JPE Editor in Chief Sean Shaheen outlines a vision for the journal.

Thanks to the reviewers who served JPE in 2020.

We numerically studied the effect of the geometric structure and Al component on the optical capture performance of gradient Al component Al_xGa_{1  −  x}N photocathodes. The effects of geometric parameters, such as base radius (R), wire-to-wire spacing, cone rate, and angle of incident light, on the optical response were systematically studied based on the finite element method. In the radial direction, we study the optical response of rectangular periodic structure and hexagonal periodic structure. Simulation results show that pencil nanostructure can achieve omnidirectional and broadband light absorption of Al_xGa_{1  −  x}N nanowires with hexagonal periodic structure. In addition, we used the Spicer three-step emission model to establish the photoemission efficiency of the Al_xGa_{1  −  x}N nanostructure. As a result, the photocathode achieves optimal quantum efficiency when the Al component is in the range of 0 to 0.75 and sublayer thickness of 240, 180, 120, and 60 nm.

Optical absorption of rectangular a-Si/c-Si solar cells is investigated. Each nanowire consists of a thin layer of a-Si, which surrounded by c-Si layers. The proposed structure has a very simple geometry compared with other nanowire solar cells, while its absorption rate is comparable to very complex structures. Periodic, semiperiodic, and multiple rectangular nanowires are used to achieve broadband absorption. In order to maximize the short-circuit current density of the proposed nanowire solar cells, particle swarm optimization algorithm has been performed. Irregularities have been observed to be one of the ways of absorbing broadband.

Filtering of the sub-band spectral radiation is an attractive technique to overcome the lower efficiencies of direct conversion thermophotovoltaic technology. The poor performance of these systems is due to the relatively small portion of the incident energy being above the bandgap of photovoltaic cell. To effectively filter the majority of the sub-bandgap radiation and re-employ it as regenerative heat, a viable solution is to design an efficient spectrally selective filter ideally matched to the photovoltaic cell’s bandgap. Here, we have explored a high contrast amorphous silicon grating on a quartz substrate. Quartz due to its inherent nature inhibits transmission of sub-band gap radiation in the infrared (IR) region (>4.75  μm), whereas gratings further filter radiation above 1.8  μm suitable for GaSb photovoltaic cell. The optimized filter is fabricated using direct write laser lithography, and optical characterization result shows that 72% of incident radiation in unconvertible region (>1.80  μm) is filtered and recycled. Further, the thermal characterization results of IR filter carried out using a ceramic heater has shown the drop in effective temperature from 1074.9 to 813.2 K in above bandgap region. This suppressed radiation has contributed to an absolute increase in source body temperature by 16.0 K resulting in increase in the above bandgap radiation available for thermophotovoltaic conversion. The proposed spectral filtering design can be tailored to solar cells of any bandgap and is scalable for employment in various thermophotovoltaic applications.

The optical properties of suspensions of P25 TiO₂ photocatalyst are calculated with particulate-aggregates-based light scattering model. The effects of structure, number of monomer, and particle radius of cluster on the absorption and scattering coefficients are analyzed. It is found that the radius of particle in clusters significantly affects their scattering capacity, and this effect could be attributed to the dielectric resonance of single particle and the cooperative scattering caused by coupling of electric dipoles of adjacent particles. Our work may promote the understanding of interaction between light and photocatalysts.

A fabrication of Sb₂S₃ layer as surface modification on pyramidal BiVO₄ film is realized to improve photoelectrochemical (PEC) performance of BiVO₄ photoanode. The Sb₂S₃-modified BiVO₄ film exhibits an increased photocurrent density of 1.1  mA  /  cm² at 1.23 V versus reversible hydrogen electrode and a negative shift of onset potential. Further, the negative shift of flat band potential demonstrates that the role of Sb₂S₃ surface modification is to suppress surface recombination, and thus increased surface separation and hole transfer efficiency are also achieved for the Sb₂S₃-modified BiVO₄ photoanode. Accordingly, the Sb₂S₃ surface modification enhances surface water oxidation kinetics for the BiVO₄ photoanode, resulting in improved PEC performance. These findings inspire further application of Sb₂S₃ into a PEC water splitting system.

A significant advancement in the Ce:Nd:YAG solar laser performance using a side-pumping configuration is reported. A solar laser head was composed of a double-stage semispherical lens and a trapezoidal-shaped pumping cavity, which coupled and redistributed the concentrated solar radiation from the focal zone of a parabolic mirror into a laser rod. The laser output performance of a 4.0-mm diameter, 35-mm length Ce:Nd:YAG laser rod was tested and compared with that from a Nd:YAG rod with the same dimensions. At an incoming solar power of 600 W, the Ce:Nd:YAG solar laser achieved 23.6-W  /  m² collection efficiency, 4.4% slope efficiency, and 2.8% solar-to-laser power conversion efficiency, which are 1.57, 1.47, and 1.56 times, respectively, higher than the ones obtained with the Nd:YAG rod. The Ce:Nd:YAG side-pumped solar laser has also 1.39 and 1.15 times more collection efficiency and solar-to-laser power conversion efficiency, respectively, than the previous record by Nd:YAG side-pumped solar laser. We demonstrate the great potential of the Ce:Nd:YAG ceramic rod as a gain medium for side-pumped solar lasers.