, the system efficiency of optimal W/HfO₂/W MIM emitter increases from 20.26% to 30.41%, while the output electric power increases from 3.59kW/m² to 42.48kW/m². The phenomenon indicates that the MIM emitter with the optimal material combinations and geometric parameters can significantly improve the matching degree with GaSb and InGaAsSb cells. Our results will be helpful to expand the optimization scope of metamaterial emitters in TPV systems.

Carbon films have been deposited on quartz and single-crystal silicon substrates by pulsed laser deposition technique. The soot for the target was obtained from burning camphor, a natural source. The effect of nitrogen (N) incorporation in camphoric carbon film is investigated. Optical gap for the undoped film is about 0.95 eV. The optical gap remains unchanged for low N content and decreases to about 0.7 eV. With higher N content, the optical gap increases. The resistivity of the carbon film increases with N content, initially and decreases with higher N content up till the film that is deposited at 30 mTorr. The results indicate successful doping for the film deposited at low nitrogen content. The J–V characteristics of N-incorporated carbon/silicon photovoltaic cells under illumination are observed to improve upon N-incorporation in the carbon layer.

The dye-sensitized solar cell using visible and near-infrared sensitization of nanocrystalline TiO₂ films by aluminium phthalocyanine, aluminium 2,9,16,23-tetraphenoxy-29H, 31H-phthalocyanine hydroxide (AlTPPc), was developed and its photoelectrochemical properties were investigated. The short-circuit photocurrent (I_SC) was 0.026 mA cm^-2, the open-circuit photovoltage (V_OC) was 186 mV, and the fill factor (FF) of solar cell using AlTPPc adsorbed on nanocrystalline TiO₂ film electrode was estimated to be 40.4%, respectively. By using AlTPPc adsorbed on nanocrystalline TiO₂ film electrode, photovoltage and photocurrent were higher compared with that of only nanocrystalline TiO₂ film electrode and were maintained under near-infrared irradiation. Thus, the solar cell using the near-infrared sensitization by AlTPPc adsorbed on nanocrystalline TiO₂ film electrode was developed.

The dye-sensitized solar cell (DSSC) using visible and near-infrared sensitization of nanocrystalline TiO₂ films using a series of four aluminum phthalocyanines was developed and its photoelectrochemical properties were investigated. By using aluminum 2,9,16,23-tetrakis(phenyl-thio)-29H,31H-phthalocyanine chloride adsorbed on a nanocrystalline TiO₂ film electrode, the I_SC, V_OC, FF, P_max and η values were largest compared with the other DSSCs using aluminum phthalocyanines. For all the DSSCs using aluminum phthalocyanines, IPCE values at near-infrared region (700 nm) are larger than those at visible region (500 nm). Thus, the DSSC using near-infrared sensitization of nanocrystalline TiO₂ film by aluminum phthalocyanines was developed.

π-Complex formation between porphyrins and their radical cations plays an important role in self-exchange electron transfer between neutral porphyrins and the radical cations, leading to negative activation enthalpies when the stabilization energy of the π-complex is larger than the activation energy for the intracomplex electron transfer in the π-complex. A number of porphyrin molecules are self-organized on three-dimensional gold nanoclusters to form monolayer-protected gold nanoclusters (MPCs) that act as an efficient photocatalyst for the uphill reduction of HV²⁺ by BNAH to produce 1-benzylnicotinamidinium ion (BNA⁺) and hexyl viologen radical cation (HV^·+). Such three-dimensional architectures of porphyrin MPCs with large surface area allow supramolecular π-complexation between MPCs and HV²⁺, resulting in fast electron transfer from the singlet excited state of porphyrin to HV²⁺ on MPCs. The π-π interaction is exploited to develop efficient photovoltaic devices consisting of porphyrin and fullerene assemblies which have an enhanced light-harvesting efficiency throughout the solar spectrum together with a highly efficient conversion of the harvested light into electrical energy.

We have newly constructed supramolecular photovoltaic cells using inclusion complexes of lithium-ion-encapsulated [60]fullerene (Li⁺@C₆₀) and cyclic porphyrin dimers (M-CPD_Py, M = H₄ and Ni₂). First, supramolecular inclusion complexes of Li⁺@C₆₀ and M-CPD_Py were prepared in MeCN/PhCN (3/1, v/v) by rapid injection method. The molecular aggregates with spherical nanoparticles demonstrated a broad absorption property in the visible region. The macroscopic structures were also estimated to be ca. 200 nm in diameter by transmission electron microscope (TEM) and dynamic light scattering (DLS) measurements. The photoelectrochemical solar cells composed of these assemblies on nanostructured SnO₂ electrode were fabricated by electrophoretic deposition method. The photoelectrochemical behavior of the nanostructured SnO₂ film of supramolecular nanoassemblies of Li⁺@C₆₀ and M-CPD_Py is significantly higher than those of the single component films (Li⁺@C₆₀ or M-CPD_Py) and supramolecular inclusion complexes of pristine C₆₀ and M-CPD_Py.