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Photonic power converters (PPCs), which convert narrow-band light to electricity, are essential components in power-by-light systems. When designed for telecommunications wavelengths such as the O-band, near 1310 nm, the devices are well-suited to power-over-fiber applications. Despite the potential for very high power conversion efficiencies ( >50% ), PPCs can be adversely affected by high-intensity nonuniform illumination conditions. In this work, we characterized two O-band PPC designs based on: high-quality InGaAsP absorber material lattice-matched to an InP substrate, and metamorphic InGaAs absorber material lattice-mismatched to a GaAs substrate, a more cost-effective and scalable alternative. We measured each device under O-band laser illumination with five beam profiles having peak-to-average ratios ranging from 2 to 11. Both devices were insensitive to the beam uniformity for input illumination with average irradiance below 2 W/cm 2 over their 5.4-mm 2 active areas, but exhibited better open-circuit voltages under larger, more uniform illumination profiles at higher incident powers. Measured efficiencies reached 52.8% and 48.7% for the lattice-matched and mismatched devices, respectively. Distributed circuit modeling results suggested that both lateral conduction losses and localized heating effects were responsible for the measured dependence on beam-size. Our work demonstrates the potential for O-band PPCs, presenting two highly efficient designs suitable for powering devices requiring ≲250 mW, with an appropriate illumination profile.

Bifacial photovoltaic technologies are estimated to supply >16% of global energy demand by 2050 to achieve net-zero greenhouse gas emissions. However, the current IEC bifacial measurement standard (IEC 60904-1-2) does not provide a pathway to account for the critical effects of spectral or broadband albedo on the rear-side irradiance, with in-lab characterization of bifacial devices limited by overestimation of rear incident irradiance, neglecting spectral albedo effects on the rear, or both. As a result, prior reports have limited applicability to the diverse landscapes of bifacial photovoltaic deployments. In this paper, we identify a general bifacial illumination method which accounts for spectral albedo while representing realistic system operating conditions, referred to as the scaled rear irradiance (SRI) method. We describe how the SRI method extends the IEC standard, facilitating indoor testing of cell or module performance under varied albedo with standard solar simulator set-ups. This enables improved comparisons of bifacial technologies, application-specific optimization, and the standardization of bifacial module power ratings., PDF file includes the supplementary information

International audience; Microstructured antireflective coatings (ARCs) can reduce reflection losses over a wide range of incidence angles when applied to the surface of a high-efficiency III-V photovoltaic cell in a concentrator photovoltaic (CPV) system. In this article, we present a microstructured ARC consisting of a monolayer of close-packed silica microbeads partially submerged within a polydimethylsiloxane (PDMS) cell encapsulant for use within a reference 500Â CPV submodule. Comparing a commercialized SiO x encapsulant to this microstructured coating with 25% submerged 1,000 nm-diameter beads, angle-dependent external quantum efficiency measurements yield a 2.6% current gain for the microstructured coating. Simulations demonstrate good agreement with measurements, predicting a 2.4% current gain for the same configuration. Extrapolating with our validated model, we estimate a maximum and achievable (within a large manufacturing tolerance) current gain of 3.4% and 2.9 ± 0.4% using 60% submerged and 10%-32% submerged 760 nm-diameter beads, respectively.

We designed and optimized ultra-thin single junction InAlGaAs photonic power converters (PPC) with integrated back reflectors (BR) for operation at the telecommunications wavelength of 1310 nm and numerically studied the light trapping capability of three BR types: planar, cubic nano-textured, and pyramidal nano-textured. The PPC and BR geometries were optimized to absorb a fixed percentage of the incident light at the target wavelength by coupling finite difference time-domain (FDTD) calculations with a particle swarm optimization. With 90% absorptance, opto-electrical simulations revealed that ultra-thin PPCs with 5.6- to 8.4-fold thinner absorber layers can have open circuit voltages (Voc) that are 9-12% larger and power conversion efficiencies (PCE) that are 9-10% (relative) larger than conventional thick PPCs. Compared to a thick PPC with 98% absorptance, these ultra-thin designs reduce the absorber layer thickness by 9.5-14.2 times while improving the Voc by 12-14% and resulting in a relative PCE enhancement of 3-4%. Of the studied BR designs, pyramidal BRs exhibit the highest performance for ultra-thin designs, reaching an efficiency of 43.2% with 90% absorptance, demonstrating the superior light trapping capability relative to planar and cubic nano-textured BRs.

Subcell segmentation is a method to obtain nearly ideal current-matching while employing nonideal bandgap combinations in high-efficiency multijunction solar cells. By splitting each subcell into multiple semitransparent pn junctions, called segments, current-matching can be satisfied by layer design rather than material selection. This architecture replaces the standard requirement for an optimal combination of bandgaps with a simpler requirement for optimal layer thicknesses in each series-connected segment. The total device current is divided across all segments, reducing the resistive power loss especially under nonuniform illumination or high to extreme concentration. Detailed balance-based analysis of three- and four-subcell devices in both terrestrial concentrator and one-sun space applications demonstrates that the segmented architecture can approach the theoretical efficiency peak using a broad range of physically realizable bandgap combinations. For example, detailed-balance analysis reveals a 7.5%–8.1% absolute efficiency improvement for 1-cm2 segmented cells compared with standard InGaP/InGaAs/Ge designs under 1000-suns AM1.5D illumination. Higher-order segmentation multiplies the number of segments in all subcells by a common multiple, which further reduces the device current, resistive power loss, and segment thicknesses.

Among the racking elements of bifacial photovoltaic (PV) single-axis tracked systems, the torque tube (TT) introduces the most shading and reflection, increasing irradiance nonuniformity and electrical mismatch loss. We simulate the impact of TT shading and reflection on the irradiance profiles, electrical mismatch, and energy yield for central bifacial PV modules on one-in-portrait (1P) and two-in-portrait (2P) single-axis trackers. TT reflection increases annual irradiance in 1P and 2P systems by 0.17% and 0.30%, respectively. Overall, TT reflection increases the predicted instantaneous energy yield by up to 0.8% and 0.4%, and the annual energy yield by 0.11% and 0.18% in 1P and 2P systems, respectively.

Enormous potential lies in waste-heat recycling for the world’s industrial sector. Portable solid-state modules are a universal low-maintenance method to recycle this waste-heat. One such technology, near-field thermophotovoltaics (NFTPV), relies on a heat source in extreme proximity (

We discuss the integration of quantum dashes (QDashes) into laser simulations using Crosslight Pics3D, outlining the approach for developing a model featuring asymmetrical active regions. The importance of including wetting layers to accurately represent carrier transport is investigated using results obtained for an InAs/InP QDash laser. While leakage current across the active region is unaffected by the absence of wetting layers, their presence enhances Auger recombination losses in the active region, leading to lower overall device efficiencies.

Waste heat is a free and abundant energy source, with 15% of global total energy use existing as waste heat above 600 K. For 600–900 K temperature range, near-field thermophotovoltaics (NFTPVs) are theorized to be the most effective technology to recycle waste heat into electrical power. However, to date, experimental efficiencies have not exceeded 1.5%. In this work, we optimize the efficiency of three modeled InAs/InAsSbP-based room-temperature NFTPV devices positioned 0.1 μm from a 750 K p-doped Si radiator. We couple a one-dimensional fluctuational electrodynamics model for the near field optics to a two-dimensional drift-diffusion model, which we validated by reproducing measured dark current–voltage curves of two previously published InAs and InAsSbP devices. The optimized devices show four to six times higher above-bandgap energy transfer compared to the blackbody radiative limit, yielding enhanced power density, while simultaneously lowering parasitic sub-bandgap energy transfer by factors of 0.68–0.85. Substituting InAs front- and back-surface field layers with InAsSbP show 1.5- and 1.4-times higher efficiency and power output, respectively, from lowered parasitic diffusion currents. Of our three optimized designs, the best performing device has a double heterostructure with an n–i–p doping order from front to back. For radiator-thermophotovoltaic gaps of 0.01–10 μm and radiators within 600–900 K, this device has a maximum efficiency of 14.2% and a maximum power output of 1.55 W/cm2, both at 900 K. Within 600–900 K, the efficiency is always higher with near- vs far-field illumination; we calculate up to 3.7- and 107-times higher efficiency and power output, respectively, using near-field heat transfer.

The effect of encapsulant on solar cell performance is widely understood to decrease overall cell power output due to absorption in encapsulating layers. In this work, we quantify the effect of encapsulation across the solar spectrum for high-efficiency bifacial silicon heterojunction solar cells in Synopsys TCAD Sentaurus to determine whether encapsulation causes a significant deviation in current loss trends compared to bare cells. Bare and encapsulated cells are modelled between 300-1200 nm and for air masses (AMs) between 1 and 10.0. Comparing current densities relative to bare cells for front illumination, encapsulation results in a 4.3% increase in parasitic absorption under AM1 illumination, and a 3.9% increase at AM10 as a consequence of the red-shift under higher AM. Despite spectral effects influencing current loss, trends of efficiency with AM are the same for bare and encapsulated cells, peaking around AM5. Encapsulated efficiency is decreased by 1.40 ± 0.02 % abs. compared to bare cells between AM1-10. Thus, while carrier transport is influenced by encapsulation in a wavelength-dependent manner, the overall effect on cell efficiency is a uniform offset for all spectra considered.

As quantum dash laser designs gain technological maturity, there is a need to investigate performance limiting factors. We simulate monolithic ridge waveguide quantum dash (QDash) and quantum well (QW) lasers in the InGaAsP/InP-system to investigate the mechanisms limiting device performance at elevated temperatures. Our findings are compared to experimental data obtained for representative devices. We quantify dominant loss mechanisms as a function of injection current density at different temperatures and compare results for QW and QDash structures. We find a variation in relative loss contribution between devices. At higher temperatures we find Auger recombination emerging as the dominant loss mechanism., 2021 Photonics North (PN), May 31 - June 2, 2021, Toronto, ON, Canada

International audience; Micro-concentrator photovoltaic (CPV), incorporating micro-scale solar cells within concentrator photovoltaic modules, promises an inexpensive and highly efficient technology that can mitigate the drawbacks that impede standard CPV, such as resistive power losses. In this paper, we fabricate micro-scale multijunction solar cells designed for micro-CPV applications. A generic process flow, including plasma etching steps, was developed for the fabrication of complete InGaP/InGaAs/Ge microcells with rectangular, circular, and hexagonal active areas down to 0.089 mm 2 (0.068-mm 2 mesa). Large cells (>1 mm 2) demonstrate good electrical performance under one sun AM1.5D illumination, but a degradation in the open-circuit voltage (V OC) is observed on the smallest cells. This effect is attributed to perimeter recombination for which a passivation effect by the antireflective coating partially recovers the V OC. The V OC penalty for small cells is also reduced under high-intensity illumination, from 3.8% under sun to 1.0% at 974 suns. High intensity illumination yields an efficiency of 33.8% under 584 suns for a 0.25-mm 2 and microcells are expected to show higher efficiency than standard cells under very high concentration.

The use of III-V and group IV compounds in the same heterostructure is of great interest for high performances solar cells under concentration. In fact, the combination of these III-V and group IV compounds can lead to interesting strategic bandgap choices and engineering to better match the absorption of the solar spectrum, and therefore better solar cell performance. The series-connected quad-junctions (4J) solar cell strategies have the potential to improve solar cells performance and therefore enable low-cost concentrator photovoltaic (CPV) systems, allowing lower levelized cost of electricity (LCOE) from a CPV system. This work presents the investigation of the performance of dual junction (2J) GaInP/GaAs that might be implemented as upper cells with group IV (SiGeSn) cells as bottom cells. The aim of this study is to validate the epitaxial structure and the fabrication process for future 4J cells development. Pitch is varied from 125 μm to 400 μm for two different size of cells, in order to optimize solar cells performance under concentration (X) In the range of 100X to 1000X. Solar cells demonstrated high fill factor (FF) values and ideality factors (n) approaching unity per subcell have been obtained in the range of 100X to 500X. A FF of 85% and 88% are obtained at a concentration of 1000X for the bigger and smaller cells respectively, for the narrowest pitch. These results close to the state-of-the-art are encouraging for the implementation of this 2J with IV bottom subcell for the purpose of high performance 4J.

Bifacial photovoltaics present a clean and cheaper alternative to diesel generators for high-latitude remote communities; however, solar cells are tested at air mass 1.5, while average air mass increases with increasing latitude. For example, Cambridge Bay (69oN) has an irradiance-weighted average air mass of 3.1. We demonstrate improved efficiency of bifacial silicon heterojunction modules under high air mass spectra due to reduced incident UV light. We implement air mass correction in our bifacial PV modelling software, and we quantify the impact of air mass on energy yield for fixed-tilt and tracked systems in high latitude locations.

Photonic power converters (PPCs) are one of the main components of optical power transmission systems, generating electrical power via the photovoltaic effect. We simulate ultrathin PPCs designed for operating at the telecommunication wavelength of 1310 nm with 9 and 12 times thinner absorbing layers using cubic and pyramidal nanostructured back reflectors (BRs), respectively. While increasing efficiency by 13% (rel.) over conventional PPCs, results also show superior light trapping for pyramidal BR with twice the absorption of a simple double pass absorber layer of the same thickness and higher short-circuit current for pillar BR reaching 94% of an ideal Lambertian surface.

The absorption of rear-side irradiance in bifacial solar cells affects carrier generation rates, recombination rates, and series resistance, increasing the complexity of quantifying bifacial cell performance. In this work, recombination rates and the electronic structure of textured bifacial silicon heterojunction solar cells are modelled in Synopsys TCAD Sentaurus. Front and rear illumination conditions vary in air mass from 1.5 to 10.0, while the effect of shifting spectrum and intensity due to snow and dry-grass albedo are applied to rear-side light. Recombination rates in the depletion region remain constant for different illumination scenarios, while throughout the bulk they are ∼1 order of magnitude larger for rear illumination compared to front illumination, resulting in a simulated bifaciality within 0.1% of experiment (97.4%). With increasing air mass, the average c-Si recombination probability varies by

We present a two-junction photonic power converter operating under monochromatic illumination in the telecommunications O-band. The design, which is a direct extension of multi-junction solar cell technology, incorporates InAlGaAs absorbing layers lattice-matched to InP. Multi-junction detailed balance calculations are presented to benchmark device performance. A transparent tunnel diode with peak tunneling current near 1000 A/cm2 provides a series connection between the subcells. Current-voltage measurements under laser illumination at 1319 nm yield ideality factors near 1, with open-circuit voltages up to 0.38 V and 0.66 V for the one- and two-junction devices, respectively, under intensities of up to 0.33 W/cm2. Quantum efficiency measurements reveal that the two-junction device is current-matched near 1390 nm.

Silicon phthalocyanines have been identified as a potential non-fullerene electron acceptor in organic photovoltaics. Bis(tri-n-butylsilyl oxide) silicon phthalocyanine ((3BS)2-SiPc) is shown to be a direct replacement for phenyl-C61-butyric acid methyl ester (PC61BM) with poly(3-hexylthiophene) (P3HT) in bulk heterojunction organic photovoltaics. Devices fabricated with a P3HT:(3BS)2-SiPc active layer displayed a power conversion efficiency (PCE) of 3.6% alongside a Voc of 0.76 V. These novel devices exhibited higher PCEs over a wide range of incident angles and light intensities, while also operating at longer wavelengths compared to devices with a P3HT:PC61BM active layer. This merits future investigation into commercial applications.

At high latitudes, bifacial photovoltaics are expected to achieve significant bifacial gain due to the albedo of snow, but irradiance will include a wide range of incident angles and high air mass spectra. We studied the performance of bifacial silicon heterojunction solar modules with increasing angle of incidence and air mass to derive an incidence angle modifier and air mass modifier for short circuit current. We found that the incidence angle modifier remained constant with varied air mass, allowing the incidence angle modifier and air mass modifier to be applied independently. Module correction factors were applied to the SUNLAB's energy yield model, DUET. We demonstrate that the impact of air mass on energy yield increases with latitude and can reach >2.5% on an annual basis for single-axis tracked modules and >2% for fixed latitude-tilt modules in high-latitude locations. This is highly dependent on season, with greater impact in off-summer months, reaching >6.5% monthly air mass impact for a high-latitude location in winter. These results demonstrate that air mass effects are more significant for high-latitude locations, and should be considered in energy yield calculations.

The external quantum efficiencies of three bifacial silicon solar cell structures were measured at various incident light angles. The resulting short circuit current densities and bifacialities of an a-Si/c-Si heterojunction cell were compared over front and rear faces to determine their relative performance and incidence angle modifier for energy yield calculations. The heterojunction cell had the highest bifaciality of the cells considered.

Bifacial photovoltaics present a clean and cheaper alternative to diesel generators for high-latitude remote communities; however, solar cells are typically tested at 0° angle of incidence, 25°C, and AM1.5, from which high-latitude conditions vary greatly. A bifacial silicon photovoltaic cell optimized for high-latitude conditions will improve energy yield for these systems. We integrate experimentally-derived cell parameters with a systems-level model capable of fixed-tilt and tracked energy yield predictions. We optimize to find the most efficient cell design for high-latitude environments in Sentaurus and SunSolve and determine the resulting improvement in energy yield for an entire panel in MATLAB.

International audience; Concentrator photovoltaic (CPV) systems that use silicone-on-glass Fresnel lenses as their primary optical element have reduced power output at high and low lens temperatures. We show that incorporating a nanostructured surface on the solar cell stabilizes best module performance over an extended operating temperature range. We model the optical properties of a self-organized monolayer of glass beads deposited on a polydimethylsiloxane (PDMS) encapsulated solar cell in a CPV sub-module. Our model combines transfer matrix method (TMM), rigorous coupled wave analysis (RCWA), and ray tracing to quickly and accurately simulate the system. We find the short-circuit current gain increases as the lens deviates from its designed working temperature for all bead sizes, and that 400 nm diameter beads submerged halfway into PMDS have the highest gain (up to 2.6%).

Detailed balance calculation of subcell segmentation in the extension of the InGaP/InGaAs/Ge system to 4-subcell designs shows performance above the level of the standard optimal bandgap is achievable in conjunction with other practical advantages.

We investigate the effect of incident spectra on current loss as a function of depth and voltage into high efficiency textured bifacial silicon heterojunction solar cells. We integrate thin-film ellipsometry measurements with a 3D optical model and a 2D electronic model and validate our model with measurements of external quantum efficiency and Suns-Voc. For front illumination at normal incidence, an increasing air mass of AM1.5 to 10 reduces current density loss due to parasitic absorption in ITO and a-Si:H from 8.1% to 4.0%, and increases recombination loss at maximum power from 4.2% to 4.7%, resulting in an overall increase in collected current (88.2% to 90.5%). Cell performance metrics are summarized as a function of air mass, with efficiency peaking at AM5.0 for front illuminated and rear illuminated cells with an albedo of unity. We further demonstrate the impact of spectra on bifacial efficiency by calculating rear-side performance with the spectral albedo of dry grass. Overall, current-collection and efficiency trends emphasize the importance of considering spectral effects in energy yield models. These results are of particular importance for cell structures with high bifaciality and significant spectral albedo contributions, locations with large proportions of diffuse light, and high air mass locations as in mid-to-high latitudes.

We present modeled detailed balance efficiency of multijunction photonic power converters operating at 1310 nm at a laser intensity of 5.88× 105 W/m2, corresponding to our test laser power and cell size, in two scenarios: (1) with an absorbing substrate and (2) with a perfect specular back reflector. We show that, in the radiative limit, efficiency increases as a function of number of junctions in the case of an absorbing substrate. In this case, efficiency can reach as high as 69% with 15 junctions. In the case of a perfect specular back reflector, efficiency reaches more than 75% and is not sensitive to the number of junctions. This insensitivity allows freedom in future device design.

Two-dimensional optoelectronic modelling of bifacial silicon heterojunction solar cells is completed in Synopsys TCAD Sentaurus to optimize and characterize cell performance for regions of high latitude where cells experience high average air mass and increased angles of incidence. Cell performance under bifacial illumination conditions representative of the Canadian High Arctic, with independent spectra illuminating the front and rear faces of the cell, is studied. The baseline cell structure has an efficiency of 20.4% and 19.3% under front-face illumination with AM1.5G and AM3.0G, respectively. Improvements will be made through the addition of surface texturing and the optimization of doping, layer thicknesses, and antireflection coatings.

This paper presents a bifacial PV energy yield simulation tool with highly-parameterized optical and electrical models. The resulting detailed irradiance profiles provide insight into the effects of rack shading. Horizontal parallel wiring architecture of cells in the module is found to mitigate nonuniform rear irradiance caused by torque tube shading in a single-axis tracked system for representative cloudy and clear days. Low cell shunt resistance is shown to amplify bifacial gain during low irradiance hours. Annual energy yield predictions for fixed and tracked bifacial PV systems for Ottawa, ON are also presented.

We show the high efficiency and voltage possible for a monochromatic multijunction photovoltaic device operating at the telecommunication wavelength 1310 nm. We use InAlGaAs lattice matched to InP and characterize our single-junction test structure, which we show has a bandgap of 0.864 eV. We use an extended detailed balance model to predict the efficiency and voltage of a series-connected multijunction device built from the same material, and show its advantages compared to a single-junction design. We show that a series-connected 20-junction device with In 0.532 Al 0.097 Ga 0.371 As can achieve a maximum power conversion efficiency over 69% in the radiative limit, at an input intensity of 5.6 × 105 W/m2. We also show that the device voltage at the maximum power point increases linearly with the number of junctions, with a slope larger than the single-junction voltage at maximum power point. Such behaviors of voltage and efficiency make a promising future for high-efficiency, high-voltage multijunction photonic power converters near 1310 nm.

Bifacial photovoltaics at high latitudes can achieve up to 25-45% bifacial gain due to high-albedo snow cover and high proportion of diffuse light. We studied the angular performance of bifacial silicon heterojunction solar cells with various textures to understand high-latitude effects on optical losses. For cone and pyramid-patterned designs, external quantum efficiency decreases at high angles, primarily due to increased reflectivity, although longer path length through front-surface films also increases UV losses for all surface types. At 80° incidence and 25°C, a

Multi-junction solar cell design can be enhanced using a process of subcell segmentation, whereby each subcell is further sub-divided into multiple optically-thin pn junctions. This design increases output voltage, reduces current (and associated resistive losses), and crucially, adds a degree of freedom to achieve current-matching across segments (controlled by epitaxial layer thicknesses) rather than across subcells (controlled by material bandgap). This design expands the highest efficiency region of the bandgap design space, pivoting away from the need to obtain ideal bandgap combinations for the highest efficiencies.

Development of a photonic power converter for operation at 1310 nm would enable long distance optical power transfer over fiber. InAlGaAs lattice-matched to InP may be used as the absorber material in such a device. Material properties of InAlGaAs grown by molecular beam epitaxy (MBE) are studied by techniques including electro- and photoluminescence, spectroscopic ellipsometry, and quantum efficiency.