Quantum Efficiency Curves Research Articles

Accurate Determination of Camera Quantum Efficiency from a Single Image.

Knowledge of spectral sensitivity is important for high-precision comparison of images taken by different cameras and recognition of objects and interpretation of scenes for which color is an important cue. Direct estimation of quantum efficiency curves (QECs) is a complicated and tedious process requiring specialized equipment, and many camera manufacturers do not make spectral characteristics publicly available. This has led to the development of indirect techniques that are unreliable due to being highly sensitive to noise in the input data, and which often require the imposition of additional ad hoc conditions, some of which do not always hold. We demonstrate the reason for the lack of stability in the determination of QECs and propose an approach that guarantees the stability of QEC reconstruction, even in the presence of noise. A device for the realization of this approach is also proposed. The reported results were used as a basis for the granted US patent.

Enhancing overall performance of thermophotovoltaics via deep reinforcement learning-based optimization

Thermophotovoltaic (TPV) systems can be used to harvest thermal energy for thermoelectric conversion with much improved efficiency and power density compared with traditional photovoltaic systems. As the key component, selective emitters (SEs) can re-emit tailored thermal radiation for better matching with the absorption band of TPV cells. However, current designs of the SEs heavily rely on empirical design templates, particularly the metal-insulator-metal (MIM) structure, and lack of considering the overall performance of TPV systems and optimization efficiency. Here, we utilized a deep reinforcement learning (DRL) method to perform a comprehensive design of a 2D square-pattern metamaterial SE, with simultaneous optimization of material selections and structural parameters. In the DRL method, only the database of refractory materials with gradient refraction indexes needs to be prepared in advance, and the whole design roadmap will automatically output the SE with optimal Figure-of-Merit (FoM) efficiently. The optimal SE is composed of a novel material combination of TiO2, Si, and W substrate, with its thickness and structure precisely optimized. Its emissivity spectra match well with the external quantum efficiency curve of the GaSb cell. Consequently, the overall performance of TPV is significantly enhanced with an output power density of 5.78 W/cm2, an energy conversion efficiency of 38.26%, and a corresponding FoM of 2.21, surpassing most existing designs. The underlying physics of optimal SE is explained by the coupling effect of multiple resonance modes. This work advances the practical application potential of TPV systems and paves the way for addressing other multi-physics optimization problems and metamaterial designs.

Performance analysis of LaFeO3 perovskite solar cells: A theoretical and experimental study

Lanthanum ferrite (LaFeO3) is a potential candidate for Perovskite Solar Cell (PSC) application. The transition metal oxide has strong electron-electron correlation which results in an increase in quantum efficiency (QE) of PSC. In this investigation, we reported synthesis of LaFeO3 perovskite material, simulation of LaFeO3-based PSC followed by experimental validation. The sol-gel method was employed to prepare nanoparticles of LaFeO3 for PSC application. The prepared perovskite material is analyzed by XRD, SEM, EDS, UV–Vis and FTIR. The photovoltaic (PV) application of synthesized LaFeO3 material is studied by SCAPS-1D. The LaFeO3-based PSC is simulated with various ETLs such as TiO2, PCBM, IGZO, In2O3, C60, ZnO, SnO2, WS2 and HTLs of Cu2O, CuInSe2, Spiro-OMeTAD, P3HT, D-PBTTT-14, V2O5, CFTS, CBTS. The simulation outcomes of 64 distinct configurations deduced the eight-best performing PSCs. For these eight PSCs, impact of thickness of perovskite absorber layer, operating temperature, defect density, series and shunt resistance, work function of back contact, J-V characteristics and QE curve has been studied. We have achieved theoretical maximum efficiency of 13.03 % for the configuration of FTO/WS2/LaFeO3/CBTS/Au. The optimized structure has experimentally obtained maximum efficiency of 0.79 %. This shows that it is promising material for future PV application.

Formation of a potential barrier by a ZnSXSe1−X electron-blocking layer to improve the efficiency of CdSe0.3S0.7/CdSe quantum dot sensitized solar cells

We designed and fabricated multilayer quantum dots sensitized solar cells (QDSCs) with TiO2 NPs/CdSe0.3S0.7/CdSe/ZnSXSe1−X, X = S/S + Se = 0, 0.7, 0.8, 0.9, and 1 photoelectrodes to achieve optimum power conversion efficiency (PCE). In the corresponding structure, incoming light is absorbed by the CdSe0.3S0.7 and CdSe quantum dots (QDs), while the ZnSXSe1−X QDs act as an electron blocking layer or passivation layer, forming an energy barrier that restricts electron mobility from the light absorbers to the polysulfide electrolyte. The beneficial effect of the alloyed ZnSXSe1−X layer is the adjustability of its nanoparticle size/bandgap energy proportional to variations in the concentration of anionic precursors X, according to optical results. The PCE value of the reference cell with the TiO2 NPs/CdSe0.3S0.7/CdSe photoanode is 4.15 %. Following the coating of ZnSe, ZnS0.7Se0.3, ZnS0.8Se0.2, ZnS0.9Se0.1, and ZnS QDs via two successive ionic layer adsorption and reaction (SILAR) cycles (2Sc) on the CdSe0.3S0.7/CdSe co-sensitized photoelectrode increasing stability and improving the PCE value to 4.9 %, 5.40 %, 5.70, 5.25 %, and 5.05 %, respectively. Next, by modifying the thickness of the champion cell's passivation layer, the QDSCs with TiO2 NPs/CdSe0.3S0.7/CdSe/ZnS0.8Se0.2 (3Sc) photoelectrode exhibit maximum photovoltaic performance parameters of short circuit current density (JSC) = 26.25 mA/cm2, open circuit voltage (VOC) = 560 mV, fill factor (FF) = 0.42 % and PCE = 6.15 %. This improvement in performance is the result of decreased internal energy loss and recombination of charge carriers at the interface between the electrolyte and photoelectrode, which increases electron collection efficiency and electron injection efficiency in the visible region according to the external and internal quantum efficiency curves.

Analysis of optical and electrical properties in CZTSSe thin film solar cells through the 2d theoretical modeling

In this work, a 2D simulator (i.e., SILVACO ATLAS simulator) was used for modeling the Cu2ZnSn(S, Se)4 (CZTSSe) thin film solar cells. This simulation study mainly focused on the influence of the electrical and optical parameters that describe the electrical properties of each layer and the absorbed radiation in the heterostructure. These two parameters are analyzed and optimized to get as high of an efficiency as possible. It was characterized by means of the simulation that the effect of the electrical and optical parameters on the solar cell output parameters (VOC,JSC,FF,andη) was studied. The other parameters, such as temperature, bandgap, mobility, and thickness, were also varied in this simulative study for optimizing the device performance. The second record efficiency of 12.6 % was observed for the CZTSSe thin film solar cell (TFSC). This obtained result was compared with the results attained from the SCAPS-1D simulation as well as the second record efficiency for CZTSSe TFSC. Moreover, the Haze function was used to characterize the transmittance and diffuse reflectance in the rough interfaces between the layers of the solar cell. The Haze function utilized the input data like roughness and correction prefactors, which mainly impact the root-mean-square interface roughness (σrms) value by studying the External Quantum Efficiency curve variation. After analyzing these parameters, the efficiency was slightly improved to 13.02 %. Therefore, theoretical modeling could be beneficial to design highly efficient devices without utilizing experimental resources.

Improvement and structure optimization of transmission-mode GaAs photocathode performance

In order to improve the performance of transmitted GaAs photoelectric cathode, the quantum efficiency curve of Chinese transmitted GaAs photoelectric cathode is compared with that of the product of American ITT company, showing that the integration sensitivity of Chinese transmitted photoelectric cathode is 2130 μA/lm, and the American ITT company’s reaches 2330 μA/lm. Through the matrix method to solve the three membranes, the theoretical reflectivity is obtained. Based on the uniform doping transmission GaAs photocathode quantum efficiency formula, by replacing the fixed value <i>R</i> with variable value <inline-formula><tex-math id="M1">\begin{document}$ {R}_{{\mathrm{t}}{\mathrm{h}}{\mathrm{e}}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20231542_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20231542_M1.png"/></alternatives></inline-formula>, adding the short wave constraint factor, and modifying the quantum efficiency formula, a modified uniform doping transmission GaAs photocathode quantum efficiency formula is obtained. Using the revised quantum efficiency, optical performance and integral sensitivity theory model, through fitting the quantum efficiency curve of American ITT company product , introducing the ITT cathode component performance parameters, comparing the performance parameters of Chinese product, the results show that the Chinese photocathode in the window layer, the thickness of the emission layer, electron diffusion length and rear interface composite rate has a certain gap with ITT’s. In order to shorten the gap between the two and optimize the cathode structure parameters, the transmission GaAs photocathode optical structure software is designed to further analyze the influence of the electron diffusion length and the emission layer thickness on the quantum efficiency of the photocathode. The results show that with an electron diffusion length of 7 μm and emission layer thickness of 1.5 μm, the transmitted GaAs photocathode sensitivity can be more than 2800 μA/lm. However, the large electron diffusion length has high requirements for cathode materials and preparation level. The reasons responsible for the performance gap between Chinese product and other country’s are that in China the growth process of cathode materials is not jet matureand the cathode preparation equipment is out of date . In this paper, we study the relationship between GaAs photocathode optical performance and photoemission performance, and further optimize the structural design of cathode components, which has certain guiding significance for improving the cathode quantum efficiency and the level of image intensifier.

Optical properties and stability of Coumarin 7 luminescent down shifting layers in different host polymers

In this work, pristine Coumarin 7 (C7) layers and mixtures of C7 with Poly(methyl methacrylate) (PMMA), Polycarbonate (PC) and Polyurethane (PU) were produced by drop casting and characterized by UV-vis absorption and Photoluminescence spectroscopy, aiming at investigating the effect of the different host polymers on the optical properties of the luminescent material. The optical properties of the luminescent down shifting LDS layers are adjusted by using the different polymers, different solvents and by changing the relative concentration of the host, resulting in Photoluminescence Quantum Yield (PLQY) values of 98, 92 and 96% for C7:PMMA, C7:PC and C7:PU layers, respectively. The overall enhancement in emission is about 5 times when compared to pristine C7 layers (PLQY = 19% in DMSO solvent). The effect of the different LDS layers in a simulated Perovskite Solar Cell (PSC) was assessed using Rothemundś model. The External Quantum Efficiency (EQE) curve of the simulated device was obtained using SCAPS-1D software and calculations with Rothemund's model show enhancements of about 11, 15 and 17% in the short-circuit current density when C7:PC, C7:PU and C7:PMMA LDS layers are used, respectively. The stability of the layers under different stressing conditions was examined with Differential Scanning Calorimetry DSC measurements and optical characterizations. There is no dramatic effect of the temperature on the optical properties of the layers, however, upon interaction with light, PLQY values are significantly reduced during the first hours of light soaking. C7:PMMA layers were the more stable combination after the light-soaking stability tests, indicating that PMMA is the most suitable option as host matrix for organic LDS dyes, with potential applications in photovoltaic devices. Our work highlights the importance of choosing the host polymer and evaluate its stability for the successful application of organic LDS layers in solar cells.

How backreflection contributes to light absorption for high-performance radial junction photovoltaics

A robust radial junction (RJ) structure directly constructed upon the surface of a flexible Al foil substrate shows a promising potential to boost wearable and portable applications, where the silicon nanowire (SiNW) supported multilayer has proven beneficial in excellent mechanical stability and sufficient light harvesting. Assigned to the beneficial backreflection contributed by the Al foil, a much larger light current can be achieved than that on glass. While a comprehensive understanding of the light absorption under the backreflection of the substrate remains mainly unexplored. Herein, a straightforward comparison of light absorption of RJ units on Al and glass substrates, within a theoretical framework based on a finite-element simulation, is performed. Then, taking SiNW geometric parameters and i-layer thickness into account, the evolutions of light harvesting and the external quantum efficiency curves are systematically studied. These results indicate that, under the backreflection of the substrate, the light absorption shows a reduced dependency on SiNW geometry and i-layer thickness to some extent, laying a critical basis to establish a simpler/easier fabrication process for high-performance flexible RJ thin film photovoltaics.

A novel method of determining bias lights for spectral response measurement of GaAs multi-junction laser power converters and its applications

Quantitative electrical analysis of sub-cells is crucial for the designing of high-efficiency GaAs multi-junction laser power converters (MJLPCs). However, finding suitable bias lights to separate the electrical performance of sub-cells is an enormous challenge, due to GaAs MJLPCs being assembled by GaAs p-n junctions. Therefore, this study proposes a novel and general method of determining bias lights for the SR measurement of GaAs MJLPCs based on the variation rules of simulated short-circuit current densities with wavelengths in the sub-cells of GaAs MJLPCs. By the method of determining bias lights, the external quantum efficiency (EQE) curves of a GaAs four-junction LPC have been successfully measured for the first time, which confirms the validity of the method.

New optimized HIT solar cell using wide-bandgap nc-3C-SiC:H as a window layer

This study focuses on the investigation of HIT solar cell using nanocrystalline hydrogenated cubic silicon carbide (nc-3C-SiC:H) as a window layer. The selection of nc-3C-SiC:H is motivated by its wide bandgap, high electron drift velocity, and exceptional optical, electrical, and structural properties. Employing SCAPS-1D simulator, a comprehensive simulation analysis of thin nc-3C-SiC:H-based solar cell was conducted. By analyzing the current–voltage and quantum efficiency curves, the impact of doping concentration in the window layer was examined, covering a range from [Formula: see text] to [Formula: see text]. A rapid degradation of [Formula: see text] was observed for high doping concentrations. Additionally, the temperature dependence of external DC parameters for the temperatures 273, 300, and 318[Formula: see text]K was explored under AM1.5G and AM1.5D sunlight spectra. The application of two distinct light spectra resulted in the DC parameters exhibiting minimal variation or similarity. The study also took into account the influence of window thickness variation, temperature, and doping concentration. The findings demonstrate a remarkable influence of temperature and doping concentration on the DC parameters. [Formula: see text] value of 30.29[Formula: see text]mA/cm2 was achieved with a 3-nm thickness and an optimal efficiency of 19.48% was registered with a doping concentration of up to [Formula: see text], showcasing the promising potential of nc-3C-SiC:H.

A new Na2BaCa(PO4)2: Eu3+ red-emitting phosphor with excellent thermal stability and high quantum efficiency for WLEDs

A series of new red phosphors Na2BaCa(PO4)2: xEu3+ was synthesized by the high temperature solid phase reaction method. Through employing X-ray diffraction, scanning electron microscope, photoluminescence spectroscopy, quantum efficiency curves and high-precision rapid spectrometers, a systematic investigation was conducted on the microstructure and optical characteristics of the material. The XRD analysis of Na2BaCa(PO4)2: xEu3+ shows the sample to be a pure phase. The spectroscopic results show the presence of a red emission peak originated from 5D0 → 7F2 transition, and the quenching mechanism is attributed to interaction between nearest neighboring ions. Under 423 K, the fluorescence intensity of Na2BaCa(PO4)2: 0.2Eu3+ phosphor can still maintain 94.82 % of the value observed at 298 K, and the thermal activation energy ΔE reaches up to 0.3543 eV. The CCT of the LED packaged with Na2BaCa(PO4)2: 0.2Eu3+ was measured to be 4314 K, with the CIE coordinates (0.3658, 0.3600), which is very close to the point of standard white light source. The quantum efficiency of Na2BaCa(PO4)2: 0.2Eu3+ was measured to be 82.92 %. All results indicate that Na2BaCa(PO4)2: 0.2Eu3+ is suitable for WLED applications.

A novel red-emitting K5La(MoO4)4:Eu3+ phosphor with a high quantum efficiency for w-LEDs and visualization of latent fingerprints

A new series of red luminescent K5La(MoO4)4:xEu3+ (KLMO:xEu3+) phosphors (x = 0.05–1.00 mol) was successfully synthesized by a high-temperature solid phase reaction at a low reaction temperature (600 ℃). The X-ray diffraction (XRD) pattern, photoluminescence properties, thermal quenching mechanism, quantum efficiency, and lifetime decay curves of the phosphors were measured and discussed in detail. The prepared phosphors exhibited strong red-light emission (at 615 nm) upon excitation at 394 nm, attributed to the electric dipole 5D0-7F2 transition of Eu3+. The optimal doping concentration of phosphors is 0.8 mol. The quenching temperature of the KLMO:0.80Eu3+ phosphor was found to exceed 480 K, with high activation energy (Ea) of 0.43 eV, showing good thermal stability. Impressively, the KLMO:0.80Eu3+ phosphor with a 0.8 mol concentration of Eu3+ doping also has an internal quantum efficiency (IQE) of up to 84.5%. The packaged white light emitting diode (w-LED) showed a good color rendering index (CRI) (89), correlated color temperature (CCT) (5117 K), and the Commission International de L′Eclairage (CIE) chromaticity coordinates (0.342, 0.345). Furthermore, the KLMO:0.80Eu3+ phosphor was surface-functionalized with oleic acid (OA) (KLMO:0.80Eu3+@OA) to help better identify Level I-III fingerprint details with high resolution and contrast. The results show that the KLMO:Eu3+ and KLMO:Eu3+@OA phosphors have very promising applications in the w-LEDs and latent fingerprints (LFPs).

StarDICE

Context. The Hubble diagram of type-Ia supernovae (SNe-Ia) provides cosmological constraints on the nature of dark energy with an accuracy limited by the flux calibration of currently available spectrophotometric standards. This motivates new developments to improve the link between existing astrophysical flux standards and laboratory standards. Aims. The StarDICE experiment aims to establish a five-stage metrology chain from NIST photodiodes to stars, with a targeted accuracy of 1 mmag in griz colors. We present the first two stages, resulting in the calibration transfer from NIST photodiodes to a demonstration 150 mpixel CMOS sensor (Sony IMX411ALR as implemented in the QHY411M camera by QHYCCD). As a side-product, we provide full characterization of this camera, which we believe to be of potential interest in astronomical imaging and photometry and specifically discuss its use in the context of gravitational wave optical follow-up. Methods. A fully automated spectrophotometric bench was built to perform the calibration transfer. The sensor readout electronics was studied using thousands of flat-field images from which we derived stability, high-resolution photon transfer curves (PTC), and estimates of the individual pixel gain. The sensor quantum efficiency (QE) was then measured relatively to a NIST-calibrated photodiode, in a well-defined monochromatic light beam from 375 to 1078 nm. Last, flat-field scans at 16 different wavelengths were used to build maps of the sensor response, fully characterizing the sensor for absolute photometric measurements. Results. We demonstrated statistical uncertainty on QE below 0.001 e−/γ between 387 nm and 950 nm, the range being limited by the sensitivity decline of the tested sensor in the infrared. Systematic uncertainties in the bench optics are controlled at the level of 1 × 10−3 e−/γ. Linearity issues are detected at the level of 5 × 10−3 e−/γ for the tested camera and require further developments to fully correct. Uncertainty in the overall normalization of the QE curve (without relevance for the cosmology, but relevant to evaluate the performance of the camera itself) is 1%. Regarding the camera we demonstrate stability in steady state conditions at the level of 32.5 ppm. Homogeneity in the response is below 1% RMS across the entire sensor area. Quantum efficiency stays above 50% in most of the visible range, peaking well above 80% between 440 nm and 570 nm. Differential nonlinearities at the level of 1% are detected. A simple two-parameter model is proposed to mitigate the effect and found to adequately correct the shape of the PTC on half the numerical scale. No significant deviations from integral linearity were detected in our limited test. Static and dynamical correlations between pixels are low, making the device likely suitable for galaxy shape measurements.

Feedback between radiation and transport in photovoltaics

AbstractBy building on the generalized Hovel model, this work develops an analytical solution to unify photon recycling, light trapping, and carrier transport in solar cells. Enhanced transport due to photon recycling diffusion is considered. While photon recycling diffusion is often negligible, it can significantly support transport in cases where charge diffusion is low but radiative efficiency is high. Next, the diffusion equation is solved to determine carrier collection for planar and textured cells. Results elucidate novel features in the external quantum efficiency (EQE) curve that occur for textured cells with high absorption and limited transport. Then, the effect of limited transport on the radiative recombination of solar cells is investigated in detail. While the traditional treatment of detailed balance uses the applied voltage to calculate a cell's radiative recombination, the present approach uses the spatially resolved quasi‐Fermi‐level splitting (QFLS). The discrepancy between the models is shown to be inconsequential to performance for cells with low radiative recombination (Si) or with high mobilities (lowly doped GaAs). However, for cells with high radiative recombination and low mobility (highly doped GaAs, polycrystalline CdTe, and thin‐film perovskites), incorporating variation in QFLS in the determination of radiative recombination can become necessary for accurate photovoltaic modeling.

Effects of beam splitting on photovoltaic properties of monocrystalline silicon, multicrystalline silicon, GaAs, and perovskite solar cells for hybrid utilization

ABSTRACT Photovoltaic-thermal beam-splitting hybrid system utilizes solar energy with a high efficiency in a wider spectrum than photovoltaics. However, few studies explain the selection of solar cells or consider perovskite solar cells for the hybrid system. In this work, we studied the effects of beam splitting on the photovoltaic properties of monocrystalline silicon, multicrystalline silicon, GaAs, and perovskite solar cells with beam splitters to determine their applicability to beam-splitting hybrid systems. Transmission wavelengths of the beam splitters are 400–714 nm, 410–802 nm, 420–840 nm, and 430–1100 nm, respectively. Open-circuit voltage, fill factor, short-circuit current density, maximum power, and power conversion efficiency of solar cells with and without beam splitters were compared. Additionally, external quantum efficiency curves of the solar cells were presented to explain the trends of and to compare the preceding parameters. Results show that the Si solar cells is ineffective for the beam-splitting hybrid utilization with general beam splitters for their wide spectral response range, and the GaAs solar cell is better for its short spectral response range, and beam splitting can improve its power conversion efficiency. Meanwhile, the perovskite solar cell shows a great potential for hybrid utilization.

Research on a back-illuminated CMOS sensor for LUV imaging

The Lyman UV (LUV) band possesses several unique characteristics that make it useful to study the properties of the interstellar medium and the circum-galactic medium (CGM) surrounding nearby galaxies. MCP detectors are sensitive in the LUV band and can be used as imagers and photon counters in space missions. Instead of MCP, this paper describes a new CMOS imaging system that can be applied to astronomical observations in the LUV band. We adopted a special back-side illuminated CMOS as the image sensor. Using it, we developed a LUV imaging system based on FPGA technology. With the assistance of a synchrotron radiation platform, the properties of the CMOS imaging system were measured and calibrated within the wavelength range from 105 nm to 130 nm. By calibrating gain, photon current, electron number and photon number parameters, we derived the quantum efficiency curve for this wavelength range. Such a development provides a new method to detect and image Lyman UV radiations.

Contribution towards the selection of electron and hole transport layers for the development of highly efficient PbS colloidal quantum dot solar cell

Quantum dot solar cell (QDSC) is a promising third-generation solar cell because of the theoretical prediction that its power conversion efficiency (PCE) can reach up to 66 % because of happening of a special phenomenon like multi-exciton generation (MEG). However, the PCE of QDSCs is very low in comparison to its theoretically predicted value. One of the reasons for low PCE could be the recombination of electron-hole pairs in the quasi-neutral region (QNR). To overcome the recombination losses and improve the efficiency of QDSC, the selection of an appropriate hole transport layer (HTL) and an electron transport layer (ETL) is essential. Cuprous oxide(Cu2O) is used as HTL, tetrabutylammonium iodide treated lead sulfide (PbS-TBAI) as an active layer, tungsten trioxide (WO3) as ETL and the PCE obtained is 15.51 %. Further, the energy band diagram (EBD), quantum efficiency (QE) curve and current-voltage (J-V) curve is obtained using the SCAPS-1D simulator. Further, we have optimized our device by varying thickness of PbS-TBAI, Cu2O and WO3, defect density at Cu2O/PbS-TBAI interface and PbS-TBAI/WO3 interface, doping density of Cu2O and WO3, electron affinity of Cu2O and WO3 and the PCE obtained after optimization is 23.05 %.

Effects of ZnO nanoparticle/nanorod composite films on the performance of organic solar cells

<p indent="0mm">In past decades, organic solar cells (OSCs) have attracted much attention due to their advantages such as light weight, flexibility, variable color, adjustable band gap and roll-to-roll (R2R) manufacturing. Recently, the certificated power conversion efficiency (PCE) of single-junction OSCs has exceeded 18%, showing great potential for commercial applications. The outstanding performance of OSCs strongly depends on innovative research on the synthesis of efficient active materials. However, essential interfacial modification is also very critical because it can not only benefit charge extraction and transportation, but also effectively protect the active materials and thus improving the device performance. Therefore, various interfacial materials have been investigated intensively for highly efficient OSCs. Zinc oxide (ZnO) nanomaterials with excellent optoelectronic properties are considered to be one of the most promising candidates for electron transport layers (ETLs) of R2R printed OSCs. However, ETLs of the most common ZnO nanoparticles (NPs) inevitably have plenty of surface defects due to their high surface to volume ratio, which impairs the carrier transportation and collection. To address this concern, in this work, a composite film of ETL is designed for OSCs using the mixture of ZnO nanorods (NRs) and ZnO NPs. ZnO NRs with hexagonal crystal structure are synthesized by the solvothermal method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that the intensity of diffraction peak (002) of ZnO NRs was significantly higher than that of diffraction peak (101) and peak (101), indicating that nanorods grow along the <italic>c</italic>-axis orientation. It is also found that the diameter and length of well-crystallized ZnO NRs range from 5 to <sc>8 nm</sc> and from 15 to <sc>40 nm,</sc> respectively. The ZnO NRs are introduced as the electron transport material for OSCs with the structure of ITO/PEDOT:PSS/PM6:Y7/ZnO NPs/ZnO NPs:NRs/Al. The prepared ZnO NRs are blended with ZnO NPs to achieve an optimal surface morphology of the ETL and enhanced light capture capability of the device. ETLs with different ratios of ZnO NRs to ZnO NPs are prepared. When the mass ratio of ZnO NRs reaches 50%, the ETL becomes dense and uniform without apparent cracks and pinholes, so the resultant OSCs achieve the best performance. The best device shows a short circuit current density (<italic>J</italic>_sc)<italic> </italic>of <sc>24.30 mA cm^–2,</sc> an open circuit voltage (<italic>V</italic>_oc) of <sc>0.85 V,</sc> and a fill factor (FF) of 70.17%, corresponding to a champion PCE of 14.50%, which is higher than that of OSCs without ZnO NRs (PCE of 13.69% with <italic>J</italic>_sc<italic> </italic>of <sc>23.59 mA cm^–2, </sc><italic>V</italic>_oc<italic> </italic>of <sc>0.83 V</sc> and FF of 69.91%). Meanwhile, it is shown that the external quantum efficiency (EQE) curve of the optimal OSCs with ZnO NRs is higher than those of OSCs without ZnO NRs, which is consistent with the experimental results of <italic>J-V</italic> curve. The significant improvements attribute to the enhancement on the electron extraction and the light capture capability by the incorporation of ZnO NRs with excellent transport properties and the improved ETL morphology. Appropriately increased roughness after the incorporation of ZnO NRs also benefits the light absorption of the device. This work could come up with a new idea for the synthesis and application of ZnO-based interfacial materials in thin-film solar cells.

A Numerical Simulation for Efficiency Enhancement of CZTS Based Thin Film Solar Cell Using SCAPS-1D

In this paper we proposed a solar cell having model “Back Contact/CZTS/ZnCdS/ZnO/Front Contact”. CZTS is working as an absorber layer, ZnCdS as a buffer layer and ZnO as a window layer with back and front contacts. The Zn content was varied from 0% to 10% and bad gap was changed from 2.42 to 2.90 eV as described in the literature. The impact of this band gap variation has been observed on the performance of solar cell by using SCAPS-1D software. The efficiency was varied due to variation in bandgap of ZnCdS thin film layer. The simulation was carried out at 300K under A.M 1.5 G 1 Sun illumination. The energy bandgap diagram has been taken from SCAPS to explain the different parameters of solar cell. The effect of ZnCdS having different bandgap values was observed. Then the thickness of CZTS layer was varied to check its effect and hence at 3.0 um gave the imporved efficiency of 13.83% roundabout. After optimization of CZTS layer thickness, the effect of working temperature was examined on the performance of solar cell. The absorption coefficient variation from 1E+4 to 1E+9 cm-1 caused major effects on the characteristics parameters of solar cell along with on J-V characteristics and Quantum Efficiency curve. At 1E+9 cm-1 absorption coefficient the efficiency of solar cell boost up to 16.24%. This is the remarkable improvement in the efficiency of solar cell from 13.82% to 16.24%. After optimization of all parameters, simulation was run at 280K, having CZTS thickness of 3.5 um, with 10% content Zn in ZnCdS (2.90 eV), and absoption coefficient of 1E+9, the model efficiency reached up to 17.6% with Voc of 0.994 V, Jsc 26.1 mA/cm2 and Fill factor was 71.4%.

Understanding the Origin of Thermal Annealing Effects in Low‐Temperature Amorphous Silicon Films and Solar Cells

A detailed investigation of the effects of prolonged postdeposition annealing on the performance of amorphous silicon (a‐Si:H) solar cells and the properties of individual a‐Si:H layers that are fabricated at low temperature of 120 °C is presented. A substantial improvement in all parameters of the current–voltage curves of these solar cells is observed upon annealing, consistent with an improvement in the collection voltage of the solar cells. Modifications of p‐type layers during deposition of the solar cells are found to make no significant contribution to the annealing behavior of solar cells, while variations in the properties of n‐type and intrinsic layers contribute substantially. The results indicate that the largest contribution to the annealing effect originates from changes in the electronμτ‐product in the intrinsic absorber layer upon annealing, while changes in holeμτ‐products have a minor contribution to the annealing effect in the solar cell. Besides a lack of significant changes in the number of recombination centers upon annealing, an improvement in the external quantum efficiency curves upon annealing may be accurately reproduced in computer simulations by assuming an increase in the band mobilities of both electrons and holes.