Efficiency Enhancement Of Solar Cells Research Articles

Significant Efficiency Enhancement in Ultrathin CZTS Solar Cells by Combining Al Plasmonic Nanostructures Array and Antireflective Coatings

In the few past years, the economic and eco-friendly Cu2ZnSnS4 (CZTS) solar cells have caught lots of attentions. However, due to rather poor efficiency, identifying deficiencies and making improvements is necessary. In the present study, the performance improvement of ultrathin CZTS solar cells was achieved through (1) incorporation of anti-reflective coating (ARC) on the surface of cell and (2) embedding Al plasmonic nanostructures with different radius, periods, and vertical positions in the absorber layer. Various thicknesses of CZTS absorber layer were simulated optically and electrically using FDTD and DEVICE solver of Lumerical software. The reference solar cell consists of a 1.5-nm-thick CZTS absorber and exhibit an efficiency of up to 5.67%, short-circuit current density (Jsc) of 18.48 mA cm−2 and open circuit voltage of 0.58 V. Result showed a remarkable performance enhancement of the solar cell in spite of a very thin absorber layer. For a 500-μm-thick CZTS solar cell with the assistance of ARC and embedding Al plasmonic nanostructures, the efficiency is increased to 7.45% due to an increase in Jsc to 22.62 mA cm−2 with an open circuit voltage of 0.62 V.

Efficiency enhancement of p-type multi-crystalline solar cells in different efficiency grades by hydrogenation with electron injection

P-type multi-crystal (mc-Si) solar cells are facing relative weaker competitiveness compared to mono-crystal silicon solar cells due to the efficiency improvement bottleneck. To further enhance the efficiency of p-type mc-Si solar cells, we have systematically investigated the technology of hydrogenation with electron injection (HEI) on p-type mc-Si solar cells with different power conversion efficiency (PCE) grades. Experimental results manifested that the efficiency promotion of cells with higher efficiency (HE) was lower compared to that of lower efficiency (LE) cells under the same HEI processing condition, whether for conventional or passivated emitter and rear cells. Further investigations were carried out to prove that the effectiveness of HEI treatment was closely related to the concentration of both available hydrogen and defect in the bulk of solar cells. This highlighted that the lower concentration of available hydrogen was more helpful for HE cells to improve the electrical performances, which was contrary to LE cells due to the different distribution of defects in the bulk. Besides, programing analysis was implemented to optimize the HEI treatment scheme of HE cells, and the PCE was finally improved by 0.63%rel. ± 0.05%. This result provided an improved technological process to further improve the efficiency gains in the production process, where a classification method was introduced according to the efficiency distribution before HEI treatment. The proposed method can distribute solar cells into appropriate grades to avoid wasting resources in mass production.

Enhancement of dye-sensitized solar cell efficiency through co-sensitization of thiophene-based organic compounds and metal-based N-719

Synthesis of five novel thiophene-based metal-free organic dyes, named IS1-5, to study their photophysical, electrochemical properties and photovoltaic performance as sensitizers and co-sensitizers for DSSCs. Dyes IS-5 are cyanoacetanilide derivatives, which are distinguishedby theirsmall size, the simple preparation method, and the presence of multiple anchoring species (CO and CN) within their molecular structure. From their UV/Vis. spectra, IS-4 and IS-5 displayed the highest molar extinction coefficient with a bathochromic-shift to the intramolecular charge transfer band. In addition, to recognize the potential of HOMO level and the potential of LUMO level among all IS1-5 dyes, the cyclic voltammetry technique must be used. Their characteristics assert that all dyes possess the qualifications essential to be used as a sensitizer for dye-sensitized solar cells (DSSCs). Interestingly, over co-sensitization, all dyes showed better photovoltage values (VOC) than the standard dye N-719. Among Dyes IS1-5, co-sensitizer IS-5 showed the highest photoconversion efficiency (η) of (8.09%) compared to the standard dye N-719 (7.61%). Moreover, electrochemical impedance spectroscopy (EIS) asserts the impact of this dye on improving charge transfer in TiO2. Finally, density functional theory (DFT) has been studied for dyes IS1-5 using Guassian09 software and the outcomes comfortably agree with experimental results.

Linking bridge improvement of ZnO/N719 interfaces via ammonia treatment for efficiency enhancement of dye-sensitized solar cell

Modifying the photoelectrodes is an interesting strategy for improving the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). In this study, ZnO films were surface-treated using an NH3 chemical vapor process. After appropriate treatment of the ZnO films, the PCE of the DSSCs was maximized at 2.77%, and the short-circuit current density (Jsc) and open-circuit voltage (Voc) were increased accordingly. These parameters were directly proportional to the dye-adsorption performance, which was enhanced by linking-bridge formation of a ZnO−N=dye complex. The complexes improved the ZnO/N719 dye interfaces and completed the dye adsorption; consequently, the Jsc of the DSSC improved from 7.55 to 8.28 mA/cm2 and the Voc improved from 0.57 to 0.61 V. The linking bridge also facilitated electron transport and reduced the recombination. These effects synergistically enhanced the PCE of the DSSC. Moreover, the NH3 vapor treatment did not significantly affect the morphology, shape, or crystalline structure of the ZnO film. Such a non-destructive post-treatment using the chemical vapor process can potentially realize low-cost, high-performance films for DSSCs and other advanced technologies.

Efficiency enhancement of Si nanostructure hybrid solar cells by optimizing non-radiative energy transfer from Si quantum dots

Non-radiative energy transfer (NRET) from silicon quantum dots (SiQDs) terminated with ligands is an effective way to improve solar cell efficiency. The NRET effect can be enhanced by minimizing the distance between SiQDs and the solar cell surface. SiQDs were inserted between poly (3,4-ethylene dioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) and Si nanostructures of hybrid heterojunction solar cells. To clarify dependence on ligand length, three different ligands of different lengths were investigated. 1-octene, which has the shortest ligand length, showed the greatest enhancement of NRET, resulting in the highest solar cell efficiency. The non-radiative energy transfer (NRET) effect in Si quantum dots (SiQDs) can be enhanced by shortening the ligand length, resulting in enhanced short circuit current, thus significantly improving the energy conversion efficiency of solar cells. • High-efficiency hybrid solar cells were fabricated by inserting SiQDs into hybrid solar cell with Si nanotips and PEDOT:PSS. • Non-radiative energy transfer from SiQDs terminated with ligands effectively enhanced conversion efficiency of solar cells. • SiQDs with shorter ligands had a higher conversion efficiency. • The highest conversion efficiency of 12.4% was given by hybrid solar cells with 1-octene terminated SiQDs.

Sm3+/Yb3+ co-doped GeO2-PbO glass for efficiency enhancement of silicon solar cells

Abstract Luminescent properties and energy transfer processes in GeO2-PbO glasses co-doped with Sm3+/Yb3+ were investigated. The concentration of Sm3+ was 1 mol% while the concentration of Yb3+ was 0.2 and 0.5 mol%. Judd–Ofelt intensity parameters Ω λ ( λ = 2,4,6 ) were calculated from absorption spectra of the co-doped glass samples, together with transitions probabilities A j j ′ and radiative lifetimes τ R . Visible and NIR emission spectra were obtained under excitation of wavelengths corresponding to the 6H5/2 →(6P7/2,6P3/2,4I11/2) transitions of Sm3+ resulting in different emission channels from 4G5/2 level energy to lower energy levels. The set of co-doped and undoped glasses were placed on the top of a conventional silicon solar cell and the relative efficiency was studied. Cooperative energy transfer between the Sm3+ ion and Yb3+ ion would probably be responsible for observed enhancement in the energy efficiency of about 10%.

Dual Defect-Passivation Using Phthalocyanine for Enhanced Efficiency and Stability of Perovskite Solar Cells.

Semiconducting molecules have been employed to passivate traps extant in the perovskite film for enhancement of perovskite solar cells (PSCs) efficiency and stability. A molecular design strategy to passivate the defects both on the surface and interior of the CH3 NH3 PbI3 perovskite layer, using two phthalocyanine (Pc) molecules (NP-SC6 -ZnPc and NP-SC6 -TiOPc) is demonstrated. The presence of lone electron pairs on S, N, and O atoms of the Pc molecular structures provides the opportunity for Lewis acid-base interactions with under-coordinated Pb2+ sites, leading to efficient defect passivation of the perovskite layer. The tendency of both NP-SC6 -ZnPc and NP-SC6 -TiOPc to relax on the PbI2 terminated surface of the perovskite layer is also studied using density functional theory (DFT) calculations. The morphology of the perovskite layer is improved due to employing the Pc passivation strategy, resulting in high-quality thin films with a dense and compact structure and lower surface roughness. Using NP-SC6 -ZnPc and NP-SC6 -TiOPc as passivating agents, it is observed considerably enhanced power conversion efficiencies (PCEs), from 17.67% for the PSCs based on the pristine perovskite film to 19.39% for NP-SC6 -TiOPc passivated devices. Moreover, PSCs fabricated based on the Pc passivation method present a remarkable stability under conditions of high moisture and temperature levels.

Plasmonic periodic nanostructures for enhanced photovoltaic response in thin film GaAs solar cells

Nanostructures supporting surface plasmon resonance are crucial for efficiency enhancement in thin film solar cells. A plasmonic nanostructure over GaAs layer consisting of Al nanospheres on the front surface and Ag nanocylinders on the rear surface of the GaAs layer with SiO2 as the back contact is studied for the first time. Using the finite-difference time-domain method, it is found that the optimal nanostructure enhances the short circuit current density by 45.38% and 14.76% in comparison to bare and Si3N4-coated thin film GaAs solar cells, while the enhancement in efficiency (η) is 46.83% and 15.11%, respectively. The plasmonic scattering by nanostructure and propagation of waveguide modes at the metal/dielectric interface are mainly responsible for these enhancements.

Efficiency enhancement of CZTSSe solar cells via screening the absorber layer by examining of different possible defects

This study represents the investigation of earth-abundant and non-toxic CZTSSe absorber materials in kesterite solar cell by using the Finite Element Method (FEM) with (1) electrical, and (2) optical approaches. The simulated results have been validated with the experimental results to define guidelines for boosting the cell performance. For improving the cell efficiency, potential barrier variations in the front contact, and the effect of different lattice defects in the CZTSSe absorber layer have been examined. Controlling the defects and the secondary phases of absorber layer have significant influence on the cell performance improvement. Previous studies have demonstrated that, synthesis of CZTSSe:Na nanocrystals and controlling the S/(S + Se), Cu/(Zn + Sn), and Zn/Sn ratios (stoichiometry) have significant effects on the reduction of trap-assisted recombination (Shockley–Read–Hall recombination model). In this work, a screening-based approach has been employed to study the cell efficiency over a wide range of defect densities. Two categorized defect types including benign defects ({N}_{t}<{10}^{16} cm−3 , Nt defines trap density) and harmful defects {(N}_{t}>{10}^{16} cm−3) in the absorber bandgap in the CZTSSe solar cell, by analyzing their position changes with respect to the electron Fermi level (Efn) and the Valence Band Maximum positions have been identified. It is realized that, the harmful defects are the dominant reason for the low efficiency of the kesterite solar cells, therefore, reducing the number of harmful defects and also total defect densities lead to the power conversion efficiency record of 19.06%. This increment makes the CZTSSe solar cells as a promising candidate for industrial and commercial applications.

Efficiency enhancement in planar perovskite solar cells under low-light illumination and ambient lighting

Hybrid organic-inorganic perovskite solar cells (PSCs) have attracted significant interest owing to their high power conversion efficiency (PCE) and low cost. Moreover, PSCs demonstrate high performance under low light illumination without significant reduction in PCE. However, photovoltaic properties of PSCs under low light conditions are rarely reported. Here, the potential of planar PSCs for efficient performance under low illuminance conditions was investigated. Planar perovskite solar cells with FTO/c-TiO2/c-SnO2/CH3NH3PbI3/Spiro-MeOTAD/Au architecture were studied under variable illumination intensities in the range of 10 – 1000 W/m2. Significant enhancement in PCE up to 18.4% was observed for planar PSCs under low light conditions (<100 W/m2), as compared to the 16% PCE value obtained under AM1.5 illumination. This was attributed to the decreased charge accumulation at the ETL/perovskite interface and increased charge collection efficiency under low light illumination. PSCs performance was additionally studied under artificial LED lighting (5500K, 1000 lux) and the PCE values exceeding 24% were obtained. The results of this work verify excellent low-light performance of planar PSCs and provide the possibility for their application as power sources for various low-power wireless devices (sensors, detectors, Internet of Things devices, etc.).

Highly red luminescent Nb2O5:Eu3+ nanoparticles in silicate host for solid-state lighting and energy conversion

Abstract A high intrinsic quantum yield and color purity red-emitting nanostructured Eu3+-doped 1-xSiO2-xNb2O5 materials were prepared by a new sol-gel route at different Si:Nb molar ratio for solid-state lighting and energy conversion. It was evaluated how the composition and annealing temperature can affect the structure of the materials and their luminescence features. Eu3+ ions distribution into the different symmetry sites of nanoscaled orthorhombic or monoclinic Nb2O5 particles considerately influenced their emission profile and efficiency. A UV and blue to red downshifting were detected, and by using Judd-Ofelt theory, high quantum intrinsic quantum yield up to 65% is calculated for the Eu3+ doped Nb2O5 nanoparticles upon excitation at 463 nm. Additionally, the chromaticity diagram figured out a red color purity up to 90.1% is obtained, making them promising material for solid-state lighting. The particle size and doping control make them possible to explore the solid-state property of nanoscaled Nb2O5 particles as a host, with the advantage of their homogenous dispersion in a silicate network, opening the possibility of their use as planar waveguides for solar cell concentrators and energy conversion for enhancement of solar cell efficiency.

Pb[N(CN)2]2―A novel and effective additive provides visual verifications elucidating efficiency enhancement of CH3NH3PbI3 perovskite solar cells

The newly developed Pb[N(CN)2]2 additives have been demonstrated for enhancing efficiency from 14.7% to 17.4% and from 15.5% to 18.2% for conventional (FTO/TiO2 as the substrate) and inverted (FTO/NiOx as the substrate) MAPbI3 perovskite solar cells (PVSCs), respectively. Different from many effective additives of PVSCs, Pb[N(CN)2]2 provides the first visual evidences (colors changing) of additives participating in the solution adduct of MAPbI3 precursors. Further experimental results reveal that the Pb[N(CN)2]2 additives slowdown the formation process of the MAPbI3 crystallite thin film, of which the grain size reaches up to 900 nm with 0.2 M concentration of Pb[N(CN)2]2 additives in the MAPbI3 precursor solutions (1 M), accordant with the optimal concentration of Pb[N(CN)2]2 additives in enhancing efficiency of MAPbI3 PVSCs. We understand the role of Pb[N(CN)2]2 additives in MAPbI3 PVSCs through color photos (of precursor adduct solution and the adduct solid isolated from solutions), infra-red (of adduct solid isolated from solution), UV–visible absorption, photoluminescence, static and time-dependent powder X-ray spectroscopies.

Efficiency Enhancement of CZTS Solar Cells Using Al Plasmonic Nanoparticles: The Effect of Size and Period of Nanoparticles

In the present study, the performance improvement of the promising eco-friendly Cu2ZnSnS4 (CZTS) solar cells have been investigated numerically using Al plasmonic nanoparticles. The optical and electrical simulations were performed using the finite-difference time-domain (FDTD) method. It was revealed that loading plasmonic nanoparticles on the topmost layer of the CZTS solar cell leads to light absorption enhancement in the cell. By sweeping the radius of plasmonic nanoparticles from 20 nm to 60 nm, a significant enhancement in the efficiency occurred. The variation of the external quantum efficiency (EQE) and photovoltaic current density–voltage (J–V) curve under air mass of AM1.5 with and without plasmonic nanoparticles were also studied.

Effect of polyaniline (PANI) on efficiency enhancement of dye-sensitized solar cells fabricated with poly(ethylene oxide)-based gel polymer electrolytes

Ionically conducting gel polymer electrolytes can be used effectively to improve the problems associated with liquid electrolytes in dye-sensitized solar cells (DSSCs) and in particular to reduce their electrode degradation. In this work, gel polymer electrolytes containing poly(ethylene oxide) (PEO), LiI, and I2 were used as the redox electrolyte and conducting polymer; polyaniline (PANI) as an additive was introduced to the PEO-based electrolytes. The effect of incorporating PANI into the PEO-based gel electrolyte on iodide ion conductivity and solar cell performance was studied. The gel polymer electrolyte without PANI showed a conductivity of 1.23 × 10−3 S cm−1 at room temperature, while the electrolyte incorporating 1.5 wt% PANI showed an enhancement in conductivity increasing its value up to 1.87 × 10−3 S cm−1. While the DSSCs fabricated without PANI in the electrolyte showed 5.00% efficiency, the DSSCs fabricated with 1.5 wt% PANI-incorporated polymer electrolyte showed 6.56% efficiency under the same illumination of 100 mW cm−2(AM 1.5) simulated sunlight. Ionic conductivity and FTIR results suggest that the increase in electrolyte conductivity and the enhancement of DSSC performance appear to be due to the combined result of the plasticizing effect on decreasing the crystallinity of the PEO polymer and the improved ionic dissociation due to “trapping” and immobilizing the Li+ cations in the polymer matrix by PANI, creating more iodide (I−) ions in the redox medium.

Effect of modified double-sided grating structures on efficiency enhancement of thin-film silicon solar cells

Enhancement of optical to electrical conversion is vital for improving the efficiency of any solar cell. In recent years, use of thin films instead of bulk wafers has resulted in a huge reduction of production cost, and as such, efficiency enhancement of thin-film solar cells is considered in this study. Though this enhancement depends on several factors, most significant among them is the increase in light absorption within the active material of the solar cell. In this work, various types of grating structures on both sides of active solar cell material for light trapping are studied in detail, and a new type of arrangement of optimized grating structure that significantly improves the light absorption is selected. Enhancement of light absorption for change in dielectric material of the grating structure without changing the active material is also observed. Along with structural optimization, simulated electrical characterization of the samples was also performed, which yields a short-circuit current density of 29.27mA/cm2 with conversion efficiency of 14.51%, having a fill factor of 0.83 for a typical ultrathin layer of active material of thickness 2 µm. This is quite significant because typical cells of this category have much lesser conversion efficiency.

Efficiency enhancement of silicon solar cells by silicon quantum dots embedded in ZnO films as down-shifting coating

In the present work, the incorporation of silicon quantum dots (SiQDs) in zinc oxide (ZnO) films to develop coatings that improve the efficiency of silicon solar cells is reported. The down-shifting conversion of the SiQDs was used to enhance the efficiency of a photovoltaic device. The room temperature spectrum centered at 510 nm (2.43 eV) for the SiQDs is shown. The transmittance of the SiQDs-ZnO samples was measured and the band gap (Eg) was estimated through Tauc’s method. An increase on the band gap from 3.35 to 3.55 eV as function of the incorporation of SiQDs was obtained. The influence of the SiQDs in the oxide crystallinity of the wurtzite structure was studied through the X-ray diffraction. To determine the current increase under a standard test condition (STC) was achieved and an overall efficiency of 17.58% was obtained using a SiQDs-ZnO coating on silicon solar cells. The synergistic effect of SiQDs addition to ZnO films was demonstrated.

Low-bandgap mixed tin–lead iodide perovskites with reduced methylammonium for simultaneous enhancement of solar cell efficiency and stability

High-performance perovskite/perovskite tandem solar cells require high-efficiency and stable low-bandgap perovskite subcells. State-of-the-art low-bandgap mixed tin–lead iodide perovskite solar cells exhibit either a high power-conversion efficiency or improved stability, but not both. Here we report a two-step bilayer interdiffusion growth process to simultaneously meet both requirements for formamidinium-based low-bandgap mixed tin–lead iodide perovskite solar cells. The bilayer interdiffusion growth process allows for the formation of high-quality and large-grained perovskite films with only 10 mol% volatile methylammonium. Additionally, one-dimensional pyrrolidinium perovskite was applied to passivate the perovskite film and improve the junction quality, which resulted in a carrier lifetime of 1.1 μs and an open circuit voltage of 0.865 V for our perovskite film and device with a bandgap of 1.28 eV. Our strategies enabled a power-conversion efficiency of 20.4% for low-bandgap perovskite solar cells under AM 1.5G illumination. More importantly, an encapsulated device can retain 92% of its initial efficiency after 450 h of continuous 1 sun illumination. Low-bandgap tin–lead perovskites are key to all-perovskite tandem solar cells but simultaneous improvement in efficiency and stability has proven challenging. Now, Li et al. fabricate tin–lead perovskite cells with reduced methylammonium content that are 20.4% efficient and stable under illumination for 450 h.

Interface modification of SnO2 layer using p–n junction double layer for efficiency enhancement of perovskite solar cell

In this work, interface modification of SnO2 layer using p–n junction double layer is investigated for the efficiency enhancement of perovskite solar cell (PSC). For the double layer, a Sn additive layer was applied on a SnO2 layer by using the DC magnetron sputtering technique at various deposition times. The highest power conversion efficiency of 15.11% is obtained for PSC with a SnOx additive layer at 5 s sputtering time, compared to 12.89% for the best PSC without the additive layer. The effect of the SnOx additive layer on PSCs at optimum sputtering time is further explored via the photoconversion properties of both optical and electrical properties. From the results, it is found that the SnOx additive layer is essential for efficiency enhancement by forming the p-n junction with a SnO2 electron transporting layer (ETL) and modifying the interface between the ETL and the perovskite layer. The p-n junction of the ETL is observed via the diode-like behavior of I–V characteristics. The interface modification can enhance the PSC efficiency by improving the quality of the perovskite layer due to the larger grain size and higher absorbance, and by improving the charge transfer. The faster photogenerated charge transfer is confirmed by lower PL intensity and the shorter charge transfer lifetime is confirmed by the fitted open-circuit voltage decay. In addition, the SnOx additive layer can also eliminate the hysteresis effect of PSCs. This interface modification technique for PSC efficiency enhancement could be further explored for other ETLs.

Efficiency Enhancement of CIGS Solar Cells via Recombination Passivation

Cu(In,Ga)Se2 (CIGS) solar cells attract intense interest both in research and industry fields due to their high power conversion efficiencies, low costs, and high stabilities. The power conversion ...

Efficiency enhancement of perovskite solar cell by using doubly carrier transport layers with a distinct bandgap of MAPbI3 active layer

The comprehensive simulation study of perovskite solar cell (PSC) has been presented using doubly carrier transport layers and perovskite material with bandgap of 1.6–1.8 eV. The present study exhibits the maximum open-circuit voltage (Voc) nearly about 1.1 V, short circuit current density (Jsc) of 19.01 mA/cm2, fill factor (FF) of 0.89, and highest power conversion efficiency (PCE) about 18.52 %, respectively correspond to the active layer bandgap of 1.6 eV at AM1.5 illuminance. The thickness of the active layer is optimized for achieving an enhancement in the device efficiency. This leads to attain the maximum external quantum efficiency (EQE) with an average of 75 % for the PSC in the wavelength spanning from 380 nm to 780 nm. The result further indicates that the influence of the double carrier transport layer effectively modified in order to find better device performance and pathways for further device optimization.