Multi-junction all-perovskite tandem solar cells (A-PTSCs) can achieve higher power conversion efficiency (PCE) value beyond the Shockley-Queisser limit of single-junction perovskite solar cells (PSCs). However, only one side of the substrate is used in traditional two-junction tandem devices architecture, so that two-terminal (2-T) tandem devices require the preparation of a high quality and complex interconnection layer (ICL) to connect the two sub-cells and four-terminal (4-T) tandem devices require two substrates for two sub-cells. Here we demonstrate a two-junction A-PTSC using a double-sided ITO (D-ITO) glass substrate. The wide bandgap (W-Eg) perovskite (1.75 eV) as the upper cell and the narrow bandgap (N-Eg) perovskite (1.21 eV) as the bottom cell are deposited on both side of the D-ITO substrate, respectively. By changing the wiring method, on a substrate, 2-T, three-terminal (3-T), and 4-T integrated A-PTSC are obtained with efficiencies of 21.17% for 2-T tandem architecture, 17.71% for 3-T and 21.55% for 4-T. The concept and design here represent a new architecture toward A-PTSCs.

This paper describes the fabrication of bandgap grading Sb2(S,Se)3 solar cells via sputtering and post-selenization/sulfurization using SeS2 powder as a sulfur source. The material characteristics and photovoltaic performances of the solar cells were assessed as functions of S/(S + Se) ratio. In experiments, an appropriate S/(S + Se) ratio resulted in grains with the preferred vertical orientation and fewer grain boundaries (GB) to hinder carrier transport, which together reduced charge transfer resistance. A suitable S/(S + Se) ratio also resulted in an S depth profile with a V-shaped distribution, which allowed bandgap grading in the depletion region. An excessively high S/(S + Se) ratio gradually altered the energy band at GBs from downward bending to upward bending, which increased the likelihood of electron-hole recombination at GBs. A high S/(S + Se) ratio also promoted excessive grain growth in various directions, which increased surface roughness and prevented the uniform coverage of the CdS layer, thereby reducing device performance. The optimal S/(S + Se) ratio of 0.27 resulted in a power conversion efficiency (PCE) of 7.1%, which is a new efficiency record for antimony chalcogenide-based thin film solar cells prepared via sputtering and post-selenization.

Concentration photovoltaics are used to achieve solar energy focusing on small-area solar cells, thus obtaining a high efficiency at a reasonable cost. An array of gold plasmonic concentrator cells is proposed here, which can nano-focus the solar radiation down to 60 nm spot size. It works over the entire solar energy bandwidth up to 2400 nm wavelength, which is extended beyond the conventional solar cells known maximum operating wavelength of 1800 nm. The concentrator consists of a coaxial waveguide with a tapered section that can plasmonically nano-focus solar radiation, followed by a straight waveguide section to propagate focused light along a graphene metamaterial for optical absorption. The metamaterial is integrated within the 60 nm gap of the straight waveguide section. The metamaterial consists of 10 concentric graphene shell layers, which are cross-connected by 5 horizontal graphene annuli. The concentrator and metamaterial design maximizes the solar optical absorption efficiency within the graphene metamaterial. The graphene optical absorption is enhanced up to 27 times with an almost flat response covering most of the solar bandwidth. The plasmonic absorption within the gold surfaces of the structure is found to be reasonable. The enhanced optical absorption of the weak solar radiation received within the extended band (1800–2400 nm) can reach up to 50%. The concentrator device is polarization insensitive with a 120o field-of-view. The enhanced optical power absorption in graphene metamaterial could be used in photovoltaic energy harvesting applications.

Reducing the width of conductive silver wires, increasing the aspect ratio, improving the utilization rate of silver paste, and enhancing the uniformity of silver wires are key issues that need to be addressed in the manufacture of solar cells. This article explores the feasibility of using glass nozzles to directly write ultra-high viscosity silver paste containing micrometer-sized particles. By preparing a glass nozzle with a diameter of 45μm, conductive silver wires with an average width of about 43±2μm and an aspect ratio of up to 0.96 can be printed. After high-temperature sintering, the width of the silver wire is 32±2μm, the aspect ratio is 0.95, and the resistance of the finger line is 0.13 Ω/cm. In addition, the conductive silver paste is a Herschel–Bulkley (HB) non-Newtonian fluid. Combining the constitutive equation of the HB fluid, a mathematical model of the silver paste flow inside the nozzle is established. Therefore, the influence of characteristic parameters of the silver paste/nozzle on the printing process can be intuitively understood.

Converting the UV-blue irradiation into longer wavelength can efficiently ameliorate the insufficient solar spectral response and enhance the power conversion efficiency (PCE) of silicon solar cells, whereas there is still no appropriate strategy to make the corresponding luminescence downshifting materials compatible with commercial silicon photovoltaic modules practically. Herein, we first demonstrate an in-situ fabricated CsPbBr3 PQDs/POE encapsulation adhesive film, which can simultaneously achieve continuously large-scale manufacture through melt extrusion and possess well compatibility with the encapsulation technique of silicon photovoltaic modules. According to the separate granulation preparation and technical optimization, the composited adhesive film exhibits an intensive PL emission at 515 nm with a full width at a half-maximum of 20 nm and an ultra high PLQY of 98.2%. Moreover, less than 5% PL intensity decline even after keeping in 50 °C/90 RH aging condition for >2400 h proves its excellent working stability and barrier property. By means of hot pressing operation, the silicon solar cells encapsulated with CsPbBr3 PQDs/POE adhesive film harvest an absolute PCE enhancement of 0.68%. This work provides a way of great potential towards further improving the silicon photovoltaic industry and corresponding optoelectronic applications.

Reports showing that hydrogen and group-III acceptors play an important role in Light- and elevated Temperature-induced Degradation (LeTID) of Si-based solar cells highlight the need for a better understanding of interactions between these two species. In this contribution, a combination of junction spectroscopy techniques and first principles modelling has been used to study hydrogen-induced changes in electrical properties of either boron or gallium Czochralski-grown silicon co-doped with phosphorus in order to produce n-type material facilitating novel techniques to assess recombination active defects. The interactions of hydrogen with acceptor atoms have been induced via annealing of these co-doped hydrogenated samples with the application of reverse bias (RBA). These treatments have resulted in a significant increase in the net shallow donor concentration in depletion regions of both materials and in the appearance of a strong electron emission signal due to a trap with an energy level at about Ec −0.18 eV in the DLTS spectra of Si:P + B material. It is argued that this trap is related to the donor level of a BH2 complex. Calculations using density functional theory have shown that the BH2 defect has a charge-state dependent geometry, which turns out to be crucial for the proposed non-radiative recombination mechanism. The BH2 defect is therefore suggested to be the root cause of LeTID in boron-doped Si. In contrast, modelling results predict that GaH2 is a defect with shallow energy levels, without the characteristic features of a recombination centre. This is corroborated by the results of electrical measurements on hydrogenated Si:P + Ga subjected to RBA. Conventional annealing treatments were subsequently used to assess the thermal stability of acceptor-H related defects. Based on the obtained results, the peculiarities of hydrogen interactions with boron and gallium acceptors are discussed.

The vehicle integrated photovoltaic (VIPV) technology, which consists in integrating PV solar panels in the surfaces of electric vehicles, is a promising technology to increase car autonomy. Free-form curved PV surfaces are demanded to meet the specific design constraints of the automotive. The proper characterization of three dimensional PV surfaces requires specific methods and equipment that must be developed. This paper describes the design principles and requirements of a solar simulator for characterization of curved PV modules. Its effectiveness is demonstrated by means of ray-tracing simulations, the results show the advantages provided by the use of a collimated light source in comparison to the conventional solar simulators used for flat modules. The light beam divergence of a non-collimated light source produces a non-uniformity boost between 2% and 20% depending on the module size and curvature. The module performance will be affected by this non-uniform irradiance, but the performance loss will also depend on specific characteristics of the module such as curvature, number and size of cells, series/parallel electrical connection and number of by-pass diodes. On the contrary, the proposed collimated solar simulator reproduces the solar illumination profile over the curved surface. The Helios 3198, a solar simulator with collimated light developed for concentrator modules, has been adapted accordingly to the design proposed. A module of 1 m of curvature has been tested, the short-circuit current of the cells follows the ideal cosine response of the curvature, differences are lower than 0.5% which proves the quality of the collimated beam.

We have investigated bifacial Ge-incorporated Sb2Se3 thin-film solar cells by modeling and simulating a back buffer layer including Cu2O to optimize the bifacial device performance. A Ge-incorporated Sb2Se3 absorber layer was grown using Vapor Transport Deposition to extract the input parameters for the simulation, followed by exploring the properties of the transparent back buffer layer. After selecting a Cu2O back buffer layer, we conducted the optimization study of bifacial Ge-doped Sb2Se3 devices by varying a set of devices and materials parameters. The optical bandgap is characterized as 1.23 eV for Ge-incorporated Sb2Se3 absorber and the absorption coefficient is 3 × 105 cm−1 at 600 nm. Using these input parameters, we simulated the device configuration of ZnO:Al/i-ZnO/CdS/Ge-Sb2Se3/back buffer layer/transparent conductive oxide. Firstly, we checked the impact of conduction and valence band offsets on device performance, indicating the valence band offset of the back buffer layer plays a significant role. In particular, zero or small positive valence band offset minimizes a Schottky hole barrier, which could reduce hole current clamping near the back buffer region. As for back buffer doping concentration, high back buffer doping concentration (1 × 1015 cm−3 or higher) is required to improve device performance even with zero valence band offset, whereas low absorber doping concentration (<1 × 1014 cm−3) enables higher efficiency due to the enlarged energy band bending. For bifacial device performance, a Cu2O back buffer layer is simulated by varying critical input parameters such as absorber thickness, doping concentration, and defect concentration near the back buffer interface. The best efficiency of front-side illumination is 19.7%, Voc (744.4 mV), Jsc (40.14 mA/cm2), and FF (66.1%) and that of the rear-side illumination is 13.0%, Voc (724.5 mV), Jsc (31.6 mA/cm2), and FF (56.7%). Consequently, the bifaciality factor is 66%.

Thermophotovoltaic (TPV) cells convert thermally emitted photons into electrical power using photovoltaic (PV) detectors. To realize highly efficient thermal energy harvesting using TPV conversion, high-temperature stable spectrally-selective emitters are needed. The deployment of TPV technology lags behind conventional solar-PV technology due to the lack of large-scale fabrication of efficient thermal emitters, which would preferentially emit in the PV cell absorption band. In this work, we demonstrate a simple large-area nanofabrication method based on the hole-mask colloidal lithography and sputtering, which allows one to fabricate tungsten (W) nanodisc spectrally-selective emitters (consisting of a metal-insulator-metal configuration) with a high emissivity below the InGaAsSb PV-cell cut-off wavelength of 2.25 μm and a gradually decreasing emissivity (down to < 10%) in the mid-infrared region. Frequency-domain time-domain (FDTD) simulations reveal that the spectral selectivity is achieved due to the localized surface plasmon resonance of W nanodiscs strongly influenced by the insulator thickness. Importantly, the W emitters show thermal stability at temperatures of up to 1100 °C, and emissivity invariance to changes in polarization and incidence angles up to 65°. This work represents a significant step towards the realization of high-temperature stable efficient thermal emitters by a facile and cost-effective fabrication method, thereby promoting the implementation of photonic/plasmonic thermal emitters in the next-generation thermal energy harvesting systems. The method proposed in this study holds potential for scalability; however, empirical evidence to demonstrate this scalability has not yet been established. Subsequent studies are needed to confirm the scalability of the proposed method and its extensive applicability.

This work demonstrates the reduction of cutting-induced losses on tunnel-oxide passivated contact (TOPCon) shingle solar cells via edge passivation using high-throughput layer deposition. TOPCon shingle solar cells with a size of 26.46 mm × 158.75 mm are separated from industrial full-square TOPCon host cells either by laser scribing and mechanical cleaving (LSMC) from the emitter-free rear side or by thermal laser separation (TLS) from the front side. TLS yields up to 0.2%abs more efficient shingle cells directly after singulation in comparison to shingle cells that have been separated by LSMC. Passivated edge technology (PET) is applied by depositing aluminum oxide (Al2O3) layers using two different tools: thermal atomic layer deposition (T-ALD) in a lab-scale tool with a throughput of tens of shingle cells per hour and a high-throughput plasma-enhanced ALD (PE-ALD) prototype tool with a throughput of about 60,000 shingle cells per hour. The energy conversion efficiency of the edge-passivated shingle cells after T-ALD Al2O3 PET is found to be 0.4%abs higher than directly after separation. This gain is the same regardless of whether LSMC or TLS is used for cell separation. For PE-ALD Al2O3 and TLS, a gain of 0.5%abs is measured after PET. Stringing tests with electrically conductive adhesive so far indicate that Al2O3 layers do not negatively affect the resistance of cell to cell interconnections. Thus, low-damage cell cutting in combination with high-throughput Al2O3 layer deposition for edge passivation is a very promising approach to maintain high efficiency for industrial TOPCon solar cells in shingled modules.

Benzyl viologens (BVs) have garnered massive attention due to their remarkable functional ability as a cathodically coloring material and glare reduction agent in electrochromic devices (ECDs). However, BV-based ECDs have some challenges, of which dimer formation due to viologen radicals is foremost, as it extensively damages the device performance. Herein, a new approach is proposed to address this issue in which five novel fluorine-substituted benzyl viologen (FSBV) are synthesized through a multi-step route based on the fluorine-atom count on the viologen moiety. Once synthesized, the FSBVs (0.01 M) were employed as an electrochromic material (ECM) along with tetrabutylammonium tetrafluoroborate/propylene carbonate (0.5 M TBABF4/PC) as a supporting electrolyte and ferrocene (0.05 M Fc) as a counter electrode material in an ECD assembly. We observed that the family of FSBV-based ECDs demonstrated suppressed dimerization tendency, higher optical contrast, fast response time, and enhanced cycling stability compared to the pristine benzyl viologen-based device (BV/Fc ECD). In particular, PFBV/Fc ECD (from the FSBV family), that utilizes 1,1ʹ-bis(2,3,4,5,6-pentafluorobenzyl)-4,4ʹ-bipyridine 1,1ʹ-diium tetrafluoroborate (PFBV) as an ECM, exhibited higher optical contrast (ΔT) of ∼63.6%, high coloration efficiency of ∼304 cm2/C, fast switching time of ∼1.2 s and an excellent ΔT retention of ∼97% after 10,000 cycles, all at 603 nm. The exciting feature of this study lies in the deployment of a highly sensitive and non-invasive technique, electrochemical quartz crystal microbalance (EQCM), to monitor the ultrasmall mass transmutations caused by synthesized chromophores at the electrode/electrolyte interface. The EQCM analysis revealed that the molecular structure of maneuvered viologen derivatives has a decisive role in determining the mass exchange behavior at the quartz crystal surface, which is reflected in a dissimilar degree of electrochromic performance.

Solid-solid phase change materials (SSPCMs) with low volume change, no leakage, lack of corrosion and extensive service lives are used more and more widely in the application field of thermal energy storage (TES). In this study, eco-friendly polylactic acid (PLA)/polyurethane (PU) phase change composites with good recyclability and excellent form stability for TES were obtained by melt blending in a twin-screw eccentric rotor extruder. The experimental results show that the introduction of PLA is helpful to enhance the mechanical strength and leak-free performance of the PLA/PU composites. When the content of PLA achieved 20% in the PLA/PU composites, the relative enthalpy efficiency (η) of PP-20 is 79.14%, which is beneficial for the function of TES. Especially, PP-40 showed excellent flexibility, reversibility and durability whose tensile stress (14.0 MPa) and tensile strain (48.15%) were pretty good at room temperature. After reprocessed many times, PP-40 showed good recyclability whose enthalpy of fusion reduced (60.69 J/g) but could still reach 91.51% of the original. The above results imply that the PLA/PU composites provide an efficient way for the green use and reprocessing of SSPCMs in the field of TES.

Here we synthesize a waterproof cross-linked gasochromic thin film obtained by incorporating Prussian blue nanoparticles, polyvinyl alcohol, crosslink agent: 3-glycidoxypropyltrimethoxysilane and catalytic platinum nanoparticles, applied by a single coating and heat process onto a substrate. The cross-linked polyvinyl alcohol-Prussian blue (PVA-PB) films reveal an excellent hydrophilic character. The contrast ratio at 700 nm reaches 87.2. The cycle stability exceeds 200 cycles. The switching time from deep blue to transparency took 14.3 s for bleaching and 600 s for darkening. Surface electron microscopy, electrochemical analysis and Fourier-transform IR spectroscopy were used to investigate a series of waterproof Prussian blue films. The results showed the redox mechanism between polymer matrix, chrome and catalytic nanoparticles.

Concentrated Solar Power (CSP) receivers, especially those adopted in Solar Tower (ST) configurations, operate at high temperatures and low stresses making them susceptible to creep damage. Creep modelling used to predict components' life and therefore the accuracy of creep modelling can significantly impact life estimation, prediction of failures, and ultimately the design. The accuracy of creep modelling is highly variable and depends on the choice of model, the choice of fitting functions, and sometimes depends on ‘judgement’ decisions by the modeller. In this article the Larson-Miller and Wilshire creep models are fitted to three common power generation materials (Grade 22, SS316 and Inconel 740H) with differently sized datasets. Region splitting via activation energy is also examined. The fits are examined for accuracy and bias for stress, temperature and rupture time by a statistical process of bootstrapping to provide a better understanding of the impact of the creep model and dataset size on the design and lifing of CSP receivers.

Renewable energy from a natural resource is currently significant awareness and is being discussed by researchers worldwide to solve the energy crises. This work paves the way for developing efficient solar-to-thermal energy storage conversion based on the “Soft-rigid” structural formation mechanism of carbon aerogel. Here, low-cost wasted pomelo peels derived three-dimensional (3D) porous networked carbon aerogels (PCAs) as a support matrix for paraffin wax (PW) as organic phase change materials (PCM). Moreover, composite phase change materials (CPCMs) show ultralow density, excellent thermal stability, enhanced thermal and electrical conductivities, outstanding shape stability, and leakage-proof ability. The impregnation loading ratio of PW-based CPCM3 reached 95.6%, ascribed to the unique “Soft-rigid” network structure of PCAs. More importantly, the change in the “Soft-rigid” structure endows PCA750 with a high compressive strength of 466 kPa at 60% compression rates. The obtained CPCM2 displayed a significant latent thermal storage capacity of 159.9 J/g and exhibited superior thermal reliability after 25 frequent heating/cooling cycles. The effective carbonization temperature of CPCM2 caused a significant increase in light absorbance; thus, high solar-to-thermal energy conversion efficiency (85.1%). This study provides new ways to convert waste low–value biomass materials into high-value renewable energy (solar-thermal-electricity) with long-term reusability via a simple and green technology. These are tremendous economic benefits in the thermal energy storage sectors.

To improve the utilization efficiency of solar energy, Ag@Fe3O4 core-shell nanoparticles with strong light absorption capacity were prepared, and showed good photothermal and photoelectric properties. Synergistic effects of nanoparticle concentration, light intensity and metal foam on photothermal and photoelectric properties were studied. The results showed that the SPR effect of nanoparticles improves the light absorption ability. Compared with deionized water, the addition of nanoparticles can increase the temperature by 6.10% and the power generation efficiency by 18.75%. When the concentration exceeds a certain range, the increase in concentration no longer plays a positive role. The increase of light intensity can increase the voltage and output power by up to 45.28% and 44.78%. However, it will increase the temperature gradient between the surface and the bottom of the nanofluids, increase the heat loss, and lead to a decrease in power generation efficiency. The synergistic effect of nanoparticles and metal foam can better improve the photothermal performance. The addition of metal foam can increase the power generation efficiency by 5.65%.

To reap in the full benefit of high-efficiency solar cells and modules, the quality of the polymer encapsulant and backsheet (BS) materials is essential. Recent field studies show that early degrading backsheets cause safety issues and inverter shutdowns, resulting in yield losses. The dynamic development of degradation is important but is rarely studied because of the lack of proper datasets with meaningful and sufficient data. We studied inverter data of solar panels with a combined capacity of about 1 MWp for more than nine years including ground impedance (GI), and we labelled BS-types using our in-house identification method. Every inverter was connected to modules with exclusively a single BS-type, namely three-multilayer BSs denoted by their outer air layer: PA (polyamide), FC (fluorinated coating), and PVDF (polyvinylidene fluoride). We present, for the first time, an analysis of the degradation dynamics of GI, using a trained Gaussian Process Regression model. Using this model, we derived key degradation parameters, namely GI loss rates and time points for the onset of degradation. We found that PVDF BSs are associated with very low GI loss rates, while loss rates for PA are threefold higher with an onset at 6.6 year of operation for PA. FC BS-related loss rates were humidity dependent and two times higher those of PA; the onset was determined at 4.9 year of operation.

Improving the conversion efficiency of n-TOPCon solar cell is still a hot topic. The selective poly-Si based passivating contacts (Poly-SEs) are ideal candidates for reducing the parasitic absorption and contact resistivity of n-type silicon solar cells and for providing better current collection. In this work, we used LPCVD and the POCl3 tube furnace diffusion methods to fabricate the selective poly-Si based passivating contacts, and studied the influences of key process parameters of the SiOx layer formation process (the oxidation duration (toxidation) and the constant pressure duration (tpressure)), and POCl3 tube diffusion process parameters (the POCl3-N2 carrier gas flow rate at the deposition, deposition temperature, drive-in temperature) on the n+-poly-Si profiles, recombination current density (J0), contact resistivity (ρc) of n-TOPCon solar cells. The results showed that the toxidation and tpressure had a significant impact on J0 and ρc which were mainly related to the distribution number of O and Si4+ content on the growth of the SiOx layer. And the influence of the drive-in temperature of phosphorus (P) diffusion process on J0 value is stronger than that of the deposition temperature, which was mainly related to the chemical passivation of SiOx layer induced by P-indiffusion into Si at high temperature. The reduction in the thickness of poly-Si from 110 nm to 30 nm led to an increase in the short-circuit current density (Jsc) per nanometer of ∼0.0093 mA/cm2 per nm. The Poly-SEs were fabricated by 3D printing mask technology and secondary LPCVD/phosphorus diffusion with J0, n+ ≈ 5 fA/cm2 (n+-poly-Si layer ≈ 50 nm) and J0, metal,n++ ≈ 73.8 fA/cm2 (n++-poly-Si layer ≈ 110 nm), and the efficiency was improved by 0.12% owing to the increase in Jsc value of 0.28 mA/cm2. After optimizing the passivation process, the industrial-grade TOPCon bifacial cells reached an efficiency (Eff), Voc, Jsc, and FF values as high as 25.4%, 721 mV, 42.2 mA/cm2, and 83.5%, respectively.

A long operational lifetime is required for the use of solar cells in real-life photovoltaic applications. The optimization of operational lifetimes is achieved through understanding the inherent degradation phenomena in solar cells. In this study, graphene/Si Schottky-junction solar cells were produced, utilizing liquid-phase-exfoliated graphene as an active surface. The operational and interface stability of these solar cells over a period of 5 years in ambient conditions (following ISOS-D protocols: dark storage/shelf life) was examined, and the origin of their degradation was reported. It was found that the dominant degradation mechanism could be attributed to the degradation of silver contacts. This was indicated by a decrease in shunt resistance, an increase in the ideality factor (due to a higher carrier recombination), and a constant defect density in graphene films for up to 4 years. Measurements across the solar cell's active area during the 5-year period revealed neither significant spatial inhomogeneity, nor shunt channel defects.

This study investigates effects of the modification of NiOx hole-selective contacts (HSCs) with self-assembled monolayers (SAMs), [2-(9H-carbazol-9-yl) ethyl]phosphonic acid (2PACz), on the characteristics of perovskite solar cells, used for perovskite–silicon tandem cells. After the NiOx layers were fabricated by RF sputtering, the 2PACz modification was performed by the spin-coating of a 2PACz solution and subsequent annealing at 100 °C for 10 min. The 2PACz-modified NiOx layer improved the solar cells' open-circuit voltage and short-circuit current density. Photoelectron yield spectroscopy measurements imply that the 2PACz monolayers increase the work function of the NiOx HSCs, thereby enhancing field-effect passivation at the perovskite–HSC interface. Density functional theory calculations and electron spin resonance measurements indicate that an increase in the work function results from a vacuum level shift due to the electric dipole moment of 2PACz molecules and formation of space-charge region at the NiOx–2PACz interface. The performance improvement is explained as a result of enhanced field-effect passivation caused by the vacuum level shift and thus the increase in the work function. These findings, which clarify SAM modification effects of HSCs on solar-cells’ performance, can contribute to the development of highly efficient and reliable perovskite–silicon tandem solar cells.