This work examines a tandem module design with GaInP2 mechanically stacked on top of crystalline Si, using a detailed photovoltaic (PV) system model to simulate four-terminal (4T) unconstrained and two-terminal voltage-matched (2T VM) parallel architectures. Module-level power electronics is proposed for the 2T VM module design to enhance its performance over the breadth of temperatures experienced by a typical PV installation. Annual, hourly simulations of various scenarios indicate that this design can reduce annual energy losses to ∼0.5% relative to the 4T module configuration. Consideration is given to both performance and practical design for building or ground mount installations, emphasizing compatibility with existing standard Si modules.

GaAsP self-assisted core–shell p-i-n nanowires were grown on Si solar cells. The resulting tandem cell exhibited an enhanced Voc of 1.16 V, increasing from 0.54 V for the Si cell alone. Nevertheless, the efficiency of the tandem cell was only 3.51% as compared with 9.33% for the Si cell due to a current-limiting short-circuit current density from the nanowires. Further improvement in device performance can be realized by improving the nanowire open-circuit voltage and short-circuit current, related to doping of the nanowires.

The coupling of resonant modes between two surfaces is important in near-field heat transfer and near-field thermophotovoltaic (TPV) systems. Recently, coupled-mode theory (CMT) has been developed for the analysis and optimal design of TPV systems. We use CMT to analyze the “emitter-vacuum-PV cell” configuration and quantitatively show how the emitter of a nanostructure can drastically improve the near-field TPV device performance. The key feature of the nanostructure is the additional geometry-induced resonant mode, whose energy is lower than the original surface plasmon polariton resonant frequency and much closer to the bandgap of the PV cell. Specifically, we show that, with a simple grating structure, the generated power density of a TPV cell is increased from 13 to 34  W/cm2 when the PV cell is fixed at 300 K and the emitter is at 1000 K. The increase is over 20 times higher when both planar and grating emitters are at a lower temperature of 500 K.

It has been demonstrated experimentally that the presence of metallic nanoparticles (MNPs) in the active layer assists in improving the power conversion efficiency of organic solar cells (OSCs), due to the combination of favorable optical as well as electrical effects. In this work, the optical effects of two different spherical MNPs (Ag and Au nanospheres) on absorption enhancement in the active layer with the optimal thickness are analyzed in detail using finite-difference time-domain simulation. The results reveal clearly that the absorption enhancement in the OSCs is dependent on both the properties of MNPs and the types of the donor/acceptor blend systems. We conclude that Au nanospheres are less effective as compared to Ag nanospheres on absorption enhancement in OSCs, and large sized MNPs are favorable for light trapping in the organic active layer due to the prominent plasmonic excitations. For a low bandgap polymer PSBTBT:PC71BM blend system incorporating Ag nanospheres, a 11.2% increase in the integrated absorption is obtained due to the excitation of magnetic and electric resonances of surface plasmons. This work could contribute to the development of high efficiency plasmonic OSCs.

Graphene-based p-type dye-sensitized solar cells (p-DSSCs) have been proposed and fabricated using copper oxide urchin-like nanostructures (COUN) as photocathode with an FeS2 counter electrode (CE). COUN composed of Cu2O core sphere and CuO shell nanorods with overall diameters of 2 to 4  μm were grown by a simple hydrothermal method with self-assemble nucleation. It was figured out that the formation of copper oxide core/shell structures could be adjusted by an ammonia additive leading to pH change of the precursor solution. In addition to a photocathode, we also demonstrated FeS2 thin films as an efficient CE material alternative to the conventional Pt CEs in DSSCs. FeS2 nanostructures, with diameters of 50 to 80 nm, were synthesized by a similar hydrothermal approach. FeS2 nanostructures are demonstrated to be an outstanding CE material in p-DSSCs. We report graphene/COUN as photocathode and Pt/FeS2 as CE in p-DSSCs, and results show that the synergetic combination of electrodes in each side (increased interconnectivity between COUN and graphene layer, high surface area, and high catalytic activity of FeS2) increased the power conversion efficiency from 1.56% to 3.14%. The excellent performances of COUN and FeS2 thin film in working and CEs, respectively, make them unique choices among the various photocathode and CE materials studied.

Being the most widespread renewable energy generation system, photovoltaic (PV) systems face major problems, overheating and low overall conversion efficiency. The electrical efficiency of PV systems is adversely affected by significant increases in cell temperature upon exposure to solar irradiation. There have been several ways to remove excess heat and cool down the PV to maintain efficiency at fair levels. A hybrid photovoltaic/thermal system cooled by forced air circulation blown by a PV-powered fan was set up, and a rectangular control volume with cylindrical ends was built at the back of the PV panel where aluminum fins were placed in different arrangements and numbers. During the experiments, temperature and electrical output parameters were measured for three different air velocities (3.3, 3.9, and 4.5  m/s) and two different fin numbers and arrangements (54 pcs shifted and 108 pcs inline) under a constant radiation value of 1350  W/m2. While the electrical efficiency of the panel was reduced by almost 50% and decreased from 12% to 6.8% without active cooling, at 4.5-m/s air velocity and with 108 fins in inline arrangement, the electrical efficiency could be maintained at 11.5%. To compare and verify the experimental results, a heat transfer simulation model was developed with the ANSYS Fluent, and a good fit between the simulation and the test results was obtained.

The electrical characteristics of funnel-shaped silicon nanowire (SiNW) solar cells are introduced and numerically analyzed. The funnel-shaped NW consists of a cylinder over a conical unit. Its aim is to maximize the optical absorption over a large wavelength range and hence the electrical efficiency by increasing the number of resonance wavelengths or by enlarging the resonance wavelength range. The conical part has different radii in the axial direction, which increases the number of resonance wavelengths. Further, the coupling between the supported modes by the upper cylinder and the lower tapered cone offers multiple optical resonances required for broadband absorption. The optical characteristics and generation rates through the studied design are obtained using 3-D finite difference time domain. However, the electrical properties are calculated using finite element via the Lumerical device software package. In this regard, radial and axial junctions are examined for the suggested design and compared with the conventional cylindrical SiNW counterpart. In this investigation, short circuit current density, open circuit voltage, fill factor, and power conversion efficiency (PCE) are simulated to quantify the optoelectronic performance of the reported design. Furthermore, the effects of the doping concentration and carrier lifetime on the performance of the funnel-shaped design are reported. The proposed SiNWs offer PCE and short circuit density of 12.7% and 27.6  mA/cm2, respectively, for the axial junction. However, the funnel design with core–shell junction shows an efficiency and short-circuit current (Jsc) of 14.13% and 31.94  mA/cm2, respectively. Therefore, the suggested design has higher efficiency than 6.4% and 9.6% of the conventional cylindrical SiNWs according to the axial and core shell junctions, respectively.

Daylight illuminants are widely used as references for color quality testing and optical vision testing applications. Presently used daylight simulators make use of fluorescent bulbs that are not tunable and occupy more space inside the quality testing chambers. By designing a spectrally tunable LED light source with an optimal number of LEDs, cost, space, and energy can be saved. This paper describes an application of the generalized extremal optimization (GEO) algorithm for selection of the appropriate quantity and quality of LEDs that compose the light source. The multiobjective approach of this algorithm tries to get the best spectral simulation with minimum fitness error toward the target spectrum, correlated color temperature (CCT) the same as the target spectrum, high color rendering index (CRI), and luminous flux as required for testing applications. GEO is a global search algorithm based on phenomena of natural evolution and is especially designed to be used in complex optimization problems. Several simulations have been conducted to validate the performance of the algorithm. The methodology applied to model the LEDs, together with the theoretical basis for CCT and CRI calculation, is presented in this paper. A comparative result analysis of M-GEO evolutionary algorithm with the Levenberg–Marquardt conventional deterministic algorithm is also presented.