Sunlight Research Articles

Characteristics and Applications of Graphitic Carbon Nitride Nanocomposite

Graphitic carbon nitride (g-C3N4) has attracted much attention due to their diverse properties such as optical properties, unique structure, morphology modify, chemical stability, and inexpensive and facile synthesis. With these special properties, aromatic tri-s-triazine carbon nitrides show broad interdisciplinary potential for a variety of applications. One of the issues with g-C3N4 is the recombination of photogenerated electron-hole pairs. It is difficult for single-component photocatalysts to harvest a large portion of the solar spectrum while possessing adequate space charge separation and efficient redox capability. Building g-C3N4-based doped or heterostructures can induce electron-hole pair separation through charge transfer across the interface. We systematically analyzed and discussed the recent research developments of g-C3N4 nanocomposites, including the preparation of g-C3N4, characterization of microstructure, various modifications, energy-related and applications. Finally, we proposed the current challenges and promising future prospects of g-C3N4-based materials.

Ultrafast Modulations in Stellar, Solar and Galactic Spectra: Dark Matter and Numerical Ghosts, Stellar Flares and SETI

Background: - From new results presented in the literature we discuss the hypothesis, presented in an our previous work, that the ultrafast periodic spectral modulations at fS=0.607±0.08 THz found in the spectra of 236 stars of the Sloan Digital Sky Survey (SDSS) were due to oscillations induced by dark matter (DM) cores in their centers that behave as oscillating boson stars. Two other frequencies were found by Borra in the redshift-corrected SDSS galactic spectra, f1,G=9.71−0.19+0.20 THz and f2,G=9.17−0.16+0.18 THz; the latter was then shown by Hippke to be a spurious frequency introduced by the data analysis procedure. Results: - Within the experimental errors, the frequency f1,G is the beating of the two frequencies, the spurious one, f2,G and fS that was also independently detected in a real solar spectrum, but not in the Kurucz’s artificial solar spectrum by Hippke, suggesting that fS could actually be a real frequency. Independent SETI observations by Isaacson et al., taken at different epochs, of four of these 236 stars could not confirm with high confidence - without completely excluding - the presence of fS in their power spectra and with the same power initially observed. Instead, the radio SETI deep-learning analysis with artificial intelligence (AI) gave an indirect confirmation of the presence of fS through the detection of a narrowband Doppler drifting of the observed radio signals in two stars, over a sample of 7 with a high S/N. These two stars belong to the set of the 236 SDSS stars. Numerical simulations confirm that this drifting can be due to frequency and phase modulation in time of the observed frequencies (1.3–1.7 GHz) with fS. Conclusions: - Assuming the DM hypothesis, the upper mass limit of the axion-like DM particle is ma≃2.4×103μeV, in agreement with the results from the gamma ray burst GRB221009A, laser interferometry experiments, suggesting new physics with additional axion-like particle fields for the muon g-2 anomaly.

Biosynthesis of TiO2 nano particles by using Rosemary (Rosmarinus officinalis) leaf extracts and its application for crystal dye degradation under sunlight

Titanium dioxide (TiO2) nanoparticles were prepared through Rosmarinus-officinalis leaf extracts at 90 and 200°C. In this research, the degradations of methylene blues by using TiO2 nanoparticles Sun light radiations were studied. The synthesized materials were characterized using XRDs, UV-Vis, PL, SEM, TEM, EDS and XPS. The results displayed that bio-synthesis temperatures intrude the shapes and sizes of TiO2 nanoparticles. For TiO2-90, micrographs show separable crystalline with irregular morphologies and agglomerate cubic particles. For the other TiO2-200 sample, SEM and TEM micro-imaging shows crumbly agglomerated cubic structures. The XRD shows that the intense peaks observed at angles of 25.37°, 37.19°, 47.81° and 53.89° confirming a highly crystalline oriented as (004), (200), and (105) planes respectively. The optical properties of TiO2 nanoparticles synthesized were conveyed by PL and UV-Vis. The energy band gap calculated was 3.0 eV for both samples; that indicates heating temperature didn’t influence the band gap of the samples. The elemental composition Ti and O2 is shown by EDS and XPS. Photo-catalytic experiments discovered that TiO2-90 nanoparticles were well-organized in photo-degradations of MB, likened to TiO2-200. The great activities of TiO2-90 were because of better physicochemical characteristics associated with TiO2-200 effectively degrading MB under photo-light. Photo-degradations of dye under sunlight as plentifully obtainable energy sources by TiO2, synthesized by simpler techniques, can be hopeful to grow an eco-friendly and economical process.

Incorporation of zinc oxide and cobalt doped zinc oxide nano-rods in commercial sunscreen sample to optimize its UV-ray absorption

In the last two decades, the ozone layer in the atmosphere has been depleted, and the sun rays are now more harmful to human skin because they no longer filters it completely. Long-term exposure to harmful ultraviolet rays (UV-rays), which have wavelengths between 220 nm and 380 nm, causes catastrophic damage to skin cells. Sunscreens are therefore absolutely necessary to protect the skin. The co-precipitation method was used to synthesize both pure and cobalt-doped zinc oxide nano structures. In sunscreens, these nanostructures serve as a UV filter. The obtained nano structures have been characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). The ability of a sunscreen sample containing nano structures to yield results for a period of various hours at different temperatures (20 °C, 30 °C, and 50 °C) has been tested. According to XRD results, prepared samples exhibits hexagonal wurtzite crystalline structures and are of 22 nm in size for pure zinc oxide and 20 nm in size for cobalt- doped zinc oxide. SEM was used to find morphologies, i.e., nano rods (NRs) at 200 nm and 2 μm. DRS provided evidence of sunscreen’s endurance, with a 97% absorption of UV-rays at 50 °C for up to 6 h when incorporated with NRs. In order to boost UV-ray absorption in sunscreen, nanotechnology has been successfully applied.

Solar photospheric spectrum microvariability

Solar photospheric spectrum microvariability

Effects of Photoperiod and Light Quality on Germination and Growth of Camellia sinensis 'HuangKui'.

Light, as a critical environmental factor, plays a pivotal role in photosynthesis, ultimately influencing the timing of bud flush in tea plants. However, the synergistic effects of different photoperiods and light qualities on the timing of bud flush in the albino tea cultivar 'HuangKui' (later germination variety) remain unknown. Thus, the objective of this study was to investigate the effects of different photoperiods (12L/12D, 14L/10D, 16L/8D, and 18L/6D, where L = the number of daylight hours and D = the number of hours of darkness) and ratios of red (R) to blue (B) light (R/B 1:1, R/B 1:2, R/B 1:3, and R/B 2:1) on the germination and growth of the albino tea variety 'HuangKui'. In our study, we examined how different photoperiods and red light and blue light affected tea germination and growth by investigating the timing of bud flush, photosynthesis, chlorophyll content, and growth indicators. First, our study showed that 'HuangKui' germinated 4 days, 2 days, and 1 day earlier under the 16L/8D photoperiod at the one bud and one leaf period compared with plants cultivated under the 12L/12D, 14L/10D, and 18L/6D photoperiods under light simulating the solar spectrum. Also, the growth of 'HuangKui' was maximumly promoted under the 16L/8D photoperiod treatment. Additionally, the earliest germination of 'HuangKui' was observed for the 16L/8D photoperiod under the R/B 2:1 (red/blue) treatment compared with the other treatments. Moreover, the greatest plant height, length of the new shoots, and new leaf areas were detected in the albino tea variety 'HuangKui' under R/B 2:1. Moreover, the contents of auxin (indole acetic acid, IAA) and trans-zeatin (tZ) under R/B 2:1 were significantly higher than those under the R/B 1:1 and control treatments with the 16L/8D photoperiod. Additionally, the auxin-related expression levels of CsIAA13, CsGH3.1, CsAUX1, and CsARF2 under the R/B 2:1 treatment were significantly higher than those in the control. The expression of CsARR-B, a positive regulator of cytokinin-related genes, was significantly higher under the R/B 2:1 treatment than under the control treatment, while the opposite result was found for the expression of the negative regulator CsARR-A. Therefore, the R/B 2:1 treatment with the 16L/8D photoperiod was an appropriate means of timing the bud flush for the albino tea variety 'HuangKui', which may be related to IAA or tZ signal transduction. In conclusion, our research offers a novel lighting strategy that promotes the germination and growth of albino tea cultivars.

Exploring the potential of Te@Carbon–Rich hybrid nanocables/PDMS composites for Solar–Driven thermoelectric power generation

This study pioneers the integration of Te@carbon–rich hybrid nanocables (NCs) as fillers into a polydimethylsiloxane (PDMS) matrix, yielding a composite tailored for efficient solar–driven power generation. The distinctive synergy between Te NWs and the carbonaceous shell within the NCs could play a crucial role in efficiently enhancing photo–assisted thermoelectric power generation. When subjected to 1 sun light illumination, the pure PDMS film displayed an output voltage of 54.8 mV and a current of 17.2 mA. However, the introduction of carbonaceous nanospheres (NSs) into PDMS resulted in improved performance, with the NSs/PDMS composite achieving voltage values of 71.7 mV and current values of 22.4 mA, corresponding to a power generation of ∼1600 μW. Notably, the addition of nanocables (NCs) significantly enhanced power generation, with the NCs/PDMS composite reaching maximum values of 94.3 mV for voltage and 33.4 mA for current, resulting in a power output of ∼3150 μW. This enhancement stems from the increased photothermal performance facilitated by the collaboration of two photothermal mechanisms: non–radiative recombination (Te NWs core) and lattice relaxation (carbonaceous shell). These NCs/PDMS flexible composites, leveraging Te, C, and PDMS benefits, show promise for solar–driven power generation, offering a path to a sustainable future.

Upright Pyramid Surface Textures for Light Trapping and MoOx Layer in Ultrathin Crystalline Silicon Solar Cells

In this work, ray tracing is used to investigate the optical characteristics of various surface structures in ultrathin crystalline silicon (c-Si) for solar cells. Ultrathin c-Si with a thickness of 20 μm is used as the substrate. The light trapping includes front upright pyramids with a molybdenum oxides (MoOx) anti-reflection (AR) layer. Planar ultrathin c-Si (without a MoOx AR layer and upright pyramids) is used as a reference. The wafer ray tracer was developed by a photovoltaic (PV) lighthouse to model the MoOx AR layer to reduce the front surface reflectance and impacts of the AR layer on ultrathin Si solar cells. The optical properties are calculated on the AM1.5 global solar energy spectrum across the 200–1200 nm wavelength region. From the absorbance profile, the photogenerated current density (Jph) in the substrate is also calculated with various surface structures. The front upright pyramids with the MoOx layer result in the largest absorbance enhancement due to the enhanced light scattering by the pyramids and MoOx AR layer. The Jph of 37.41 mA/cm2 is improved when compared to the planar ultrathin c-Si reference. This study is significant as it illustrates the potential of ultrathin c-Si as a promising PV module technology in the future.

Tunable broadband absorbers with ultra-high thermal emissivity for the mxene/ti-based metamaterial

Solar energy was widely used in lots of fields, such as the heat pump technology, seawater desalination, wastewater treatment and photoelectric detection, where efficient use of solar energy was always the goal pursued by mankind. In the work, we proposed a simple and efficient MXene/Ti-based metamaterial absorber and investigated the optical and thermal radiation properties by using the finite-difference time-domain (FDTD) method. The results showed that the average absorption of the MXene/Ti-based metamaterial absorber was higher than 97.6 % from 400 nm to 1600 nm, the maximum absorption reached 99.6 %, and the solar spectrum weighted absorption was close to 98.5 %, and the physical mechanism of the broadband absorption was also explored by theoretical analysis. Compared with the latest reported absorbers, the MXene/Ti-based metamaterial not only had the advantages of low energy loss, high efficiency, and good thermal stability, but also its broadband absorption showed excellent robustness to structural parameters. Moreover, a 75° wide-angle absorption was obtained for the MXene/Ti-based metamaterial, which was independent of polarization. Last but not least, the MXene/Ti-based metamaterial achieved an ultra-high thermal emissivity of 98.3 % at 1600 K, which matched the blackbody radiation curves at 1600 K. These studies had significant implications for catalysis, solar photovoltaics, photovoltaic conversion and other fields.

Host sensitized down conversion emission in KSrVO4:Yb3+− A potential thermally stable phosphor for solar cell applications

This work reports the successful synthesis of an efficient near infra-red (NIR) emitting KSrVO4:Yb3+ phosphor using the combustion method. The X-ray diffraction technique (XRD) confirmed the orthorhombic phase of a material whereas X-ray photoelectron spectroscopy (XPS) analyzed the elemental makeup and chemical states of the phosphor components. Photoluminescence (PL) analysis revealed that the phosphor exhibit superior thermal stability and emit in the NIR region when activated by near-UV light. An upsurge in emission intensity occurs upon the incorporation of Bi3+ as a co-dopant. Using diffuse reflectance spectra (DRS), optical band gap, metallization constant, and refractive index were computed for all ion concentrations in KSr(1-x)VO4:xYb3+ (0 ≤x ≤ 0.06). For the optimized concentration of Yb3+ into the host, numerical values of these parameters were also estimated. The studies reveal that the produced material may be applied as a solar spectrum converter to improve the efficiency of crystalline silicon (c-Si) solar cells.

Molecular Copper(I)-Sensitized Photoanodes for Alcohol Oxidation under Ambient Conditions.

Dye-sensitized photoelectrochemical cells can enable the production of molecules currently accessible through energetically demanding syntheses. Copper(I)-based dyes represent electronically tunable charge transfer and separation systems. Herein, we report a Cu(I)-bisdiimine donor-chromophore-acceptor dye with an absorbance in the visible part of the solar spectrum composed of a phenothiazine electron donor, and dipyrido[3,2-a:2',3'-c]phenazine electron acceptor. This complex is incorporated onto a zinc oxide nanowire semiconductor surface effectively forming a photoanode that is characterized spectroscopically and electrochemically. We investigate the photo-oxidation of hydroquinone, and the photosensitization of 2,2,6,6-tetramethylpiperidine-1-oxyl and N-hydroxyphthalimide for the oxidation of furfuryl alcohol to furfuraldehyde, resulting in near quantitative conversions, with poor selectivity to the alcohol.

Geometrical optimization of solar venetian blinds in residential buildings to improve the economic costs of the building and the visual comfort of the residents using the NSGA-II algorithm

The entering sunlight from the building's windows mainly affects the heating and visual comfort of the occupants. The applications of Venetian blinds are a solution to improve the heating and visual comfort of the occupants. However, reducing the sunlight that enters the space can result in a rise in the building's electricity consumption. While most studies focus on the electricity production of solar panels, present study aims to examine the effect of solar venetian blinds on the indoor visual and thermal comfort of the occupants and optimize their geometry considering different geographical specifications. In the present paper, efforts are made to numerically install solar panels on Venetian blinds and analyze the effect of changing the geometrical parameters of solar Venetian blinds and the building's window dimensions on visual comfort and net electricity. Therefore, the target functions in the present paper are an improvement percentage in the daylight glare index and an improvement percentage in the net electricity costs for the analyzed building. As a result, five cities in Iran that have different climatic conditions are targeted to model the building. EnergyPlus software is employed to conduct the energy-based calculations, and the design variables and target functions are defined using JEPLUS software. The outputs are next inserted in JEPLUS+EA software to process a multi-objective optimization using the NSGA-II algorithm. The results demonstrate that the visual comfort and net electricity can be optimized by ranges of 10–100% and 1.5–10%, respectively. Furthermore, Venetian blinds are proven to have higher reception of sun radiations and better efficiency in southern cities and they can have a more proper performance while being installed for windows of southern building wall.

Improving Asphalt Binder Durability Using Sustainable Materials: A Rheological and Chemical Analysis of Polymer-, Rubber-, and Epoxy-Modified Asphalt Binders

When exposed to sun radiation and heat, asphalt binders age, resulting in reduced flexibility, cracking, and pavement failure. Given the increasing demands of traffic, environmental concerns, and resource scarcity, highway agencies and researchers are actively seeking solutions that meet performance requirements and demonstrate awareness of using non-renewable resources. Epoxy asphalt (EA) promotes sustainability concepts due to its production at significantly lower mixing and compaction temperatures, enhanced durability, improved serviceability, reduced maintenance needs, and successful recycling and reuse in hot asphalt mixtures. Crumb rubber, a widely recognized recycled waste tire material, is considered a viable option for promoting sustainability and enhancing asphalt binder properties. This study aims to enhance the durability and long-term performance of asphalt binders by utilizing sustainable materials. Six types of asphalt binders were employed: PG 67-22 base asphalt binder; styrene–butadiene–styrene (SBS)-modified PG 76-22 and PG 88-22H (3.5% and 7.0% dosage rates, respectively); a hybrid PG 76-22CS-modified asphalt binder prepared with SBS and crumb rubber modifiers; and 25EAB and 50EAB epoxy-modified asphalt binders prepared at 25 and 50% dosage rates, respectively. Results indicate that the sustainable asphalt binders PG 76-22CS, 25EAB, and 50EAB demonstrated comparable or superior performance compared to SBS-modified asphalt binders, as measured by rutting and fatigue factors. Additionally, epoxy asphalt binders had better anti-aging and cracking resistance, as shown by the outcomes of Fourier-transform infrared spectroscopy and linear amplitude sweep tests, respectively. This study contributes valuable insights into the potential of sustainable materials to enhance the overall performance and resilience of asphalt binders.

NiO nanoparticles by thermal decomposition of complex and evaluation of the structural, morphological, and optical properties

An efficient method for the synthesis of metal oxide nanoparticles (NPs) involves the solid-state thermal decomposition of precursor complexes. This study reports on the preparation of nanocrystalline nickel oxide (NiO) through a solid-state thermal decomposition of nickel(II) bis(N-methyl-N-paramethoxyphenyl dithiocarbamate) in a furnace. The novel Ni(II) complex was characterized using various analytical techniques. The single-crystal X-ray structure of the new nickel dithiocarbamate complex, C18H20N2NiO2S4, was determined and it showed a square-planar nickel coordination environment. The CH⋯S intramolecular hydrogen bond in this complex contributes to the planarity of the Nickel coordination environment. The complex underwent thermal decomposition in the air at about 750 °C for varying times of 90, 120, 150, and 180 min, resulting in the production of the oxide. Subsequently, the study explored how varying calcination times influenced the structural, morphological, and optical characteristics of the formed NiO nanoparticles. Face-centered cubic (FCC) structure of NiO NPs was confirmed whose crystallite size increased with an increase in the dwelling time of calcination and has been attributed to the possible coalescence of smaller crystallites to form larger ones. The confirmation of the face-centered cubic (FCC) structure of NiO nanoparticles was established, with the crystallite size observed to increase alongside longer calcination periods. This phenomenon has been linked to the potential amalgamation of smaller crystallites into larger ones. The optical energy bandgap decreased from 4.35 to 3.40 eV with an increase in the calcination time due to the increase in crystallite size occasioned by a longer reaction time from 90 to 180 min. These NPs will be useful as photocatalysts due to their high crystallinity and the capability to absorb within the visible region of the solar spectrum.

Transparent insulating photochromic PU/PTA films for Wide-Spectrum modulated smart windows

Photochromic materials have recently attracted widespread attention in the research of smart windows because they can function without additional devices. In this study, an innovative photochromic thermal insulating hybrid film based on a polyurethane matrix was prepared via a one-pot method, incorporating phosphotungstic acid. The film demonstrates excellent transparency, good mechanical strength, and a significant modulation of the solar spectrum, transitioning from colorless to dark blue under sunlight without the need for additional electron donors. This photochromic behavior is reversible and reproducible without degradation, resulting in a transmittance variation of up to 71 % at 550 nm, which is the most sensitive to the human eye, and more than 50 % modulating performance in 1800 ∼ 2500 nm. In addition, thermal insulation experiments proved that the smart window device prepared by the film could achieve a reduction of 9.3 °C under daylight. Overall, the photochromic films prepared using the one-pot method show good performance involving mechanical strength, efficient photochromic response, broad spectral range modulation, high coloring efficiency and cycling stability, and have promising applications in energy-saving buildings, anti-counterfeiting and smart displays.

Dampening long-period doppler shift oscillations using deep machine learning techniques in the solar network and internetwork

This study aimed to explore the Doppler shift at different wavelengths in the IRIS solar spectrum and analyze the evolution and statistical properties of longitudinal oscillations with damping in chromosphere and transition region bright points (BPs). Understanding the damping mechanism and statistical properties of oscillations in BPs is crucial for gaining insights into the dynamics and energy transport within the solar atmosphere.This study explores the Doppler shift at different wavelengths in the solar spectrum of the Interface Region Imaging Spectrograph (IRIS) and implements a comprehensive consideration of Doppler velocity oscillations in the IRIS channels. This comprehensive consideration reveals a propagating periodic perturbation in a large number of chromosphere and transition region (TR) bright points (BPs). To the best of our knowledge, this is the first investigation of the longitudinal oscillations with damping in BPs using comprehensive consideration of the Doppler velocity at various wavelengths. The phenomena of attenuation in the red and blue Doppler shifts of the solar wavelength range were seen several times during the experiments. We utilized deep learning techniques to examine the statistical properties of damping in network and internetwork BPs, as well as active, quiet areas, and coronal hole areas. Our results revealed varying damping rates across different regions, with 80% of network BPs exhibiting damping in quiet areas and 72% in coronal hole areas. In active areas, the figure approached 33%. For internetwork BPs, the values were 65%, 54%, and 63% for quiet areas, coronal hole areas, and active regions, respectively. The damping rate in active regions is twice as high at Internetwork’s BPs. The damping components in this study were computed, and the findings show that the damping at all points is underdamped. The observed damping process suggests the propagation and leaking of energetic waves out of TR bright points, potentially contributing to the energy transport from the bright magnetic footpoints to the upper chromosphere, transition region, and corona.

Submerged nanoporous anodized alumina structure for solar-powered desalination.

Development of nanoporous structures utilizing a single step of anodization technique is well recognized as a cost-effective and straightforward approach for several applications. In the current work, anodized alumina was developed with nanoporous structure by utilizing oxalic acid as an electrolyte with a continuous voltage of 40 V. The formed nanoporous structure was subjected to desalination application because of its high absorbance of broadband solar spectrum energy. The desalination setup consists of two solar stills namely conventional and modified. The developed structure is placed in the modified still to examine its performance. It was observed that the structure distributing heat to surrounding water by absorbing photon energy from the sun through the nanopores and giving an efficient pathway to the water vapours for developing effective desalination. The nanoporous structure having ~ 45 nm average diameter. Furthermore, the band gap energy of nanoporous structure was found to be ~ 2.5 eV (absorption spectrum fitting) and ~ 2.8 eV (Tauc plot). The nanoporous structure possess the visible light spectra in solar region which helps the band gaps of nanoporous structure to provide an additional supply of energy for generating more water to evaporate. Moreover, the Urbach energy of the structure is 0.5 eV which reveals less defects in the modified still. The overall distillate yield of modified still was increased to 21% in contrast to conventional. Water quality analysis was also carried out before and after the desalination experiments, and the results were within acceptable limits set by World Health Organization (WHO).

Materials Advances in Photocatalytic Solar Hydrogen Production: Integrating Systems and Economics for a Sustainable Future.

Photocatalytic solar hydrogen generation, encompassing both overall water splitting and organic reforming, presents a promising avenue for green hydrogen production. This technology holds the potential for reduced capital costs in comparison to competing methods like photovoltaic-electrocatalysis and photoelectrocatalysis, owing to its simplicity and fewer auxiliary components. However, the current solar-to-hydrogen efficiency of photocatalytic solar hydrogen production has predominantly remained low at ≈1-2% or lower, mainly due to curtailed access to the entire solar spectrum, thus impeding practical application of photocatalytic solar hydrogen production. This review offers an integrated, multidisciplinary perspective on photocatalytic solar hydrogen production. Specifically, the review presents the existing approaches in photocatalyst and system designs aimed at significantly boosting the solar-to-hydrogen efficiency, while also considering factors of cost and scalability of each approach. In-depth discussions extending beyond the efficacy of material and system design strategies are particularly vital to identify potential hurdles in translating photocatalysis research to large-scale applications. Ultimately, this review aims to provide understanding and perspective of feasible pathways for commercializing photocatalytic solar hydrogen production technology, considering both engineering and economic standpoints.

Silicon / Perovskite Tandem Solar Cells with Reverse Bias Stability down to -40V. Unveiling the Role of Electrical and Optical Design.

The reverse bias stability is a key concern for the commercialization and reliability of halide perovskite photovoltaics. Here, the robustness of perovskite-silicon tandem solar cells to reverse bias electrical degradation down to -40V is investigated. The two-terminal tandem configuration, with the perovskite coupled to silicon, can improve the solar cell resistance to severe negative voltages when the tandem device is properly designed. While perovskite cells typically exhibit early reverse bias breakdown voltages, the serial connection with silicon cells with large shunt resistances and high voltage breakdown limits their negative polarization and prevent the passage of large current densities when reverse biased. The importance of careful optical design is illustrated, with bottom-limited conditions required to prevent the perovskite topcell from exploring its own breakdown. This aspect is of great importance in the case of partial shading events when the solar spectrum is richer in the IR components than the standard AM1.5G. Notably, 100% of efficiency retained after polarization at -40V in different stressing conditions is observed. The results presented suggest that standard industrial bypass diode schemes may be compatible with silicon/perovskite tandem photovoltaics and provide new guidelines for the standardization of the stressing protocols.

Efficiency enhancement of solar cell using mirror concentrator

This research is done to find out a method by which the efficiency of a solar cell can be increased by using mirror concentrator to get a higher power and optimum efficiency. At first the sun lights are incident on the mirror concentrator made of plane glass and then the reflected rays are incident to the solar cell. Flat mirror concentrator (FMC) has been used to increase the incident irradiance on solar panel system by concentrating the sun light ray on it and then to improve the cell performance. A comparison is made for the same PV solar panel systems using single and triple flat mirror concentrator. It is a beneficial and important theory of solar power plant sector. It can be used in household and any kind of industrial area. The FMC consists of two flat mirrors made of glass, with dimensions (170cm × 80cm) enclosed by aluminum frame and inclined to an angle 55° with a solar panel (160cm × 120cm) tilted at 45° from the horizon. The results indicated that when the concentrator is used with the solar panel the efficiency increased by a factor of 4.52% to 11.34%. So, the increase in efficiency of the solar cell is 6.82%.