Guest editors Zakya Kafafi and Mónica Lira-Cantú introduce the Special Section Celebrating Women in Renewable Energy (WiRE).

Transparent conductive materials (TCMs) with high p-type conductivity and broadband transparency have remained elusive for years. Despite decades of research, no p-type material has yet been found to match the performance of n-type TCMs. If developed, the high-performance p-type TCMs would lead to significant advances in a wide range of technologies, including thin-film transistors, transparent electronics, flat screen displays, and photovoltaics. Recent insights from high-throughput computational screening have defined design principles for identifying candidate materials with low hole effective mass, also known as disperse valence band materials. Particularly, materials with mixed-anion chemistry and nonoxide materials have received attention as being promising next-generation p-type TCMs. However, experimental demonstrations of these compounds are scarce compared to the computational output. One reason for this gap is the experimental difficulty of safely and controllably sourcing elements, such as sulfur, phosphorous, and iodine for depositing these materials in thin-film form. Another important obstacle to experimental realization is air stability or stability with respect to formation of the competing oxide phases. We summarize experimental demonstrations of disperse valence band materials, including synthesis strategies and common experimental challenges. We end by outlining recommendations for synthesizing p-type TCMs still absent from the literature and highlight remaining experimental barriers to be overcome.

A new generation of anode interlayers (AILs) has been introduced in recent years for improving the efficiency and stability of organic solar cell (OSC) devices. Electrode interlayer modification is a simple and effective way of enhancing OSC device performance. We used poly(vinyl pyrrolidone) (PVP) as an AIL modifier to alter molybdenum trioxide (MoO₃) and vanadium pentoxide (V₂O₅) AILs in OSC devices and compared them with pure metal oxide AILs. Using this modification, average power conversion efficiencies were raised from 5.2  %    ±  0.4  %   to 6.0  %    ±  0.3  %   for OSCs with MoO₃-based AILs, and from 6.2  %    ±  0.1  %   to 6.8  %    ±  0.3  %   for OSCs with V₂O₅-based AILs. Moreover, the PVP-metal oxide AILs also improved the overall device quality, producing a nanotextured morphology with good optical properties and favorable chemical composition. Beneficial wetting properties for interfacial adhesion between anode and active layer are observed using contact angle measurements. Overall, devices with PVP-modified metal oxide AILs showed promising results with greater device stability compared to pure metal oxide AIL-based OSC devices.

A photovoltaic (PV) panel operating in partial shading condition results in lowering its power efficiency. In a worst-case scenario, it can create a hotspot that can eventually cause a fire hazard. To address this issue, bypass diodes are connected across a group of PV cells having series-parallel (SP) configuration. Owing to the placement bypass diodes in the PV panel, it can circumvent unshaded PV cells. Hence, topologies such as total cross-tied (TCT), bridge link (BL), and honeycomb (HC) for PV panels are proposed besides SP to reduce the effect of partial shading. Each configuration demonstrated advantages over SP topology. However, many of these configurations lack a mechanism to isolate PV cells that are affected due to the hotspot. Recently developed complementary metal oxide semiconductor (CMOS)-embedded PV panel has been shown to offer many other benefits besides effectively dealing with shading conditions. We are comparing the performance of CMOS-embedded PV panel under various partial shading conditions with PV panel with fixed configuration topologies, such as SP, TCT, BL, and HC. SPICE-based equivalent PV modeling technique is used in this research to compare the maximum power generated in different topologies under changing partial shading conditions. Results show that CMOS-embedded PV panels are more efficient in coping with partial shading conditions compared to any other contemporary fixed topologies.

The luminescent coupling effect in a multijunction solar cell is known to help achieve current matching among subcells through carrier redistribution. We demonstrate the carrier redistribution in III-V multijunction solar cell devices using a moisture-resistant, all-inorganic perovskite quantum dot (PQD) film. This hydrophobic PQD film was applied on a full III-V multijunction solar cell device. This successfully demonstrated current redistribution vertically, shown by the increased current collection in the lower bandgap subcells, and laterally, as observed from improved current collection homogeneity in the lower bandgap subcell adjacent to the higher bandgap subcell where the luminescence originated.

Co₃O₄ nanoparticles were synthesized by a green synthesis method using bread fungus and cobalt nitrate hexahydrate as the precursors. The effects of the calcination temperature on the structure and properties of nanoparticles, and the ambient temperature on the photocatalytic reaction are discussed. The cubic structure of Co₃O₄ nanoparticles was obtained, and the grain size was between 14 and 19 nm at different calcination temperatures. Co₃O₄ calcined at 500°C shows good photocatalytic performance. Without adding any sacrificial agent and cocatalyst, the amount of hydrogen and oxygen released in 5 h were 259.4 and 135.7  μmolg^−  1, respectively. The results show that, with the increase of ambient temperature, the evolution rate of hydrogen and oxygen is accelerated, and the atomic ratio of hydrogen to oxygen is close to 2:1. In addition, the Co₃O₄ photocatalyst has good stability. Our study provides an environmentally friendly, low-cost, and efficient method for the preparation of cobalt oxide photocatalysts with excellent performance.

When a single spot in a planar luminescent waveguide is excited, some photoluminescence photons that are trapped inside reach its edge. Considering the photon losses due to leakage from its top and bottom surfaces and self-absorption during wave-guiding, the probability of collecting photons at its edge is expressed as a function of the coordinates of the excited spot for polygonal and curved waveguides. The emission is assumed to be isotropic, and scattering and re-emission events are neglected for simplicity. This model might be useful for predicting the performance of luminescent waveguides with various shapes under non-uniform illumination.

Near-field electroluminescent refrigerators (NFERs) have potential applications in thermal management. The input electricity can manipulate the photons’ electrochemical potential to realize heat transfer from cold side to hot side. However, the coupled properties and the overall optimum performances of the NFER driven by actual power sources have not been studied. A model of solar cell powered NFER is conceptually proposed and optimally designed. The electrical coupling characteristics between the solar cell and the NFER are discussed. The operating region of the NFER’s input voltage is provided. The structure and the electrical parameters are optimized to obtain the maximum efficiency. The effects of the vacuum gap, the emitter’s thickness, and the solar irradiance on the optimum performances are analyzed. Making trade-offs between the efficiency and cooling heat flow rate, the optimum region of solar irradiance is determined. The proposed model and the parametric optimal analysis can provide a route for solar-driven refrigerators.

Grätzel solar cells are reported in a transparent conducting oxide-less (TCO-less) back-contact dye-sensitized solar cell (BC-DSC) architecture using a stainless steel mesh-protected working electrode along with nanoporous TiO₂ semiconductor and metal-free D205 dye. Liquid electrolytes play a significant role for the dye regeneration in the working operation of TCO-less BC-DSCs; therefore, we report the effectiveness of two different commonly utilized electrolytes (iodine- and cobalt-based redox shuttles) for the construction and performance of TCO-less dye-sensitized solar cells (DSCs). Differential performance of DSCs thus fabricated was interpreted utilizing impedance spectral and lifetime analysis. It was found that although utilization of cobalt bipyridyl complex-based electrolyte was able to harvest higher photons in the lower wavelength region (330 to 430 nm) as compared to its iodine electrolyte counterparts, hampered dye regeneration due to reduced driving force and slower ion diffusion in combination with higher charge transport resistance at TiO₂  /  dye  /  electrolyte was responsible for relatively hampered photovoltaic performance at peak absorption.

The characteristics of silicon nanowires (SiNWs) with surface roughness are reported and analyzed for solar cell (SC) applications. The SiNWs are fabricated using a metal-assisted chemical etching process. The effects of the etching time and reaction temperature on the surface roughness and the performance of the SiNWs are investigated. Further, the optical and electrical characteristics of the roughed NW SC are numerically studied and optimized using 3D finite difference time domain and finite element analysis, respectively. The numerically optimized SiNWs with surface roughness offer high optical ultimate efficiency (η) of 32.51% with an enhancement of 15.98% over the smoothed SiNW. This is due to the surface textures of the nanowires which produce multiple light scattering between the NWs’ walls. This will enhance the optical path length through the NW and enrich its light absorption. The doping level of the surface roughness of NWs with p-type/intrinsic/n-type (p-i-n) axial configurations is also simulated to compute the optoelectronic performance of the suggested design. The p-i-n axial doped design offers a power conversion efficiency of 14.92%, whereas the conventional NWs have a power conversion efficiency of 13.16%.

We report the effect of cyclodextrin (CD) cavity size on the photovoltaic performance of dye-sensitized solar cells (DSSCs) containing inclusion complexes of tris(2,2′-bipyridyl)ruthenium(II) ([Ru(bpy)3]^2  +) in various CDs ([Ru(bpy)3]^2  +  /  CD). The incident photon-to-current conversion efficiency (IPCE) of the [Ru(bpy)3]^2  +-containing DSSC at 460 nm was calculated to be 8.1%, and this value was enhanced by the formation of [Ru(bpy)3]^2  +  /  CD. The IPCE values of [Ru(bpy)3]^2  +  /  α-CD-containing, [Ru(bpy)3]^2  +  /  β-CD-containing, and [Ru(bpy)3]^2  +  /  γ-CD-containing DSSCs were 8.8%, 8.9%, and 11.2%, respectively. It was concluded that the difference of IPCE values of [Ru(bpy)3]^2  +  /  CD-containing DSSCs were caused by the CD cavity size, which affected the host–guest interaction between [Ru(bpy)3]^2  + and the CD. These findings indicated that the cavity size of γ-CD is suitable to promote the photovoltaic conversion of DSSCs containing an unanchored photosensitizing dye with nonplanar molecular structure such as ruthenium(II) polypyridine and diimine copper(I) complexes.

Numerical model was developed to analyze photovoltaic parameters according to electronic properties of InGaN/GaN multiple quantum well solar cell (MQWSC) under hydrostatic pressure. Finite difference method was used to acquire energy eigenvalues and their corresponding eigenfunctions of InGaN/GaN MQWSC and hole eigenstates were calculated using a 6  ×  6 k.p method under an applied hydrostatic pressure. Our results show that depth of quantum wells, bandgaps, band offset, electron, and hole density increase with the increase in the hydrostatic pressure. Also as pressure was increased, electron and hole wave functions had less overlap, amplitude of absorption coefficient was increased, and binding energy of excitons was decreased. A change in pressure of up to 10 GPa caused absorption coefficient’s peaks of light and heavy holes to shift to low wavelengths of up to 32 nm, along with decreased current density of short circuit, increased open circuit voltage, and enhanced efficiency of InGaN/GaN MQWSC.