Optimal Active Layer Thickness Research Articles

Simulation of SnO2/Cs2AgInBr6/CuO heterojunction solar cell using AMPS-1D modeling

Using the one-dimensional computer code AMPS-1D MPS-1D (Analysis of Microelectronic and Photonic Structures), we simulated a lead-free double perovskite cell made of Cs2AgInBr6. This study examines the influence of the thickness and acceptor density of the active layer (Cs2AgInBr6) on key solar cell parameters, including short-circuit current density (JSC), efficiency (Eff), fill factor (FF), open-circuit voltage (VOC), current-voltage characteristics (J-V)). Our results suggest that an optimal active layer thickness of 500 nm yields good performance for the studied solar cell. Furthermore, the ideal acceptor density for enhancing output parameters is in the range of 10¹3-10¹⁵ cm⁻³. Post-optimization, our findings reveal a Voc of 0.969 V, a Jsc of 29.402 mA cm⁻², and an FF of 0.876, resulting in an efficiency of 24.959%. The results from AMPS-1D simulations for a Cs2AgInBr6 lead-free double perovskite solar cell suggest that this material and device structure can achieve high efficiency and good performance characteristics.

Suppressing leakage current by interfacial engineering for highly sensitive, broadband, self-powered FACsPbI3 perovskite photodetectors

Dark current is considered as one of the important parameters to suppress temporal noise and enhance sensitivity of photodetectors. This study shows the effect of active layer thickness and different interfacial layers in the suppression of leakage current. High-sensitivity (D* > 1012 Jones) perovskite photodetectors (PPDs) are fabricated using the device structure of ITO/PEDOT: PSS/FA0.95Cs0.05PbI3 (dPVSK)/ electron transport layer (ETL)/BCP/Ag with noise current <1 pA Hz−½. These PPDs have a broadband response from near-ultraviolet to near-infrared region (300–840 nm). The overall performance of the PPDs enhanced for the optimal thickness of active layer of dPVSK = 600 nm and ETL PC60BM layer thickness of dETL = 50 nm. The total noise current of the PPD is further suppressed by replacing the ETL PC60BM (in = 63.11 fA Hz−½) layer by a PC70BM (in = 33.41 fA Hz−½) layer. This further improved other figures of merit for these PPDs. Comparison with published reports on PPDs is included to compare with the state-of-the-art detectors.

A parametric analysis of concentration losses in an anode of a solid oxide fuel cell

The purpose of this paper is to discuss the loss of voltage in a Solid Oxide Fuel Cell (SOFC) as a result of the irreversible diffusive transport of gases through the microscopic pores of its fuel electrode. The voltage loss is estimated by solving the diffusive-convective equations, and current conduction equations in a computational domain based on data from Focused Ion Beam Scanning Electron Microscopy. The simulation includes both the binary diffusion and the free-molecular diffusion phenomena by employing Cylindrical Pore Interpolation Model. Butler-Volmer model is used to compute the reaction rate. Ion and electron current conduction is based on empirical relationships reported in the literature. The total losses are decomposed to identify the contribution of the mass transport irreversibilities. The parametric study results form a concave surface, showing non-linear relationship between electrode thickness, and diffusion-related voltage losses. The optimal active layer thickness is estimated.

Influence of Active Layer Thickness of Reversible Solid Oxide Cells on the Electrochemical Performance of Water Electrolysis

As energy storage becomes increasingly more important in contemporary and future energy solutions, the ability of a solid oxide cell (SOC) to work reversibly as an electrolyzer/fuel cell gives this technology great potential for use in large energy storage projects1,2. In theory, it is possible to use the state-of-the-art solid oxide cells in electrolysis operation to produce fuel (i.e. split water into oxygen and hydrogen) or generate electricity and heat using the so-called fuel cell regime. In addition, it is possible to produce syngas (H2 + CO)1,2 by co-electrolyzing water and CO2.While the performance and stability of the solid oxide fuel cell (SOFC) are in focus of most research regarding this technology, the technological possibilities of reversible solid oxide cells (RSOC) are far less studied. Although both technologies mostly share their device composition and main architecture, using the SOC in electrolysis mode creates new degradation mechanisms and technological problems3,4.In this work the authors focus on the electrolysis performance of the RSOC. The authors analyzed the influence of active layer thickness on SOC performance in electrolysis mode by using a commercial solid oxide cell (Ni-3YSZ|Ni-8YSZ|8YSZ|GDC|LSC). The study has been performed to establish the optimal active layer thickness and therefore to maximize the SOC performance in electrolysis mode.Electrochemical characterization of SOC button cells has been conducted using electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic methods at several operating conditions including different temperatures and different water vapor contents in the gas stream. The gas compositions have been exchanged to simulate working conditions at different locations in the RSOC stack during electrolysis work. The results of the electrochemical studies have been analyzed using equivalent circuit fitting method of Nyquist plots. Complex analysis of different porous architectures and chemical compositions at different operating conditions gave more information on how the structure of the SOC determines the electrochemical performance of the water electrolysis process.

A Simple Approach for Unraveling Optoelectronic Processes in Organic Solar Cells under Short‐Circuit Conditions

AbstractThe short‐circuit current (Jsc) of organic solar cells is defined by the interplay of exciton photogeneration in the active layer, geminate and non‐geminate recombination losses and free charge carrier extraction. The method proposed in this work allows the quantification of geminate recombination and the determination of the mobility‐lifetime product (µτ) as a single integrated parameter for charge transport and non‐geminate recombination. Furthermore, the extraction efficiency is quantified based on the obtained µτ product. Only readily available experimental methods (current‐voltage characteristics, external quantum efficiency measurements) are employed, which are coupled with an optical transfer matrix method simulation. The required optical properties of common organic photovoltaic (OPV) materials are provided in this work. The new approach is applied to three OPV systems in inverted or conventional device structures, and the results are juxtaposed against the µτ values obtained by an independent method based on the voltage–capacitance spectroscopy technique. Furthermore, it is demonstrated that the new method can accurately predict the optimal active layer thickness.

Investigation on optimal active layer thickness and pore size in dual-layer NH3-SCR monolith for low SO2 oxidation by numerical simulation

Nitrogen oxides (NOx) and sulfur dioxide (SO2) are common gaseous pollutants in the flue gas of stationary resources, such as thermal power plants. The undesired oxidation of SO2 on the catalytic monolith for Selective Catalytic Reduction (SCR) with ammonia will cause deposition of ammonium bisulfate, corrosion and extra pressure drop to downstream devices. A dual-layer model of catalytic monolith was established in this work to thoroughly investigate the effects of active layer thickness on SCR reaction and SO2 oxidation under various operating parameters. Besides, the influences of different sizes of nanopore in catalyst on both reactions are discussed. Thus, optimal parameters and suggestions were given for the design of SCR catalytic monolith with low SO2 oxidation.

Overcoming Space‐Charge Effect for Efficient Thick‐Film Non‐Fullerene Organic Solar Cells

AbstractOrganic solar cells (OSCs) containing non‐fullerene acceptors have realized high power conversion efficiency (PCE) up to 14%. However, most of these high‐performance non‐fullerene OSCs have been reported with optimal active layer thickness of about 100 nm, mainly due to the low electron mobility (≈10−4–10−5 cm2 V−1 s−1) of non‐fullerene acceptors, which are not suitable for roll‐to‐roll large‐scale processing. In this work, an efficient non‐fullerene OSC based on poly[(5,6‐difluoro‐2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐(3,3′″‐di(2‐octyldodecyl)‐2,2′;5′,2″;5″,2′″‐quaterthiophen‐5,5′′′‐diyl)] (PffBT4T‐2OD):EH‐IDTBR (consists of electron‐rich indaceno[1,2‐b:5,6‐b′]dithiophene as the central unit and an electron‐deficient 5,6‐benzo[c][1,2,5]thiadiazole unit flanked with rhodanine as the peripheral group) with thickness‐independent PCE (maintaining a PCE of 9.1% with an active layer thickness of 300 nm) is presented by optimizing device architectures to overcome the space‐charge effects. Optical modeling reveals that most of the incident light is absorbed near the transparent electrode side in thick‐film devices. The transport distance of electrons with lower mobility will therefore be shortened when using inverted device architecture, in which most of the excitons are generated close to the cathode side and therefore substantially reduces the accumulation of electrons in the device. As a result, an efficient thick‐film non‐fullerene OSC is realized. These results provide important guidelines for the development of more efficient thick‐film non‐fullerene OSCs.

Recent Advances in the Determination of Optimal Active Layer Thickness for Bulk Heterojunction Organic Solar Cells

Organic solar cells have gathered much research interest in recent years because of their advantages like low-cost, flexibility and light-weight. This paper presents a first of its kind, critical review of the theoretical and experimental studies performed to determine the outcome of changing active layer thickness on the working of a bulk heterojunction organic solar cell. The functional principles of an organic solar cell along with its typical parameters are briefly outlined. This paper discusses the features of the active layer and response of these features to changing active layer thickness which determines the device performance. Subsequently we describe the changes occurring in the parameters of the solar cell, followed by a detailed account of the optimal thickness ranges for different bulk heterojunction solar cells. A concise description of the donor and acceptor material properties is also presented. In the last section, simulations performed by changing active layer thickness for two different active layer material combinations have been presented, wherein we used poly(3-hexylthiophene): P3HT as the electron donor and phenyl-C61-butyric acid methyl ester: PCBM as the electron acceptor for one cell and the other cell has poly(9,9-dioctylindenofluorene-co-benzothiadiazole): PIF8BT and N′-bis(1-ethylpropyl)-3,4,9,10-perylene tetracarboxy diimide: PDI as donor and acceptor respectively. The paper concludes with a brief discussion of the applicability of annealing process to improve the optimal active layer thickness ranges of organic solar cells.

High-Performance Additive-/Post-Treatment-Free Nonfullerene Polymer Solar Cells via Tuning Molecular Weight of Conjugated Polymers.

In recent years, rapid advances are achieved in polymer solar cells (PSCs) using nonfullerene small molecular acceptors. However, no research disclosing the influence of molecular weight (Mn ) of conjugated polymer on the nonfullerene device performance is reported. In this work, a series of polymers with different Mn s are synthesized to systematically investigate the connection between Mn and performance of nonfullerene devices for the first time. It is found that the device performance improves substantially as the Mn increases from 12 to 38 kDa and a power conversion efficiency (PCE) as high as 10.5% is realized. It has to be noted this PCE is achieved without using any additives and post-treatments, which is among the top efficiencies of additive- and post-treatment-free PSCs. Most importantly, the variation trend of the optimal active layer thickness and morphology is significantly different from the device with fullerene as acceptor. The findings clarify the effect of Mn on the performance of nonfullerene PSCs, which would benefit further efficiency improvement of nonfullerene PSCs.

Achieving an Efficiency Exceeding 10% for Fullerene‐based Polymer Solar Cells Employing a Thick Active Layer via Tuning Molecular Weight

AbstractRecently, the influence of molecular weight (Mn) on the performance of polymer solar cells (PSCs) is widely investigated. However, the dependence of optimal thickness of active layer for PSCs on Mn is not reported yet, which is vital to the solution printing technology. In this work, the effect of Mn on the efficiency and especially optimal thickness of the active layer for PBTIBDTT‐S‐based PSCs is systematically studied. The device efficiency improves significantly as the Mn increases from 12 to 38 kDa, and a remarkable efficiency of 10.1% is achieved, which is among the top efficiencies of wide‐bandgap polymer:fullerene PSCs. Furthermore, the optimal thickness of the active layer is also greatly increased from 62 to 210 nm with increased Mn. Therefore, a device employing a thick (>200 nm) active layer with power conversion efficiency exceeding 10% is achieved by manipulating Mn. This exciting result is attributed to both the improved crystallinity, thus hole mobility, and preferable polymer orientation, thus morphology of active layer. These findings, for the first time, highlight the significant impact of Mn on the optimal thickness of active layer for PSCs and provide a facile way to further improve the performance of PSCs employing a thick active layer.

Improved charge carrier lifetime in planar perovskite solar cells by bromine doping.

The charge carrier lifetime is an important parameter in solar cells as it defines, together with the mobility, the diffusion length of the charge carriers, thus directly determining the optimal active layer thickness of a device. Herein, we report on charge carrier lifetime values in bromine doped planar methylammonium lead iodide (MAPbI3) solar cells determined by transient photovoltage. The corresponding charge carrier density has been derived from charge carrier extraction. We found increased lifetime values in solar cells incorporating bromine compared to pure MAPbI3 by a factor of ~2.75 at an illumination intensity corresponding to 1 sun. In the bromine containing solar cells we additionally observe an anomalously high value of extracted charge, which we deduce to originate from mobile ions.

Research on photoemission and spectra response of NEA Ga1−xAlxN photocathodes

To improve the quantum efficiency of negative electron affinity (NEA) Ga1−xAlxN photocathodes, the photoemission process and performance parameters of the cathodes are discussed. According to “three-step” model, the influence of electron escape probability, electron diffusion length, and thickness of active layer on the quantum efficiency is simulated. Results show that increasing of electron escape probability and electron diffusion length is helpful for the t-mode and r-mode Ga1−xAlxN photocathodes. There exists an optimal thickness of active layer for the t-mode photocathodes, which is different from the r-mode one. This work lays a foundation for the design and preparation of NEA Ga1−xAlxN photocathodes.

High efficiency PTB7-based inverted organic photovoltaics on nano-ridged and planar zinc oxide electron transport layers

Consistently high PCEs of ~8% were achieved for the PTB7-based inverted organic photovoltaics on a variety of nano-ridged and planar ZnO electron transport layers (ETLs) as long as the optimal active layer thickness was carefully controlled for each underlying ETL.

Solution processed thick film organic solar cells

In this Review article, significant advances in materials development and processing methods toward efficient solution processed bulk-heterojunction thick film organic solar cells as well as the factors that determine the optimal active layer thickness are summarized.

Lithium ion rechargeable battery, galvanostatics: Computer simulation and calculation of characteristics of the anode active layer of arbitrary thickness with low lithium diffusivity

The work of a lithium ion rechargeable battery operating under galvanostatic discharge conditions is simulated. Attention is focused on the complete mathematical description of processes in electrode active layers. The central problem in the theory of lithium ion batteries is the possibility of analyzing the following two processes that proceed simultaneously in space and time: depletion and enrichment of the active substance (intercalator) grains with lithium atoms and the ohmic-limitation-induced redistribution of the electrode potential in time throughout the active layer thickness. A new approach to the central problem is considered. It is based on comparing the characteristic times of two main processes occurring in electrodes. Here, the lithium atom diffusivity in intercalator grains plays the decisive role. Two regions of diffusivity values, i.e., high and low, can be singled out. Algorithms are developed for solving the complete system of equations for the most complicated case, namely, active layers of arbitrary thickness with low diffusivity of lithium atoms. The following electrode working parameters (for anode) are calculated: optimal active layer thickness, discharge time, anode specific capacitance, and final potential at the active layer/interelectrode space interface.

Role of balanced charge carrier transport in low band gap polymer:Fullerene bulk heterojunction solar cells

AbstractLowering of the optical band gap of conjugated polymers in bulk heterojunction solar cells not only leads to an increased absorption but also to an increase of the optimal active layer thickness due to interference effects at longer wavelengths. The increased carrier densities due to the enhanced absorption and thicker active layers make low band gap solar cells more sensitive to formation of space charges and recombination. By systematically red shifting the optical parameters of poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐p‐phenylenevinylene] and 6,6‐phenyl C61‐butyric acid methyl ester, we simulate the effect of a reduced band gap on the solar cell efficiencies. We show that especially the fill factor of low band gap cells is very sensitive to the balance of the charge transport. For a low band gap cell with an active layer thickness of 250 nm, the fill factor of 50% for balanced transport is reduced to less than 40% by an imbalance of only one order of magnitude. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

发射层厚度对透射式GaAs光电阴极表面光电压谱的影响

Equations for surface photovoltage spectroscopy were deducted,by solving the on-dimensional diffusion equation for equilibrium minority carriers of transmission-mode GaAs phtotocathode.Through measuring the surface photovoltage curves for GaAs photocathodes with the active layer thichness of 1.6 and 2.0μm,doping concentration of 1×1019 cm-3,experiments and fitting curves fit very well.By leading the formulas for integral sensitivity of surface photovoltage spectroscopy,the inflection of active layer thickness for integral sensitivity was analyzed under certain body parameters through emulations.It was found that GaAs photocathodes have a optimal active layer thickness and the back-interface recombination velocity inflects more on optimal thickness than electron diffusion length.Furthermore,GaAlAs window layer could help to well reduce the back-interface recombination velocity for active layer thickness.

THE APPROXIMATE EXPRESSIONS OF THE FOUR LAYER ASYMMETRIC WAVEGUIDE CHARACTERISTICS

In this paper, based on the normalized electronic field and the eigenvalue equation for the four layer asymmetric structure, the approximate expressions of the normalized effective index and the radiation confirement factor were introduced, and the approximate equations for the near field and far field asymmetric Gaussian Profile were deduced.Using the above-mentioned analysis, the dynamic characteristics of the four layer asymmetric waveguide was investigated. From this, the analytic expressions of the injected carrier concentration profile and the gain profile were obtained, and the modal gain, the threshold current density, the optimal active layer thickness, and the optimal threshold current density can be calculated.The calculated results of a series of relation were discussed. We study further the structure parameter effect on the device.

AN INVESTIGATION OF DYNAMIC CHARACTERISTIC FOR THE BURIED CRESCENT InGaAsP/InP LASER

In this paper, the dynamic characteristic of the buried crescent InGaAsP/Inp laser is analysed by the computer simulation method. The dependences of the threshold current and the single model cut-off condition on the structure parameters such as the active layer thickness (centre) d0, the channel width W, the cavity length L, the stripe width s, and the material resistance Rx are obtained.Based on the simulation analysis, the approximate expression between the structure parameters and the threshold current is provided. From this, the laser physical characteristic can be estimated simply and directly, and the model of injection carrier Gaussian profile is also propounded. Using this model, the current spreading and the gain profile were correctly calculated, and a series of analytical expressions about the maximum gain gmax, the threshold current density Jth, the mode gain Gth, the optimal active layer thickness d0,min and the optimal threshold current density Jth,min ate derived. According to the analysis mentioned above, the optimal design parameters for this type of laser are obtained as follows:d0= 0.15-0.2 μm, W = 2-4 μm, L = 200 μm and s= 10-15μm.