Increase In Efficiency Of Solar Cells Research Articles

Using ZnO/PMMA Nanocomposite Coating to Improve the Polycrystalline Solar Cell in Hot Weather Conditions

Solar energy is the most significant future energy source as the world keeps working to minimize emissions caused by the use of fossil fuels. The most popular method for transforming sunlight into electrical energy is the photovoltaic solar cell (PV). The main two problems with PV solar cells highlighted in this paper are the high solar cell surface temperature and the high reflection light of PV solar cells. Because each 1 °C increase in surface temperature reduces efficiency by 0.45%, and approximately 35% of total sunlight reflected in crystalline silicon solar cells. In this experimental work, the sol-gel process was used to prepare different concentrations of zinc oxide/polymethyl methacrylate (ZnO/PMMA) nanocomposite coatings and apply them to the top side of the polycrystalline solar cell in order to increase the solar cell efficiency. The results demonstrate a maximum temperature drop of 8.6 ºC and light reflection reduced up to 5.6%, so this led to an increase in solar cell efficiency from (11.33%) to (15.22%), where the results of the electrical properties after one hour (test time) showed that the uncoated cell was (ISC = 0.33 A, VOC = 0.38 V, and Pmax = 97 mW), while the results of the coated cell with the best concentration (3.875 wt%) were (ISC = 0.36 A, VOC = 0.43 V, and Pmax = 130 mW).

Towards high-efficiency Al-BSF c-Si solar cell with both superior omnidirectional and electrical performance by modulating the tilt angle of quasi-periodic inverted pyramid arrays

Seeking efficient light trapping structures with both superior omnidirectional and electrical performance is always on the way for increasing electrical energy output of c -Si solar cell over a wide range of light incident angle (θ). Here, tile angle (δ) of quasi-periodic structure arrays is systematically modulated from 35.9° to 72.8° on diamond-wire-sawn (DWS) c -Si by a simple and cost-effective Cu and Ni co-assisted chemical etching way followed by a post treatment. Interestingly, compared with the conventional micro pyramid (MP), the optimized inverted pyramid (IP) like arrays with a δ of 64° possess both lower light reflectance and carrier recombination, leading to a corresponding solar cell with a higher efficiency (∼19.67%) than that of MP based counterpart (∼19.31%). Moreover, during the increase of θ, the external quantum efficiency (EQE) of 64° IP based cell drops much more slowly than that of MP based one by properly adjusting the relative position of the structure arrays and incident light, indicating its omnidirectional property. Simultaneously, a maximum relative enhancement of electrical output power approaching ∼5.8% in the θ range of −90°–90° is achieved on 64° IP based cell compared to the MP based one, the mechanism behind which is further explained by optical simulation. The above finds pave a new way to increase the electrical energy output in a simple and cost-effective way. • Tilt angle control of quasi-periodic IP was achieved by varying Cu and Ni ratio. • 0.36% absolute increase in solar cell efficiency was made based on 64° IP. • ∼5.8% relative increase of output power was achieved on 64° IP based cell. • Mechanism behind omnidirectional performance was explained by optical simulation.

Optimum heat spreader size for producing maximum net power from high‐concentration photovoltaic systems

The present study introduces an analytical approach for predicting net power for high-concentrating photovoltaic systems (HCPV). Wind speed, surface radiation, and size of the backplate, which acts as a heat spreader, were found to be of high impact in increasing solar cell efficiency and maximum produced power. The efficiency increased by 5% as the wind shifted from light air (0.5 m/s) to fresh breeze (10 m/s). Also, it increased by 1.64% as the aluminium backplate shifted from a shiny (ɛ = 0) to a dark (ɛ = 1) surface. Furthermore, increasing heat-spreader length or wind velocity caused a logarithmic increase in solar cell efficiency. On the other hand, both parameters caused an exponential increase in consumed power due to the operation of a tracking system. Thus, optimal values of heat-spreader length at which maximum net power is produced exist. A case study based on the annual average values of the hourly-basis meteorological data for the period 2015 to 2018 for two cities in Saudi Arabia was conducted. It was found that the size of the heat spreader could be reduced by 36% for concentration ratio up to 2000 while concurrently increasing the net power by 2.6% and 6% for the systems built in Riyadh and Dammam, respectively.

Modeling and Experimental Analysis of Photovoltaic Parameters of GaInP/GaAs Dual Junction p–i–n Solar Cell

In this study, the modeling and experimental analysis of photovoltaic parameters of the GaInP/GaAs dual–junction (DJ) p–i–n solar cell structure were examined. The design of the GaInP/GaAs DJ p–i–n solar cell structure was done with the drift–diffusion model (DDM), and this structure was grown with the molecular beam epitaxy (MBE) system. The fundamental parameters (open–circuit voltage ( $${V}_{\mathrm{OC}}$$ ), short–circuit current density ( $${J}_{\mathrm{SC}}$$ ), fill factor ( $$\mathrm{FF}$$ ), and energy conversion efficiency ( $$\eta$$ )) of these structures were determined by both modeling and the current–voltage experimental measurements. All electrical output parameters of the GaInP/GaAs DJ p–i–n solar cells obtained from modeling and experimental were compared. An increase in solar cell efficiency was observed with the integration of the i–layer.

Performance of perovskite solar cell coated with graphene oxide as hole transport layer

Organic metal halide perovskite has recently shown great potential for applications, as it has the advantages of low cost, excellent photoelectric properties, and high power conversion efficiency. The Hole Transport Material (HTM) is one of the most critical components in Perovskite Solar Cells (PSC). It has the function of optimizing the interface, adjusting the energy compatibility, and obtaining higher PCE. The inorganic p-type semiconductor is an alternative HTM due to its chemical stability, higher mobility, increased transparency in the visible region, and general valence band energy level (VB). Here we report the use of the Graphene Oxide (GO) layer as a Hole Transport Layer (HTL) to improve the perovskite solar cells' performance. The crystal structure and thickness of GO significantly affect the increase in solar cell efficiency. This perovskite film must show a high degree of crystallinity. The configuration of the perovskite material is FTO/NiO/GO/CH3NH3PbI3/ZnO/Ag. GO as a Hole Transport Layer can increase positively charged electrons' mobility to improve current and voltage. As a blocking layer that can prevent recombination. The GO can make the perovskite interface layer with smoother holes, and molecular uniformity occurs to reduce recombination. The method used in this study is by using spin coating. In the spin-coating process, the GO layer is coated on top of NiO with variations in the rotation of 700 rpm, 800 rpm, 900 rpm, 1,000 rpm, and 1,500 rpm. The procedure formed different thicknesses from 332.5 nm, 314.7 nm, 256.4 nm, 227.4 to 204.5 nm. The results obtained at a thickness of 227.4 nm reached the optimum efficiency, namely 15,3 %. Thus, the GO material as a Hole Transport Layer can support solar cell performance improvement by not being too thick and thin

Improving the voltage of GaAs solar cells with In0.4Ga0.6As nanostructures

The fundamental reason for the decrease in solar cell (SC) voltage when introducing nanostructures has been found. It consists in the fact that recombination redistributes between nanostructures and bulk GaAs. It has been shown that, by changing the position of the nanostructure medium in p–i–n GaAs SCs, it is possible to partially suppress recombination and improve voltage while maintaining the increase in short-circuit current. The decrease of recombination via nanostructures provides an increase in SC efficiency from 19.87% to 21.94%.

Facile synthesis of Cr doped hierarchical ZnO nano-structures for enhanced photovoltaic performance

Transition metal doped ZnO has been widely used in various research areas such as optoelectronics, chemical sensors, solar cells and photo catalysts. Herein, we fabricated Cr-doped ZnO nanospheres by a facile solvothermal treatment for enhanced photovoltaic performance. A systematic study of the structural and optical properties of Cr doped ZnO were investigated by scanning electron microscopy (SEM), X-ray diffraction technique (XRD), Ultra violet-Visible spectroscopy (UV–Vis) respectively. XRD patterns confirm that the samples have hexagonal (wurtzite) structure with no additional peaks, which suggests that Cr ions replaces the regular Zn sites in the ZnO crystal structure. Furthermore, doped ZnO nanospheres were employed in the hybrid solar cells in combination with P3HT and gave better current densities than their corresponding undoped counterparts. The increase in solar cell efficiency of doped ZnO nanospheres is solely due to the improvement in the charge separation efficiency in the 4% Cr doped ZnO nanospheres. Optoelectronic analysis of the Cr doped ZnO hybrid solar cell showed comparable results of JSC −3.7 (mAcm−2), VOC 0.44 (V), Fill Factor 0.49 and Efficiency (ƞ) 0.79 (%). The enhanced photovoltaic activity of the Cr doped hierarchical ZnO nanostructures provides an interesting grounds for the design and enhancement of the low cost, feasible synthesis of photovoltaic nanostructure materials.

Effect of solar cell efficiency and flight condition on optimal flight control and energy performance for Z-shaped wing stratospheric solar aircraft

The parameters of solar cell efficiency, flight date of year, latitude and sun elevation angle are important to energy conversion of solar cells, which affect optimal flight control and energy performance of Z-shaped solar aircraft. This work is mainly focusing on studying the effect of varying these parameters on optimum attitude planning, optimum wing morphing control and maximum net energy input for Z-shaped solar aircraft. This study shows that, with higher solar cell efficiency, the solar aircraft prefers to more daylight hours configured as Z-shaped wing, larger morphing angle and larger angle between projection of sunlight and wingspan axis, which enhances to achieve more net power input. For the middle and high latitudes in winter with low sun elevation angles, the Z-shaped solar aircraft tends to large morphing angles and small angles between projection of sunlight and wingspan axis. For the low and middle latitudes of the other seasons with high sun elevation angles, it prefers to small morphing angles to make its central wing totally expose to the sunlight, and orient flight attitude to make the projection of sunlight coincide with wingspan axis. Moreover, the research on the impact of solar cell efficiency shows that, compared with the planar wing, the optimal Z-shaped wing is more effective to improve energy margin and extend perpetual flight days with the same increase of solar cell efficiency. The results can provide valuable engineering reference on optimum wing morphing control and optimum attitude planning for Z-shaped stratospheric solar aircraft.

Study of Si Nanowires Produced by Metal-Assisted Chemical Etching as a Light-Trapping Material in n-type c-Si Solar Cells.

Si nanowires (SiNWs) produced by metal-assisted chemical etching on n-type Si were investigated for their use as a light-trapping material in c-Si solar cells. The nanowires were fabricated before junction formation (on a lightly doped Si substrate) so that their core was bulk and nonporous. The above fabrication process was implemented in solar cell fabrication. The SiNW reflectivity was tested at different steps of solar cell processing and found to be lower than that of conventional random pyramids used in c-Si solar cells. Contact formation on the front side of the cell was investigated by considering metal deposition either directly on the nanowires or on bulk areas in between the nanowire areas. The superiority of this second case was demonstrated. Three different Si nanowire lengths were investigated, namely, 0.5, 1, and 1.5 μm, the case of 1 μm giving better results in terms of solar cell characteristics and external quantum efficiency. The electronic quality of the Si nanowire surface was investigated using the corresponding metal-oxide-semiconductor capacitors with atomic-layer-deposited alumina dielectric. Successful reduction of surface recombination centers at the large Si nanowire surface was achieved by reducing structural defects at their surface through a specific chemical treatment. Finally, using the determined optimized conditions for Si nanowire formation, chemical cleaning, and process implementation in solar cell fabrication, we demonstrated ∼45% increase in solar cell efficiency with 1 μm SiNWs compared to that from a flat reference cell processed under similar conditions. The above study was made on test solar cells without surface passivation.

Rubidium segregation at random grain boundaries in Cu(In,Ga)Se2 absorbers

Solar cells based on Cu(In,Ga)Se2 absorbers are the most efficient ones among all thin film photovoltaics. The current world record efficiency was attained by applying a rubidium fluoride (RbF) post deposition treatment (PDT) to the absorber. However, it is still not clear why the introduced Rb improves the solar cell performance. In order to investigate the beneficial effect of Rb, a Cu(In,Ga)Se2 absorber was grown on a Mo coated alkali free substrate and subjected to a RbF PDT. This pure RbF PDT without any additional alkalis from the substrate leads to a strong increase in solar cell efficiency. A thin cross sectional lamella was cut out of the layer stack and investigated via a combination of electron microscopy and high resolution synchrotron based methods. This combinatory approach provides clear indications of the origin of the beneficial effect of Rb. It is evident that Rb agglomerates at detrimental random high angle grain boundaries and dislocation cores, where it likely passivates defects, which would otherwise lead to a recombination of carriers. In contrast, Rb does not agglomerate at benign Σ3 twin boundaries. Additionally, Rb segregates at the interface between the absorber and the MoSe2 layer.

(Invited) Up-Conversion Luminescence of Lanthanide Activated Phosphors

The major problem that limits solar cells’ efficiency is their insensitivity to the whole solar spectrum which is the so-called spectral mismatch. Therefore, several mechanisms have been explored based on photoluminescence (PL) to convert the solar cell spectrum where the spectral response of the solar cell is low to regions where the spectral response of the solar cell is high. Downconversion, up-conversion (UC) and downshifting are some of the mechanisms that may be applied to improve the spectral response. Upconversion nanoparticles (UCNPs) have shown some promising possibilities to be considered in this respect, however, low UC efficiency of UCNPs is still the most severe limitation of their applications. This study reports on the PL and cathodoluminescence (CL) behaviour of different phosphors. The vastly studied lanthanide pairs in UC are Er3+, Ho3+ and Tm3+ with Yb3+ as a sensitizer. Whereas, very few UC studies have been carried out for Yb3+/Tb3+ and Yb3+/Eu3+ pairs. The reason behind these two categories of lanthanides is the way they transfer their energies. Er3+, Ho3+ and Tm3+ co-doped with Yb3+ can be excited by ground state absorption (GSA), excited-state absorption (ESA) and energy transfer up-conversion (ETU) mechanisms whereas the energy transfer from Yb3+ to Tb3+/Eu3+ is due to co-operative energy transfer (CET). Since, Tb3+ and Eu3+ do not have energy levels which can absorb the near infra-red (NIR) light directly, Yb3+ is the best choice in order to obtain the UC luminescence in Tb3+/ Eu3+ doped system. Yb3+ has a single electronic transition within the 4f subshell. The transition from the lower level through ground state absorption can be easily achieved by using NIR radiation, and resulting energy from two or more excited Yb3+ ions can be utilized in the excitation of a single Tb3+ or Eu3+ ion, for gaining improved UC emission. Doping different host materials with these lanthanide pairs were investigated and tested for possible increase in solar cell efficiency. Power tuneable visible UC and infrared emissions were detected upon excitation with a 980 nm diode laser.

Numerical and Experimental Investigation on a Thermo-Photovoltaic Module for Higher Efficiency Energy Generation

One major problem of solar cells is the decrease in efficiency due to an increase in temperature when operating under constant irradiation of solar energy. The combination of solar cell and a thermoelectric generator is one of the methods proposed to solve this problem. In this paper, the performance of thermo-photovoltaic system is studied experimentally as well as through numerical simulation. In the experimental part, design, manufacture and test of a novel thermo-photovoltaic system assembly are presented. Results of the assembled system showed that with reduction of one degree (Centigrade) in the temperature of solar cell under investigation, and about 0.2 % increase in the efficiency will be obtained in comparison with given efficiency at that specified temperature. The solar cell in a hybrid-assembled system under two cooling conditions (air cooling and water cooling) obtained an efficiency of 8 % and 9.5 %, respectively, while the efficiency of a single cell under the same radiation condition was 6 %. In numerical simulation part, photo-thermoelectric performance of system was analyzed. Two methods for evaluation of thermoelectric performance were used: average properties and finite element method. Results of simulation also demonstrate an increase in solar cell efficiency in the combined system in comparison with that of the single cell configuration.

Influence of Mn-doping on the photocatalytic and solar cell efficiency of CuO nanowires

Pristine copper oxide (CuO) and manganese (Mn) doped CuO nanostructures with different ratios were synthesized via wet chemical method. As-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-rays (EDX), UV–Visible and emission spectroscopy. Further, the doped nanowires were employed in the hybrid solar cells in combination with P3HT and gave better current densities than their corresponding undoped counterparts. The photoactivity of synthesized materials was evaluated by the photocatalytic oxidation of Rhodamine B (RhB). The results showed that the 2% Mn doped CuO photocatalyst is highly photoactive than other corresponding undoped and doped CuO nanowires. The increase in solar cell efficiency and photocatalytic activity of the doped CuO nanowires is solely due to the improvement in the charge separation efficiency in the 2% Mn doped CuO nanowires.

Increase of Solar Cell Efficiency in Graded Band Gap Structure

The photo current-voltage characteristic of a solar cell with graded band gap is calculated numerically based on the drift-diffusion equation and Poisson equation. The calculated efficiency of the CdTe solar cell with p-n junction located in 1μm depth increases remarkably when the band gap of the front n-type layer is graded. The effect is strong for high surface recombination velocity and is remarkable even at: the calculated efficiency increases from 19.6% to 24.3%.

Soot and Nanomaterials Synthesis in the Flame

The general scheme of conversion of hydrocarbon fuels with new experimental data on the formation of fullerenes and graphenes taking into account the pressure effect is proposed for the fuel-rich flames. It is shown that the formation of fullerenes is important to the corresponding spatial orientation of PAH, possible at low pressures. The formation of hydrophobic soot surface on silicon and nickel substrates during combustion of propane-oxygen flame was studied. It is established that the hydrophobic properties are due to the presence of soot particles in the form nanobeads. The photovoltaic properties of solar cells coated by nickel oxide nanoparticles synthesized in counter flow propane-air flame. It is revealed that coated the surface of a silicon solar cell by nickel oxide nanoparticles results in the increase in solar cell efficiency by 3%.

10 cm Diameter Mono Cast Si Growth and its Characterization

To get the optimized condition and ideal furnace structure, we have performed seed cast growth of mono-crystalline Si by using unidirectional solidification furnace. More than 20 ingots of 10 cm diameter and 10 cm height were grown under different growth conditions. The quality of ingots was characterized by using Fourier transform infrared spectroscopy (FTIR), infrared microscopy, scanning infrared polariscope (SIRP), X-ray topography, etc. We have realized reduction of carbon, residual strain and extended defects, which may contribute the increase of solar cell efficiency.

Combustion Synthesis of Nanomaterials

An experimental study has been conducted in premixed and counterflow diffusion flames in order to obtain the nanocarbon materials. The original results in the field of synthesis of fullerenes, carbon nanotubes, syperhydrophobic soot,grapheme and nickel oxide nanoparticles in hydrocarbon flames were carried out for the last years at the Institute of Combustion Problems. Nanoparticles of nickel oxides contribute to the efficient absorption of light energy. Surfacing on the surface of a silicon solar cell of led to an increase in solar cell efficiency by 3%.

The effect of light soaking on crystalline silicon surface passivation by atomic layer deposited Al2O3

The effect of light soaking of crystalline silicon wafer lifetime samples surface passivated by thermal atomic layer deposited (ALD) Al2O3 is investigated in this paper. Contrary to other passivation materials used in solar cell applications (i.e., SiO2, SiNx), using thermal ALD Al2O3, an increase in effective carrier lifetime after light soaking under standard testing conditions is observed for both p-type (∼45%) and n-type (∼60%) FZ c-Si lifetime samples. After light soaking and storing the samples in a dark and dry environment, the effective lifetime decreases again and practically returns to the value before light soaking. The rate of lifetime decrease after light soaking is significantly slower than the rate of lifetime increase by light soaking. To investigate the underlying mechanism, corona charge experiments are carried out on p-type c-Si samples before and after light soaking. The results indicate that the negative fixed charge density Qf present in the Al2O3 films increases due to the light soaking, which results in an improved field-effect passivation. Numerical calculations also confirm that the improved field-effect passivation is the main contributor for the increased effective lifetime after light soaking. To further understand the light soaking phenomenon, a kinetic model—a charge trapping/de-trapping model—is proposed to explain the time dependent behavior of the lifetime increase/decrease observed under/after light soaking. The trap model fits the experimental results very well. The observed light enhanced passivation for ALD Al2O3 passivated c-Si is of technological relevance, because solar cell devices operate under illumination, thus an increase in solar cell efficiency due to light soaking can be expected.

Laser induced quasi-periodical microstructures with external field modulation for efficiency gain in photovoltaics

The overall reflectivity of silicon is decreased by 10% altering the surface topology by ultra-short pulsed laser ablation and resulting in an efficiency increase of solar cells. The size of quasi-periodical μm-structures on the surface can be defined by the applied laser parameters. The topology is additionally adapted in size and distance of the microstructures at constant laser parameters with a specifically applied external electrical field leading to a cone-like microstructure with an adjustable light-trapping geometry. On large scale multicrystalline silicon solar wafers with a laser generated μm-scale surface topology were processed into cells with an absolute efficiency gain.

Efficiency Improvement in P3HT:CdSe Quantum Dots Hybrid Solar Cells by Utilizing Novel Processing of a Dual Ligand Exchangers

ABSTRACTCdSe quantum dots of hexagonal Wurtzite crystal structure with an average diameter of ∼7 nm were synthesized and processed for bulk heterojunction solar cell applications. The UV-Vis absorption spectrum shows an excitonic peak at 625 nm and at 635 nm in synthesized and dual ligand exchanged samples, respectively. The synthesized quantum dots were successively ligand exchanged by pyridine and 2-propanethiol to remove the TOPO ligands on quantum dot surface and then hybrid solar cell devices were fabricated. Initially the weight ratio was optimized by using pyridine capped CdSe blend with P3HT polymer as an active layer in chloroform as a solvent on the patterned ITO glass. Then dual ligand exchanged CdSe was compared with pyridine optimized samples. The maximum solar cell conversion efficiency of 1.21% was achieved with Jsc of 4.1 mA/cm-2, VOC of 0.51 and FF of 44 compared to the optimized pyridine capped CdSe quantum dots where efficiency of 0.74% with Jsc of 2.15 mA/cm-2, VOC of 0.53 was observed. The increase in solar cell efficiency was attributed to the better ligand exchanged and additional treatment with 2-propanethiol at ambient temperature. Such an exchange of organic ligands by successive ligand exchanger will open new domain for hybrid solar cell research. The morphology of QDs and microstructures of the heterojunction active layer (P3HT:CdSe) were examined by using TEM, XRD, UV-Vis spectra, and IV curve techniques.