Current Density Voltage Research Articles

Development of Numerical Analysis Method for Cathode Sheath Considering Electron Emission From Cathode in Vacuum Arc

ABSTRACTIt is imperative to develop the simulation of vacuum arcs as a tool to aid electrode design in vacuum circuit breakers. Although the development of electromagnetic thermo‐fluid simulations for vacuum arcs has been reported, most of them do not take cathode sheath phenomena into account and have not been able to reproduce vacuum arc phenomena, especially cathode spots. As the first step, the cathode sheath voltage, cathode surface electric field, and temperature and field (T‐F) electron emission current were analyzed numerically on the basis of the space charge in the cathode sheath. In this study, the cathode sheath was assumed to exist when the charge density induced on the cathode surface is positive, and the temperature and density of vacuum arc plasma and cathode temperature, which are physical quantities obtained by electromagnetic thermo‐fluid simulation, were used as parameters of the analysis. As a result, the cathode sheath voltage, electric field, and electron emission current density can be calculated from the vacuum arc plasma temperature, density, and cathode temperature. Numerical results show that the electron emission current density has a dominant effect on the presence or absence of the cathode sheath.

Tandem dye-sensitized solar cells achieve 12.89% efficiency using novel organic sensitizers

This study presents a significant advancement in tandem dye-sensitized solar cells (T-DSSCs) through the strategic synthesis of novel triazatruxene (TAT) sensitizers MS-1 and MS-2. These organic sensitizers demonstrate exceptional light-harvesting capacity and overall performance, pushing the boundaries of power conversion efficiency (PCE) in DSSCs. The MS-1-based DSSCs achieved an impressive PCE of 12.81%, while MS-2 sensitizers reached a notable 10.92%. These efficiencies represent significant improvements over the conventional N719 dye (7.60%), demonstrating the potential of metal-free organic sensitizers in DSSC technology. The key to these noteworthy results lies in the molecular design of the organic sensitizers. The triazatruxene donor segment in the MS-1 and MS-2 dyes, featuring a rigid structure and efficient intramolecular charge transfer (ICT), proved to be a game-changer for photovoltaic properties. Building on these results, we explored an innovative parallel tandem cell (PT-DSSC) configuration. By connecting separate cells containing N719 and MS-1 sensitizers, we achieved a record efficiency of 12.89% with enhanced short-circuit current density (JSC) and open-circuit voltage (VOC)compared to single-dye cells. This study highlights the potential of molecular engineering in organic sensitizers and device optimization to enhance DSSC performance, paving the way for further advancements in solar cell technology.

Optimization of Sr3NCl3-based perovskite solar cell performance through the comparison of different electron and hole transport layers

Strontium Nitride Trichloride (Sr3NCl3) is a promising absorber material for solar cells due to its unique structural, electrical, and optical properties. We conducted a thorough investigation to scrutinize the structural, optical, and electronic characteristics and the photovoltaic efficiency of double-heterojunction solar cells utilizing Sr3NCl3 absorbers. Various metals were evaluated for the front and rear contacts to determine the optimal metal-semiconductor interface, with the study determining that silver (Ag) is the most suitable option for the front contact and nickel (Ni) for the back contact. The PV performance of innovative Sr3NCl3 absorber-based cell structures was evaluated with two different Hole Transport Layers (HTLs), MASnBe3 and CBTS, alongside ZnO and WS2 serving as the transition metal dichalcogenide (TMD) Electron Transport Layers (ETLs). This investigation examined a range of factors, such as layer thickness, operational temperature, doping density, defect densities at both the interfaces and within the bulk, carrier generation and recombination rates, quantum efficiency (QE), series versus shunt resistance, absorption coefficient, and current density-voltage (J-V) characteristics, utilizing the SCAPS-1D simulator software. Fine-tuning of both two HTL and ETL revealed that the highest power conversion efficiency (PCE) of 27.34 % with JSC of 19.78 mA/cm2, fill factor (FF) of 88.84 %, and VOC of 1.56 V was achieved with MASnBe3 HTL and ZnO ETL, while the lowest PCE of 25.55 %, with JSC of 19.77 mA/cm2, FF of 89.07 %, and VOC of 1.45 V was obtained for CBTS HTL and WS2 ETL, respectively. These findings highlight the promising potential of Sr3NCl3 absorbers with ZnO as ETL and MASnBe3 as HTL for developing advanced perovskites heterostructure solar cells for enhanced performance in the future.

Performance of yellow and pink oyster mushroom dyes in dye sensitized solar cell

A solar photovoltaic (PV) cell, is an electrical device that uses the PV effect to convert light energy into electricity. The application of oyster mushroom dyes in dye sensitized solar cell (DSSC) is a novel strategy to substitute the costly chemical production process with easily extractable, environmentally acceptable dyes. Both dyes of yellow and pink oyster mushrooms were extracted using the same process but dried into powder form using two techniques, warm drying and freeze drying. The characterization was carried out utilizing current-voltage (I-V) characterization for electrical properties, Ultraviolet-Visible (UV-Vis) spectrophotometer for optical properties, Field Emission Scanning Electron Microscopy (FESEM), and Atomic Force Microscopy (AFM) for the structural properties. It was found that freeze-dried pink and yellow oyster mushroom had shown the good properties for DSSC application as it produced energy bandgap which lies within the range of efficient dye sensitizer; 1.7 eV and 2.2 eV, the most uniform distribution of pores and a nearly spherical form in FESEM analysis, and AFM result obtained with the highest root mean square (RMS) roughness value (26.922 and 34.033) with stereoscopic morphologies. The data proved that mushroom dyes can be incorporated in DSSC with the optimization of drying method in the extraction process, dilution of dye and the layer of deposition on the glass substrate. The current density-voltage (J–V) characteristics of fabricated DSSC was characterized using Newport Oriel Sol3A solar simulator under AM 1.5 Sun condition (100 mW/cm2, 25 oC). From the result obtained by solar simulator, the fabricated FTO/TiO2/Pleurotus djamor dye/Pt indicated the Voc of 0.499 V and Jsc of 0.397 mA/cm2.

Impact of source/drain lateral straggle on GIDL current of low SS NC-FinFET

ABSTRACT In this paper, the gate-induced drain leakage (GIDL) issue in negative capacitance (NC-FinFET) has been comprehensively addressed using Sentaurus 3-D TCAD simulations. Incorporation of ferroelectric (FE) materials in the gate stack of NC-FinFET increases with current by 12% compared to that of baseline FinFET. A steeper sub-threshold swing (SS) of 8 mV/dec is achieved at a FE-thickness of 5 nm at a lateral straggle; (σ) = 0 nm. GIDL behaviour with respect to the variation of source/drain σ and gate oxide thicknesses of NC-FinFET with and without the presence of the GateTunneling model is thoroughly investigated. Investigations demonstrate that in NC-FinFET, there are steeper energy band profiles near source/drain owing to coupling of fringing fields to the ferroelectric layer, which exhibits a larger and prior commencement of the longitudinal band to band tunnelling current compared to conventional FinFET. Moreover, the effect of variation of σ on various parameters viz. SS, capacitance and transconductance has also been investigated, which shows better results for lower σ values. At σ = 0 nm, drain-induced barrier lowering is −187.23 mV/V as compared to that of σ = 5 nm, which is −355.3 mV/V. Furthermore, we have also investigated drain current noise spectral density (SID) and gate voltage noise spectral density (SVG) with respect to fin width (WFIN) at the optimised σ value.

Current density–voltage characteristics of exciplex-type organic light-emitting diodes expressed by a simple analytic equation

Exciplex-type bilayer organic light-emitting diodes (OLEDs) with ohmic contacts exhibited current density–voltage (J–V) characteristics that closely matched a simplified analytical model proposed by Nikitenko and Bässler. The analytical model is based on the following key assumptions: (i) complete hole–electron recombination at the interface between a hole transport layer (HTL) and an electron transport layer (ETL), (ii) ohmic contacts at the interfaces between metal electrodes and carrier transport layers, and (iii) electric-field-independent carrier mobilities in both HTL and ETL. The excellent matching shows that the simplified analytical model is sufficient to describe the J–V characteristics of the OLEDs. We also demonstrated that if the carrier mobility of one carrier transport layer is known, that of the other transport layer can be estimated using the equation derived by the simplified analytical model. The simplified analytical model provides a useful method to estimate carrier mobilities within carrier transport layers themselves in OLEDs.

Formation of n-type polycrystalline silicon with controlled doping concentration by flash lamp annealing of catalytic CVD amorphous silicon films

We investigated the properties of polycrystalline silicon (poly-Si) films formed by the flash lamp annealing (FLA) of hydrogenated amorphous Si (a-Si:H) films. Phosphorus- (P-) doped a-Si:H films with a thickness of several micrometers deposited by catalytic chemical vapor deposition (Cat-CVD) on a silicon nitride- (SiN x -) coated textured glass substrate are crystallized by FLA. P doping was achieved by flowing phosphine (PH3) during Cat-CVD, and the P concentration was controlled within a range of 1016–1021 cm−3, which was measured by secondary ion mass spectrometry. We also fabricated simple back-contact Si heterojunction solar cells to estimate a potential of flash-lamp-crystallized poly-Si as an absorption layer. The current-density–voltage (J–V) characteristics of the cells measured under 1 Sun light irradiation show an open-circuit voltage (V OC) of >0.4 V.

Effect of different set of electrodes for degradation of distillery spent wash promoted by electrocoagulation

ABSTRACT One of the most polluting industries in the world is the distillery industry, which produces strong distillery wastewater that has an adverse impact on the environment since it contains high organic matter. Using various combinations of electrodes in the electrocoagulation process, to examined the operational variables, viz., total dissolved solids (TDS), electrical conductivity (EC) and turbidity from the distillery spent wash. With a constant pH of 7, an agitation speed of 500 RPM, and optimizing the operating parameters, viz., varying the electrode distance (2, 3, 4, 5, and 6 cm), voltage (5–25 volts) current density of 1.5 A/cm2, and electrolysis time (30–150 min). Aluminium (Al) electrodes were observed to perform slightly better than iron (Fe) and zinc (Zn) electrodes, with punched Al electrodes outperforming plane Al electrodes. The highest removal efficiencies were achieved with punched Al electrodes in an optimized condition of voltage 25 volts, electrode distance (2 cm), and electrolysis time 150 minutes, with removal efficiencies of 91% for TDS, 92% for EC and 92% for turbidity. This study highlights the potential of electrocoagulation with optimized parameters for improving the purification of distillery spent wash and enhancing the removal of TDS, EC, and turbidity.

Computational Optimization for CdS/CIGS/GaAs Layered Solar Cell Architecture

Multi-junction solar cells are vital in developing reliable, green, sustainable solar cells. Consequently, the computational optimization of solar cell architecture has the potential to profoundly expedite the process of discovering high-efficiency solar cells. Copper indium gallium selenide (CIGS)-based solar cells exhibit substantial performance compared to those utilizing cadmium sulfide (CdS). Likewise, CIGS-based devices are more efficient according to their device performance, environmentally benign nature, and thus, reduced cost. Therefore, the paper introduces an optimization process of three-layered n-CdS/p-CIGS/p-GaAs (NPP)) solar cell architecture based on thickness and carrier charge density. An in-depth investigation of the numerical analysis for homojunction PPN-junction with the ’GaAs’ layer structure along with n-ZnO front contact was simulated using the Solar Cells Capacitance Simulator (SCAPS-1D) software. Subsequently, various computational optimization techniques for evaluating the effect of the thickness and the carrier density on the performance of the PPN layer on solar cell architecture were examined. The electronic characteristics by adding the GaAs layer on the top of the conventional (PN) junction further led to optimized values of the power conversion efficiency (PCE), open-circuit voltage (VOC), fill factor (FF), and short-circuit current density (JSC) of the solar cell. Lastly, the paper concludes by highlighting the most promising results of our study, showcasing the impact of adding the GaAs layer. Hence, using the optimized values from the analysis, thickness of 5 (μm) and carrier density of 1×1020 (1/cm) resulted in the maximum PCE, VOC, FF, and JSC of 45.7%, 1.16 V, 89.52%, and 43.88 (mA/m2), respectively, for the proposed solar cell architecture. The outcomes of the study aim to pave the path for highly efficient, optimized, and robust multi-junction solar cells.

Optimizing sensitizer concentration from senna tora leaves for enhanced interfacial interactions in dye-sensitized solar cells

A novel approach is adopted for the determination of the optimum concentration of natural dye powder extracted from the leaves of Senna Tora in the solvent ethanol and soak the TiO2 coated FTO substrate to be used as photoanode of dye sensitized solar cell (DSSC). Various concentration (0.5 g/15 ml, 0.75 g/15 ml, 1 g/15 ml and 1.5 g/15 ml) of the dye powder in ethanol is subjected for UV–Visible, FTIR and PL Spectroscopic studies. Solar cells are fabricated with the sensitizer in Photoanode, I-/I3- electrolyte and counter electrode of graphite coated FTO are subjected for JV characterization to determine the best concentration of dye to give good photoconversion efficiency. From the study, it is found that, among the four concentrations of the dye in ethanol for the extraction of the dye, 1.5 g in 15 ml of ethanol has shown higher efficiency of 2.29 % with fill factor, short circuit current density and open circuit voltage of 0.84, 2.64 mA/cm2 and 1.03 V.

Nonplanar Nanographene: A Hydrocarbon Hole‐Transporting Material That Competes with Triarylamines

AbstractHole‐transporting materials (HTMs) are essential for optoelectronic devices, such as organic light‐emitting diodes (OLEDs), dye‐sensitized solar cells, and perovskite solar cells. Triarylamines have been employed as HTMs since they were introduced in 1987. However, heteroatoms or side chains embedded in the core skeleton of triarylamines can cause thermal and chemical stability problems. Herein, we report that hexabenzo[a,c,fg,j,l,op]tetracene (HBT), a small nonplanar nanographene, functions as a hydrocarbon HTM with hole transport properties that match those of triarylamine‐based HTMs. X‐ray structural analysis and theoretical calculations revealed effective multidirectional orbital interactions and transfer integrals for HBT. In‐depth experimental and theoretical analyses revealed that the nonplanarity‐inducing annulative π‐extension can achieve not only a stable amorphous state in bulk films, but also a higher increase in the highest occupied molecular orbital level than conventional linear or cyclic π‐extension. Furthermore, an in‐house manufactured HBT‐based OLED exhibited excellent performance, featuring superior curves for current density–voltage, external quantum efficiency–luminance, and lifetime compared to those of representative triarylamine‐based OLEDs. A notable improvement in device lifetime was observed for the HBT‐based OLED, highlighting the advantages of the hydrocarbon HTM. This study demonstrates the immense potential of small nonplanar nanographenes for optoelectronic device applications.

Nonplanar Nanographene: A Hydrocarbon Hole-Transporting Material That Competes with Triarylamines.

Hole-transporting materials (HTMs) are essential for optoelectronic devices, such as organic light-emitting diodes (OLEDs), dye-sensitized solar cells, and perovskite solar cells. Triarylamines have been employed as HTMs since they were introduced in 1987. However, heteroatoms or side chains embedded in the core skeleton of triarylamines can cause thermal and chemical stability problems. Herein, we report that hexabenzo[a,c,fg,j,l,op]tetracene (HBT), a small nonplanar nanographene, functions as a hydrocarbon HTM with hole transport properties that match those of triarylamine-based HTMs. X-ray structural analysis and theoretical calculations revealed effective multidirectional orbital interactions and transfer integrals for HBT. In-depth experimental and theoretical analyses revealed that the nonplanarity-inducing annulative π-extension can achieve not only a stable amorphous state in bulk films, but also a higher increase in the highest occupied molecular orbital level than conventional linear or cyclic π-extension. Furthermore, an in-house manufactured HBT-based OLED exhibited excellent performance, featuring superior curves for current density-voltage, external quantum efficiency-luminance, and lifetime compared to those of representative triarylamine-based OLEDs. A notable improvement in device lifetime was observed for the HBT-based OLED, highlighting the advantages of the hydrocarbon HTM. This study demonstrates the immense potential of small nonplanar nanographenes for optoelectronic device applications.

Enhanced photovoltaic efficiency in dye-sensitized solar cells with natural co-sensitizers from Annona squamosa, Malus domestica and Musa fruits

This study demonstrates the enhancement of photoelectric efficiency in dye-sensitized solar cells (DSSCs) using a co-sensitization technique with natural organic dyes. Pigments from Annona squamosa, Malus domestica, and Musa peels were used as co-sensitizers in various ratios to determine the optimal concentration for photon capture. Optical characterization was performed using absorption spectroscopy, while the photovoltaic properties were evaluated through power-voltage (P–V), current density-voltage (J-V), and electrochemical impedance spectroscopy (EIS) analyses. The co-sensitized DSSC with Annona squamosa and Malus domestica dyes achieved the highest power conversion efficiency (PCE) of 1.56 %, compared to 0.95 % and 0.10 % for the individual dyes. These findings underscore the significant efficiency gains achieved through co-sensitization with natural dyes.

The effect of fluorinated conjugated side chains on the photovoltaic performance of polymers based on benzodithiophene (BDT) and carbazolobistriazole (CTA)

Reasonable regulation of the structure-performance relationship is extremely crucial to enhancing the device performance of organic solar cells (OSCs). As a novel fused-benzotriazole (BTA) electron-accepting (A) unit, carbazolobistriazole (CTA) has excellent luminescent properties, and the alkyl chains on the three N atoms allow flexible modulation of polymer solubility. However, higher molecular energy levels and weak crystallinity restrict the enhancement of device performance. Herein, a new donor polymer PE97 with CTA as A unit and 4,8-bis(4-(2-ethylhexyl)-3,5-difluorophenyl)benzo[1,2-b:4,5-b’]dithiophene (BDT-P2F) as electron-donating (D) unit was designed and synthesized. In comparison with the first CTA-based polymer PE93 with 4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b’]dithiophene (BDT-TF) as D unit, PE97 realizes stronger molecular stacking conducive to modulation of the active layer morphology and a deeper highest occupied molecular orbital (HOMO) level, which are favorable to increase short-circuit current density (JSC) and open-circuit voltage (VOC) of OSCs. When paired with Y-series non-fullerene acceptor eC9-2F, PE97-based OSC devices have achieved a higher power conversion efficiency (PCE) of 15.5 %, with a VOC of 0.81 V, a JSC of 25.3 mA cm−2, and a fill factor (FF) of 75.7 %, which figures significantly surpass efficiency (13.6 %) of PE93-based devices. These results indicate that the BDT-P2F unit can excellently modulate the optoelectronic properties of CTA-based polymers. This highlights the potential of the BDT-P2F as a promising D unit for polymers with weak crystallinity and limited electron-withdrawing properties.

Airfoil cross flow field to enhance mass transfer capacity and performance for PEMFC

Proper design of the flow field in bipolar plates is important for improving proton exchange membrane fuel cells in water transport, gas distribution and net power density enhancement. Inspired by the fact that the streamlined design of an airplane airfoil makes the flow resistance reduced, a new airfoil cross flow field is proposed. Airfoil cross flow field is composed of a regular pattern of airfoil pins which are categorized in pin-type flow fields. The effects of different airfoil-pin shapes and arrangements on cell performance were explored. The results showed that airfoil cross flow field improved water management by finely modulating the airflow significantly increasing the gas flow rate in the channel. In addition, the airfoil cross flow field design achieves higher and more uniform oxygen distribution at the interface between the gas diffusion layer and the catalyst layer. The proper shape and arrangement of the airfoil-pins can effectively increase the net power density of the cell by 10.65 % and 2.49 % compared to the conventional parallel flow field and the square-pin flow field. Due to the streamlined design of the airfoil cross flow field, the voltage drop is approximately 60 % of that of the conventional parallel flow field and even slightly lower than that of the square-pin flow field, which demonstrates its high practicality. In summary, the airfoil cross flow field well coordinates the high current density and low voltage drop requirements of proton exchange membrane fuel cells, and some new points of view on flow field design are presented.

Characterization of Chlorophyll Based Dye-Sensitized Solar Cell using General-Purpose Photovoltaic Device Model

In dye-sensitized solar cells (DSSCs), light is absorbed by the sensitized dye. When light strikes the dye molecule, it absorbs photons and becomes excited to a higher energy state. This excited state allows the dye molecule to inject an electron into the conduction band of the semiconductor, generating an electric current. The selection of dye properties is very significant, as it can help to improve the performance of DSSCs. However, achieving an identical output current-voltage characteristic from the same batch of plants or fruits used as dyes is very difficult. Furthermore, improving the electrical performance, such as short-circuit current density and efficiency, of fabricated dye-sensitized solar cells is critical, as many experimental factors need to be considered. Therefore, to minimize the extra use of material resources due to the risk of unsuccessful fabrications and to obtain better performance ideally, conducting simulation-based studies is important to optimize the performance of DSSCs. The free software General-Purpose Photovoltaic Device Model (GPVDM) is a promising and interesting tool due to its free license and easy accessibility through a graphical interface for simulating optoelectronic devices, including OLEDs, OFETs, and various types of solar cells. This paper considers GPVDM, a 3-D photovoltaic device model, to simulate the proposed structure with different samples of chlorophyll dye for DSSC performance. The paper aims to characterize the high current density-voltage (J-V) of chlorophyll-based DSSCs and identify suitable photovoltaic simulation software for running simulations of chlorophyll-based DSSCs. Finally, the outcomes are compared with experimental data reported in various literature sources. The results show an enhanced short-circuit current density (Jsc) of 0.3556 mA cm-2 for Cordyline fruticose leaves (Chl E), which is the highest among the other dyes tested. The value of simulated short-circuit current density (Jsc) is slightly different from the experimented result Jsc reported in the published paper. In conclusion, GPVDM can be considered suitable for modeling DSSCs.

Zinc Oxide–Based Grätzel Cells Employing Anthocyanin Dye Sensitizers Emphasizing Environmental Sustainability

ABSTRACTThis research is centered on the investigation of a dye‐sensitized solar cell (DSSC) with a particular focus on the utilization of anthocyanin as a sensitizing agent, in conjunction with zinc oxide (ZnO) and lithium‐doped ZnO aggregates. A notable feature of this study is its emphasis on employing cost‐effective materials in the fabrication process, aligning with the quest for sustainable and economically viable solar cell technologies. This study explores a DSSC, specifically employing anthocyanin as a sensitizer, along with ZnO and lithium‐doped ZnO aggregates. The fabrication utilizes cost‐effective materials. The research delves into morphological studies of both ZnO and its doped counterpart. Fourier transform infrared spectra were recorded for both crude and purified dyes extracted from purple cabbage. The current density–voltage profile highlights superior power conversion efficiency in the DSSC using purified dye from purple cabbage sensitized with lithium‐doped ZnO semiconductor. Overall, these experimental findings underscore the potential of anthocyanin pigments for efficient energy conversion within the realm of renewable energy technologies. By employing low‐cost materials and thoroughly investigating the morphological and spectroscopic properties of the involved components, this research contributes to the ongoing efforts in advancing clean and sustainable solar cell technologies, thereby paving the achievement of environmental sustainability.

Space charge-induced capacitance recovery in blue quantum dot light-emitting diodes

In this work, we report the capacitance recovery behavior in the blue quantum dot light-emitting diode (QLED) by capacitance–voltage (C–V) characterizations. A comprehensive study of the C–V, dC/dV–V, and current density–voltage characteristics of pristine and shelf-aged devices suggests that capacitance recovery is associated with space charge-induced charge accumulation. At lower temperatures, the capacitance recovery in the shelf-aged device is efficiently suppressed due to the difficulty in building up the space charge, which supports our argument. Moreover, the capacitance recovery behavior of QLED only happens at low frequencies (a few hundred hertz), which is related to the time constant for charge accumulation at the selected voltage. Our work shows the effect of space charge on device capacitance and enriches the comprehension of carrier processes in QLED under AC measurement.

The n-MoO3/p-Si heterojunction photodiode: Influence of the MoO3 film thickness on the ultraviolet and infrared photodetector performance

Here, we studied the effect of the MoO3 thin film thickness on the ultraviolet (UV) and infrared (IR) photodiode properties of the n-MoO3/p-Si heterojunction structure. Initially, the metal molybdenum (Mo) thin films with different thicknesses (50,150, and 250 nm) were created via DC magnetron sputtering on a p-type Si substrate. Then, the MoO3 thin films were synthesized using a thermal oxidation method with an optimal oxygen flow rate of 60sccm. XRD and Raman analysis showed that the structure of prepared thin films has converted from an amorphous to an orthorhombic (α-MoO3) crystalline phase with increasing thickness. The optical transmittance of the layers was tuned by controlling the thickness, and the maximum transmittance for the 50 nm-thick film was achieved in the broad wavelength range of 300–1100 nm. The current density–voltage (J–V) characteristics indicate the prepared samples' rectifying behavior under dark conditions. The heterojunction photodiode with a 50 nm-thick MoO3 layer shows the best performance. This sample had a maximum amount of transmittance in the UV–visible and IR regions, compared to other samples, which leads to efficient electron-hole separation and transportation. This sample demonstrates a significant photoresponse ratio (ILight/IDark) of about 55 and 52.5 in the ultraviolet (UV) and infrared (IR) regions, respectively.

Enhanced photovoltaic efficiency in TiO2-based CdS quantum dot-sensitized solar cells by the introduction of ZnO:Al3+ nanoparticles

A technique to fabricate quantum dots-sensitized solar cells (QDSSCs) based on Titanium Oxide (TiO2) and Zinc Oxide (ZnO) nanoparticles (NPs) is reported. ZnO nanocubes of around 65 nm were synthesized by the sol–gel precipitation method. ZnO was doped with Al3+ to enhance the photovoltaic efficiency by promoting electron mobility to form an efficient photoelectrode added to TiO2. Current density–voltage (J-V) characterizations indicate that the addition of Al3+ doping in ZnO crystalline structure in the photoelectrode can significantly improve current densities and consequently the photoconversion efficiency (η) of the QDSSCs, achieving maximum η of 3.4 % with five ZnO nanocubes layers with a 0.0005 M Al3+ doping concentration. While with the undoped sample and bare TiO2, the obtained ήs were 2.85 and 1.93 %, respectively. The improved QDSSC photovoltaic performance was attributed to the increased light harvesting due to a large surface area by introducing Al-doped ZnO nanocubes into the available places of the TiO2 lattice. On the other hand, the increased electrical conductivity due to the Al3+ ion doped into the ZnO lattice at the divalent Zn2+ site allows electrons to move readily into the Al-doped ZnO conduction band. Additionally, according to electron lifetime studies, the Al-doped ZnO nanocubes act as a dielectric layer, enhancing the photogenerated charge extraction process due to the introduction of lattice defects, causing intermediate levels to obtain higher electron recombination resistance.