Optical Transfer Matrix Method Research Articles

Effect of PEDOT:PSS optical properties at the frontal interface on electrical performance in MAPbI3 perovskite solar cells

This article presents a thorough analysis of perovskite-based solar cells (PSCs) by integrating optical and electrical simulations. The investigation includes simulations of both optical and electrical characteristics of a PSC configuration featuring a MAPbI3 active layer, PEDOT:PSS as the hole transport layer (HTL) at the front interface, and PC60BM and BCP at the back interface. Optical simulations utilized the optical admittance method and transfer matrix method, with optical constants such as refractive index (n) and extinction coefficient (k) derived from transmittance measurements of the fabricated layers. Electrical simulations were performed using the Solar Cell Capacitance Simulator One Dimension (SCAPS-1D) software, focusing on the influence of optical losses due to total reflection at the interfaces. Discrepancies in short-circuit current density (Jsc) of about 3 mA/cm2 were revealed between simulations employing optical constants of PEDOT:PSS determined via Tauc-Lorentz-Drude (TLD) and B-spline (BSPL) model fitting to transmittance data. Optimal parameters for achieving the highest power conversion efficiency (PCE) were identified, with PEDOT:PSS layer thicknesses below 15 nm and MAPbI3 layer thicknesses above 305 nm. The maximum efficiency ranged between 10.42 % and 12.10 %, close to conventional experimental perovskite solar cells with the same structure. A key observation highlighted the overestimation of Jsc and PCE when simulated total reflectance was neglected in electrical simulations. These findings underscore the significance of incorporating optical data into electrical simulations, offering critical insights for PSC optimization. Overall, this study enhances our understanding of the intricate relationship between optical and electrical parameters, essential for advancing high-performance PSC development.

Polarization properties in grating-gated AlN/GaN HEMTs at mid-infrared frequencies.

The plasmon resonances of grating-gated AlN/GaN HEMTs can occur in wide frequency regions at mid-infrared frequencies. However, the lack of polarization properties research in grating-gated AlN/GaN HEMTs prevents the application potential. In order to solve the problem, the polarization properties in grating-gated AlN/GaN HEMTs at mid-infrared frequencies were studied in the paper. After using the optical transfer matrix method to calculate the dispersion curves in grating-gated AlN/GaN HEMTs, the plasmon polaritons in conductive channel and phonon polaritons in GaN layer occur under TM incident waves rather than TE incident waves. The phenomenon illustrates the potential of polarization-selectivity has existed in grating-gated AlN/GaN HEMTs. To study the polarization properties of grating-gated AlN/GaN HEMTs in detail, the electric field distribution and transmission properties of the structure were simulated in COMSOL. The results show the excellent polarization-selectivity at mid-infrared frequencies in grating-gated AlN/GaN HEMTs. The studies of these characteristics indicate the vast potential for using grating-gated AlN/GaN HEMTs to design mid-infrared polarizers, mid-infrared polarization state modulators and other devices in the future.

Optimizing Device Structure of PTB7-Th:PNDI-T10 Bulk Heterojunction Polymer Solar Cells by Enhancing Optical Absorption

Using the optical transfer matrix method, we optimized the layered structure of a conventional and an inverted BHJ OSC with the active layer made of blended PTB7-Th:PNDI-T10 by maximizing the optical absorption and, hence, the JSC. The maximum JSC thus obtained from the optimised structure of the inverted OSC was 139 Am−2 and that of the conventional OSC was 135 Am−2. Simulation of the electric field distribution in both inverted and conventional OSCs showed that the formation of a single CIP was obtained in the active layer of thickness 105 nm in both OSCs. As the light incidents from the ITO side, it was found that excitons were generated more closely to ITO electrode, which favors the efficient charge transport and collection at the opposite electrodes in the inverted OSC, which produces higher JSC.

Research on Electromagnetic Wave Propagation and Optical Characteristics Based on Optical Transfer Matrix Method

The processing of electromagnetic waves by means of optical transmission matrix can be applied through multi-layer homogenization media, and finally real-time transmission can be realized. After that, it can derive the transmission matrix based on the interface and propagation matrix construction, and finally obtain the reflection and permeability coefficients. This article summarizes the content of the transmission matrix method based on previous work experience. The author discusses the propagation and optical characteristics of physical electromagnetic waves based on the optical transmission matrix method from four aspects: reflection-increasing film analysis, DBR design, reflectance calculation of fiber multi-directional laminates, plane wave propagation and reflection in the medium.

In-Depth Analysis of Organic Solar Cells Using Transport Equation and Optical Transfer Matrix Method with Detailed Analytical Derivations

Thin-film organic solar cell (OSC) performances have been investigated in detail by improved analytical computation in this work. The generation of excitons inside OSC has been estimated by using the optical transfer matrix method (OTMM) to include the optical phenomena of the incident light. The dissociation of these excitons into free charge carriers has been investigated to find the most appropriate one. OSC performances have been evaluated by an improved analytical solution of electrical transport equations including (i) exciton generation obtained from OTMM, (ii) dissociation probability incorporating Gaussian distribution to account for the natural fact of the difference in photon-energy producing excitons, (iii) recombination of charge carriers, all together. OSC properties such as JSC, VOC, FF, PCE, Pmax, absorbance, and quantum efficiency have been investigated with the variation of different parameters; this might be useful to improve OSC. Again, the presented detailed derivations of analytical expressions would be helpful for clear understanding.

Investigation of the Current of P3HT: PCBM-Based Organic Solar Cell Extracting the Spatial Recombination Coefficient of the Active Layer

The current of P3HT:PCBM-based organic solar cells was analytically investigated in this work. Position-and wavelength-dependent excitons generated by light were evaluated using the optical transfer matrix method. The charge carriers generated by dissociating excitons were estimated using an improved dissociation probability, incorporating a Gaussian distribution. A universal analytical equation was derived by solving the transport equation to calculate the current-producing holes and electrons. Similarly, another universal equation was derived to calculate the hole and electron currents. The total current, calculated using a constant recombination coefficient, is found to be different at different positions (position dependent), which is inconsistent because the total current should be position independent. The use of a constant recombination coefficient is the reason for this inconsistent result. The spatial recombination coefficients inside the active layer were extracted and used in the calculation, and the total current was found to be position independent; thus, the inconsistency was resolved. The current and its components have been investigated with respect to position, terminal voltage, solar irradiance, active layer thickness and wavelength. This work provides better results because it includes spatial recombination coefficients, space-and wavelength-dependent excitons, and improved dissociation probability in analytical calculations; therefore, it will help improve the prediction and design of organic solar cells.

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.

The prediction of carrier generation rate based on OTMM for perovskite solar cells based on different back electrodes

Abstract Perovskite Solar Cells (PSCs) have drawn tremendous attentions from scientific community due to their advantages of high efficiency and low-cost. However, the mechanism of photoelectron generation is unclear because the light field distribution is difficult to be quantitively characterized by conventional methods. The Optical Transfer Matrix Method (OTMM) has been applied in organic devices based on p-n structures. We have applied different materials as back electrode to examine the light propagation inside of planar p-i-n solar cells with regular structure (Glass/ITO/SnOx/CH3NH3PbI3/Spiro-OMeTAD/Back electrode). The simulations were performed by using OTMM to carry out the optical field modeling of simulated solar cells in visible-near infrared (NIR) range. Among the simulation models, it has been found that perovskite solar cells based on sliver electrode has highest light intensity oscillation and faster charge generation rate. But sliver electrode has lower stability because the iodine can diffuse to the interface and form AgI with the assist of NIR-induced thermal effect. By contrast, the independent graphene electrode has disadvantages of interlayer conductivity and transparency. Based on the simulation result, we recommend that the graphene can be applied as a buffer layer between perovskite and sliver electrode instead of being an independent electrode.

Comparative 1D optoelectrical simulation of the perovskite solar cell

The metal-halide perovskite solar cell has risen to the vanguard of photovoltaic research and offers the potential to merge low-cost fabrication with high-power conversion efficiency. Certainly, simulation along with experimental studies will contribute to a better understanding of the operation mechanism of PSC and the need to further improve device performance. In this study, the combinations of the optical transfer matrix method and electrical method based on the solar cell capacitance simulator (SCAPS) were used for 1D optoelectrical modeling of the planar PSC. In order to investigate the capability of this simple model, most of the related options such as absorption coefficient, optical reflection, defects, and interface trap were set. The comparison of the optoelectrical simulated EQE and JV curve of the CH3NH3PbI3 planar solar cell with the experimental ones showed that compared to the most only-electrical 1D modeling, the results are more similar to the experimental ones. However, this 1D model is not fully capable of much matching between the simulation and experimental results. By comparing the experimental and simulated results, the comparable VOC and JSC, as well as a difference in FF and PCE, are observed. In addition to the dark saturation current and ideality factor, the resistance losses and ionic emigration, which are not presented in this optoelectrical model, were introduced as the main factors for describing the differences in the values of the compared parameters.

Profiling exciton generation and recombination in conventional and inverted bulk heterojunction organic solar cells

Applying the optical transfer matrix method and the drift-diffusion equations, the efficient light absorption, exciton generation, and recombination rate in bulk heterojunction (BHJ) organic solar cells (OSCs) with conventional and inverted configurations are studied. Analysing the influence of the electric field component of the electromagnetic radiation propagating through the layered structure of BHJ OSCs and using contour plots of normalized modulus squared of the electric field, the constructive interference points (CIPs) which represent the positions of maximum absorption of photons and hence generation of excitons within the active layer are investigated for both the conventional and inverted OSCs. Also, the influence of the thicknesses of other layers in both the inverted and conventional structures is investigated. It is found that except the thickness of MoO3 in the inverted structure the thicknesses of other layers do not have any significant influence on CIPs. The maximum CIP occurs at an active layer thickness of 190 nm, regardless of the thickness of the second layer, which is MoO3, Ag, or ITO in the inverted structure and PEDOT:PSS, Al, or ITO in the conventional structure. The results of 3D plots of the normalized modulus squared of the electric field reveal that the absorption of photons at the end of the active layer in the inverted structure is higher than that in the conventional structure for all the effective wavelengths and different active layer thicknesses. It is expected that this study provides a deeper understanding of exciton generation within the two structures.

Reconstructing Space- and Energy-Dependent Exciton Generation in Solution-Processed Inverted Organic Solar Cells.

Photon absorption-induced exciton generation plays an important role in determining the photovoltaic properties of donor/acceptor organic solar cells with an inverted architecture. However, the reconstruction of light harvesting and thus exciton generation at different locations within organic inverted device are still not well resolved. Here, we investigate the film depth-dependent light absorption spectra in a small molecule donor/acceptor film. Including depth-dependent spectra into an optical transfer matrix method allows us to reconstruct both film depth- and energy-dependent exciton generation profiles, using which short-circuit current and external quantum efficiency of the inverted device are simulated and compared with the experimental measurements. The film depth-dependent spectroscopy, from which we are able to simultaneously reconstruct light harvesting profile, depth-dependent composition distribution, and vertical energy level variations, provides insights into photovoltaic process. In combination with appropriate material processing methods and device architecture, the method proposed in this work will help optimizing film depth-dependent optical/electronic properties for high-performance solar cells.

The Synthesis and Calculation of Heterostructural Photonic Crystals with Large Bandgap

Heterostructural photonic crystals (HPC) have attracted considerable interest due to its large photonic bandgap. Here we report a facile method to calculate and fabricate the heterostructural photonic crystals by using optical transfer-matrix method and polystyrene (PS) spheres with different particle sizes. Results suggest that the numerical simulation match well with the experimental spectra. In addition, compared with the single-structural photonic crystals (SPC), the HPCs have larger photonic bandgap, which is equal to a total of the photonic bandgaps of each SPC. Therefore, the HPCs with large bandgap can be well designed and then synthesized.

Analytical modeling of organic solar cells including monomolecular recombination and carrier generation calculated by optical transfer matrix method

An analytical model of organic solar cell has been developed including the effect of monomolecular recombination and charge carrier generation rate, simultaneously. The charge carrier generation rate, depending on position and wavelength, obtained from optical transfer matrix method, has been incorporated into electrical transport equation of carriers; this has led to combining optical and electrical phenomena into this model. Charge carrier generation rate profile has been investigated and included to develop the model. The proposed model addresses the propagation of light and the effects of optical phenomena like reflection and interference inside the device. Compared to previous models, this model is an improved version because of considering recombination mechanism and position and wavelength dependent generation rate simultaneously. This analytical model is useful for finding the performance of the organic solar cell device such as current-voltage relation, power-voltage relation, efficiency, etc. avoiding the complexities of numerical calculations. The proposed model has been validated by comparing the results obtained from the model with that of published experimental works. This model may help to analyse organic solar cells and optimize their parameters for improving the performance.

High acoustic strains in Si through ultrafast laser excitation of Ti thin-film transducers.

The role of thin-film metal transducers in ultrafast laser-generated longitudinal acoustic phonons in Si (100) monocrystal substrates is investigated. For this purpose degenerate femtosecond pump-probe transient reflectivity measurements are performed probing the Brillouin scattering of laser photons from phonons. The influence of the metallic electron-phonon coupling factor, acoustical impedance and film thickness is examined. An optical transfer matrix method for thin films is applied to extract the net acoustic strain relative strength for the various transducer cases, taking into account the experimental probing efficiency. In addition, a theoretical thermo-mechanical approach based on the combination of a revised two-temperature model and elasticity theory is applied and supports the experimental findings. The results show highly efficient generation of acoustic phonons in Si when Ti transducers are used. This demonstrates the crucial role of the transducer's high electron-phonon coupling constant and high compressive yield strength, as well as strong acoustical impedance matching with the semiconductor substrate.

基于光学传输矩阵的太赫兹时域光谱分析

We have presented the theoretical method of extracting the optical functions from terahertz(THz) time-domain spectroscopy,which is based on optical transfer matrix. Compared with the conventional method of extracting main pulse,this method can be generalized to the cases that the main pulse and the subpulses can not be distinguished. Meanwhile,we have obtained the complex refractive indices of sapphire from 0. 3 to 1. 0 THz by the method of optical transfer matrix. Compared with the results from the method of extracting main pulse,the security and accuracy of the optical transfer matrix method are both tested and verified. The theory present in this paper provides a solid theoretical foundation for analyzing the THz time-domain spectroscopy of the cases that the main pulse and the subpulses can not be distinguished.

Influence of substrate refractive index and antireflection coating on excitons generation in organic solar cell

The paper presents the results of theoretical analysis involving the influence of the refractive index of the substrate and the presence of the antireflective layer on the number of generated excitons in the structure of organic photocell with bulk heterostructure. The optical transfer matrix method \(2\times 2\) was applied in the theoretical analysis.

Infrared dielectric mirrors based on thin film multilayers of polystyrene and polyvinylpyrrolidone

Thin film polymer multilayers were prepared by spin coating alternating layers of polystyrene and polyvinylpyrroli- done. Samples with 10, 20, 30, 40, and 50 layers were prepared with individual layer thickness values in the range 223-508 nm. These samples were measured using a Fourier transform infrared spectrometer and were found to display narrow photonic band gaps (∼0.04 to 0.06m wide) in their spectral response over the wavelength range 1.6 − 2.6m. The position of the photonic band gaps was controlled by varying the thickness of the individual lay- ers within the multilayer structures. This was achieved by varying the spin speed used during the deposition of the polymer layers. The peak reflectance of the multilayers was controlled by vary- ing the number of layers within the multilayer samples giving values in the range 20-80% (corresponding to transmittances of 80-20%). Calculated transmittance spectra were also obtained using an optical transfer matrix method. These calculated spec- tra were shown to be in good agreement with the experimental data obtained. These experiments demonstrate a facile approach to the production of low cost dielectric mirrors that have tai- lored photonic properties over a range of wavelengths that are currently important for applications in fibre optic based telecom- munications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 732-739, 2011

Transmission spectra characteristics of 1D photonic crystals with complex dielectric constant

The characteristics of photonic forbidden bands, transmission gain and absorption of one-dimensional (1D) dual-periodical photonic crystals (PC) with a complex dielectric layer were studied by using the optical transfer matrix (TM) method. The results show that the photonic band gap (PBG) of this structure is enlarged and many transmission resonance peaks appear in PBG. Large transmission gain for transmission peaks is obtained if the imaginary part of dielectric constant is negative. With the increase of the absolute value of the imaginary part, the transmission gain increases firstly and the transmittance gain gets to an apex. The imaginary parts of dielectric constant corresponding to transmission gain apex are different according to wavelength. However, the transmission ratio of resonance peaks is less than 1 if the imaginary part of dielectric constant is positive. The properties might be used to design multi-narrow-channel band filters and optical amplification devices synchronously.

Thin film polymer photonics: Spin cast distributed Bragg reflectors and chirped polymer structures

Polymer based photonic structures were produced by spin coating up to 50 alternating layers of polystyrene (PS) and poly(vinylpyrrolidone) (PVP) from mutually exclusive (orthogonal) solvents. The resulting thin film multi-layer structures were studied using a simple optical reflectivity apparatus and were shown to have narrow (10-20nm wide) reflectance bands in the visible region. The position of the reflectance bands was controlled by varying the spin speed used during production of the multi-layers and peak reflectance values of 55% were obtained for samples containing 50 layers. The results were shown to be in agreement with modified optical transfer matrix method calculations which include the effects of diffuse polymer interfaces. This modelling approach revealed that the width of the polymer/polymer interfaces formed by spin coating was in the range 15-20nm. Data and calculations were also obtained for chirped polymer photonic structures. These results were also shown to be in good agreement. These experiments demonstrate that simple processing methods such as spin coating can be used to produce organic photonic structures with tailored optical properties.

Optical design of 1D-PC polarization filters with multi-channel

The one dimension photonic crystal (1D-PC) polarization filters with four channels and nine channels are presented based on different angular responses of the 1D-PC band gap. By using the optical transfer matrix method (TMM), the filtering characteristics are studied numerically, and the results show that both of the filters have the even signal channel spacing, for each channel the polarization separation degree is more than 0.96, the quality factor is about 104 magnitude, and the band width is almost even. So the 1D-PC polarization filter is a promising candidate for multi-channel polarization filters.