Drawing on our reported light absorption enhancement strategy of planar meta-surface employed in solar cells, we extend it to photo-electrocatalytic water splitting and develop a one-dimensional model for this photocatalytic planar meta-surface. This model enables accurate calculations of the photocurrent density as a function of applied bias voltage; the simulation results agree well with experimental data in the literature. The underlying mechanism responsible for the superior photocatalytic performance of the planar meta-surface is elucidated by the comparison of its photo-carrier distributions to a conventional micron-scale film photo-electrode. Using a hematite planar meta-surface photo-anode as a representative case, the effects of carrier transport behaviors and key physical parameters on water splitting performance are systematically analyzed. The findings demonstrate that the photo-anode with optimized parameters can achieve significant enhancement in photocurrent and reduction in onset potential, offering theoretical insights and practical guidance for efficient solar-driven water splitting.
Photothermal-assisted photocatalysis, which couples localized thermal energy with photogenerated charge carriers to overcome thermodynamic and kinetic limitations, has emerged as an effective strategy for solar-driven CO2 reduction. Herein, nanoflower-like NiO/ZnO p-n heterojunction spheres were rationally constructed via a simple hydrothermal calcination method to achieve efficient concentrated photothermal-assisted CO2 reduction. The unique nanoflower morphology provides abundant interfacial contact between NiO and ZnO, while the formation of the p-n heterojunction establishes an internal electric field that suppresses electron-hole recombination. Under concentrated irradiation (4.31 W.cm(-2)), the photothermal coupling effect reduces the apparent activation energy and enables the NiO/ZnO photocatalyst to deliver CO and CH4 production rates of 51.78 and 15.96 mu mol.g(-1).h(-1), which are 7.92 and 9.61 times higher, respectively, than those obtained under nonconcentrated illumination. Photoelectrochemical measurements and in situ DRIFTS further reveal that the built-in electric field facilitates directional charge transfer from ZnO to NiO, thereby promoting CO2 adsorption and activation. We demonstrate an efficient photothermal-coupling strategy to construct high-performance catalysts for artificial photosynthesis and solar-to-fuel conversion.
We compare the capabilities of external and internal sensitizers in solar laser systems through numerical simulations. Three lasing media were studied: Nd:YAG, Nd:YAG with alexandrite as an external sensitizer, and Cr:Nd:YAG with Cr3+ ions as internal sensitizers. The Nd:YAG + alexandrite system showed a 1.38-fold efficiency gain over Nd:YAG without sensitizer, while Cr:Nd:YAG achieved a 1.34-fold improvement due to both radiative and nonradiative transfer mechanisms. Thermal analysis revealed that Cr:Nd:YAG becomes inoperative at input powers above 2.3 kW, whereas Nd:YAG and Nd:YAG + alexandrite remained stable up to 2.9 kW. It was shown that configurations based on external sensitization, in particular the Nd:YAG + alexandrite system, can provide both increased efficiency and excellent thermal stability, which offers clear advantages for high-power and long-term operation of solar lasers.
For wearable electronics applications, organic photovoltaic (OPV) cells are good candidates as sources of renewable energy. Many efforts have been devoted to increasing energy conversion efficiency in OPV cells, and improvement in light retention has been one of the main research directions. Within this context, our group recently proposed an OPV cell structure with a hemispherical-shell-shaped (HSS) active layer and discovered that it has high potential for substantial enhancement in absorption performance. As a continuation of the study, this paper reports an in-depth investigation of the proposed device, examining the effects of several design parameters on its absorption performance. Using finite element analysis, it is found that the absorption performance depends on the periodicity type, and that a hexagonal type results in higher absorption than a square one due to its closer shape resemblance to a circular cross-section. The absorption performance is also affected by a contact angle, i.e., the angle made between a sphere and a flat part of the structure. It is learned that the average integrated absorption generally increases along with the contact angle, which saturates at around 80 deg of contact angle. Lastly, the effects of a cell period are studied, and it turns out that the average integrated absorption decreases as the period increases. It is also observed that at high incidence angles (>similar to 75 deg ), an array with a shorter period results in lower absorption than one with a longer period owing to a partial obstruction issue. All of these results support the understanding that the primary contribution of absorption enhancement in the proposed HSS structure comes from improved light retention rather than from a simple advantage in active layer volume. It is envisaged that these study outcomes will provide important guidelines in the design of HSS OPV cells.
It has become a trend for the windows of modern buildings to be upgraded to smart windows with building-integrated photovoltaics (BIPVs). Smart windows are generally only used as outdoor photovoltaics to collect sunlight and generate electricity but are rarely used directly as indoor photovoltaics. We design a smart window with a sandwich structure, using a sandwiched a-Si bifacial semitransparent photovoltaic (BSTPV) cell to achieve double-sided collection and generation of indoor and outdoor light. The ethylene vinyl acetate (EVA) material that encapsulates the a-Si BSTPV cell is respectively doped with 0.9% yttrium aluminum garnet (YAG):Ce3+ phosphors and 0.8%YAG:Eu3+ phosphors, and its spectral down-shifting function is used to optimize the light source spectra, improve the spectral response of the a-Si BSTPV cell, and increase the conversion efficiency (PCE). Test results show that the PCE is relatively improved by no less than 5%. We expected to find application prospects for phosphor-in-EVA and further promote the development of BIPVs.
