KEYWORDS: Thin films, Solar cells, Coating, Temperature metrology, Thin film coatings, Solar energy, Silicon, Refractive index, Photonics, Optical properties
The field of thermophotovoltaics offers a direct method to translate the heat generated as a byproduct of other standard energy generation techniques into usable electricity. This requires an emitted spectrum tailored to produce the maximum possible amount of light in a wavelength regime which is utilizable by a given photovoltaic cell. In this work, we investigate the efficiency of coating/substrate emitters using ~50 materials with melting points >2000C. We show combinations including oxide/refractory metal coating/substrate pairs which result in an FOM of >40% at 1800C, demonstrating their potential to greatly outperform currently available thermophotovoltaic devices.
Localized surface plasmon resonance (LSPR) shows great promise in optoelectronic devices, solar steam generation, and medical treatment owing to its strong enhancement of light-matter interactions. Herein, for the first time, 1D-2D metallic MWCNTs and HfTe2 van der Waals (vdW) heterostructure are used for demonstrating the LSPR to enhance the temperature of a solar absorber. The proposed vdW heterostructure is synthesized by a facile self-grown hydrothermal method and grown on top of a copper (Cu) foam. The HRTEM image and EDS spectrum confirm the formation of the vdW heterostructure on the Cu foam. The synergic effect of Te-based TMD with MWCNT provides a broadband absorbance of approximately 92% weighted by the standard air mass 1.5 global solar spectrum and takes full advantage of LSPR to confine heat in a small area. Moreover, the ultrathin nature of MWCNT endows them with the super permeability of water vapor. The solar-driven steam generation performance of the prepared vdW heterostructure demonstrates an excellent evaporation efficiency of 87.43% and an increment of the surface temperature to 79.8 °C in less than 20 mins under 1 kWm–2 solar illumination. Therefore, the proposed vdW heterostructure can be realized in high-temperature steam generation applications.
Two-dimensional (2D) materials are getting a lot of attention in the nonlinear optics research due to their excellent structural characteristics and nonlinear effects. Here, the layered dependent second harmonic generation (SHG) of 2D-gallium sulfide (GaS) nanosheets are demonstrated for the first time. According to the obtained findings, SHG signal was identified exclusively for the odd layer GaS-nanosheets due to the existence of broken inversion symmetry. The even layer, on the other hand, generated no SHG signal due to its centrosymmetric structure. Moreover, the layered dependent damaged threshold of the prepared sample is also discussed here.
Photon management of perovskite solar cells (PSCs) is studied by the use of nanohole front contact, which allows improving the JSC of the PSC by providing an improved light incoupling. The front contact integrated with spherical nanocone shaped holes represent a refractive index grating allowing for light incoupling approaching unity while minimizing reflection losses. Besides, the front contact has a comparable refractive index (n~2.5) with the perovskite absorber, which minimizes the front reflections in PSC. Optics and optimization of front contact and solar cell are investigated by three-dimensional (3D) finite-difference time-domain (FDTD) simulations whereas finite element method simulations are used to study the electrical response of the device. Investigations reveal a maximum light incoupling enhancement of 10~12% for the optimized PSC, leading to 10 to 27% JSC enhancement with respect to the planar reference PSC.
Image sensing technology has a great impact on our daily life as well as the entire society, such as health, safety and security, communication systems, and entertainment. The conventional optical color sensors consist of side by side arranged optical filters for three basic colors (blue, green, and red). Hence, the efficiency of such optical color sensors is limited by only 33%. In this study, a vertically stacked color sensor is investigated with perovskite alloys, which has the potential to provide the efficiency approaching 100%. The proposed optical sensor will not be limited by color Moire error or color aliasing. Perovskite materials with suitable bandgaps are determined by applying the energy shifting model and the optical constants are used for further investigations. Quantum efficiencies and spectral responsivities of the described color sensors are investigated by three-dimensional electromagnetic simulations. Investigated spectral sensitivities are further analyzed for the
The energy conversion efficiency of perovskite solar cells can be boosted by enhancing the short-circuit current density, where efficient photon management allows realizing a high short-circuit current density. The efficient photon management relies mostly on the solar cell surface, hence, the front contact of the device. The front contact must fulfil some basic requirements so that both lateral charge transport and light incoupling can be achieved efficiently by lowering the optical losses. In this study, we utilized metal oxide films as a potential charge transport material and front contact, which allows achieving efficient photon management in perovskite solar cells. In the current study, a planar perovskite solar cell was fabricated experimentally, where nickel oxide hole transport layer is prepared by using electron beam deposition at a low temperature. Necessary material characterizations were performed to ensure the high-quality films. Spectroscopic ellipsometry measurements were carried out to extract the complex refractive index of the deposited films, which is used to study the optics of perovskite solar cells. Finite-difference time-domain optical simulations were used to investigate the optics and optimize the perovskite solar cells. Simulation results give a very good agreement with experimental results. Finally, an optimized perovskite solar cell structure will be proposed which can enhance the short-circuit current density and energy conversion efficiency by 20% and >25%, respectively. The optimized device design can be further applied to the implementation of perovskite/silicon tandem solar cells. Detail discussion of the proposed structure will be provided to attain effective photon management for perovskite solar cells.
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