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A tandem solar cell consisting of three cells is designed and simulated by the Solar Cell Capacitor Simulator (SCAPS) program. The bandgap of the top cell absorber (Cs2AgBi0.75Sb0.25Br6) is 1.8 ev, the middle cell absorber (CH3NH3PbI3) has a bandgap of 1.55 ev), and a single-crystal silicon cell (with 1.12 ev bandgap) is selected as the bottom cell. Each of these cells were simulated and optimized separately. To improve current density in the middle cell, CuSCN is chosen as the hole-transport layer (HTL). Power conversion efficiencies (PCE) of individual Cs2AgBi0.75Sb0.25Br6, MAPbI3, and Si cells are 14.32%, 25.09%, and 25.22%, respectively; which are quite close to the results published in the literature. Consequently, the tandem structure of these cells is simulated and the optimal thicknesses for the absorber layers (as required by the current-matching condition) in a two-terminal (2T) monolithic structure is calculated. The optimized thicknesses of Cs2AgBi0.75Sb0.25Br6 and MAPbI3 absorber layers in the tandem configuration are 300 and 550 nm, respectively. The transmitted spectra of the top and middle cells are obtained using the Matlab software. Subsequently, the SCAPS numerical simulation for the 2T tandem structure gave an enhanced power conversion efficiency (PCE) of 38.9%. [ABSTRACT FROM AUTHOR]

The performance of a multi-layer honeycomb skeleton can be significantly enhanced through tandem connection, while the structure's properties can be tailored by altering the layer stacking method of the honeycomb skeleton. To investigate the impact of layer stacking methods on the mechanical properties of multilayer honeycomb skeletons, 3D printing technology was used to prepare double-layer honeycomb skeleton tandem structures with different dislocation modes in compression testing. A finite element simulation model was established to conduct quasi-static simulation research. Compared to that of a single-layer honeycomb skeleton, the energy absorption of the honeycomb skeleton tandem structure increased. The optimal bearing capacity of the honeycomb skeleton was achieved when the upper and lower layers were precisely aligned. Once dislocation occurred, both the value of average platform stress and energy absorption decreased. Then, the bearing capacity of the honeycomb skeleton tandem structures increased with an enlargement of the dislocation, reaching its maximum at the half-dislocation period. An increase in the partition thickness and stiffness led to a reduction in the dislocation-induced effects on the mechanical properties. The research results can provide theoretical and data support for the engineering application of honeycomb skeleton tandem structures. [ABSTRACT FROM AUTHOR]

To achieve high‐resolution display, dual color tandem quantum dot light emitting diodes (QD‐LED) could be candidate. This tandem QD‐LED's characteristics affected by interface of emission layer (EML)/hole transport layer (HTL) and thickness of electron transport layer (ETL). In this research, we analyzed various solvents for HTL and modulated ETL thickness. [ABSTRACT FROM AUTHOR]

For C-band wavelength-division multiplexing (WDM) transmission systems, achieving balanced output channel power is a practical goal for performance maintenance, given the moderate fiber nonlinearity and sometimes outdated control and monitoring devices in these deployed systems. To accomplish this, we propose a digital twin (DT)-based tandem neural network (NN) structure for optimizing launch power profile. The proposed structure consists of two components: an optimization NN, which generates the optimized launched channel power based on a target output power profile, and a forward DT NN, pre-trained to predict output power profile after multi-span transmission. The proposed method enables fast and efficient launch power optimization on simulated links with arbitrary channel loadings and has been validated using open-source experimental data from links with heterogeneous spans and naked amplifiers. The power profile ripple can be reduced from more than 20 dB to 1.2 dB, providing an effective solution for practical C-band WDM systems. • Optical power flatness optimization is essential for C-band systems. • Tandem neural network optimizes launch power profile for a transmission link. • Flat and tilted target output power profiles can be fast and efficient achieved. • Tandem outperforms gradient descent and inverse NN in stability and generalization. [ABSTRACT FROM AUTHOR]

Tandem structures with different subpixels are promising for perovskite‐based multicolor electroluminescence (EL) devices in ultra‐high‐resolution full‐color displays; however, realizing excellent luminance‐ and color‐independent tunability considering the low brightness and stability of blue perovskite light‐emitting diodes (PeLEDs) remains a challenge. Herein, a bright and stable blue gallium nitride (GaN) LED is utilized for vertical integration with a green MAPbBr3 PeLED, successfully achieving a Pe‐GaN tandem LED with independently tunable luminance and color. The electronic and photonic co‐excitation (EPCE) effect is found to suppress the radiative recombination and current injection of PeLEDs, leading to degraded luminance and current efficiency under direct current modulation. Accordingly, the pulse‐width modulation is introduced to the tandem device with a negligible EPCE effect, and the average hybrid current efficiency is significantly improved by 139.5%, finally achieving a record tunable luminance (average tuning range of 16631 cd m−2 at an arbitrary color from blue to green) for perovskite‐based multi‐color LEDs. The reported excellent independent tunability can be the starting point for perovskite‐based multicolor EL devices, enabling the combination with matured semiconductor technologies to facilitate their commercialization in advanced display applications with ultra‐high resolution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Upper limit efficiencies are calculated for tandem thin-film + silicon solar cells. • Output voltage scaled to the bandgap is used as a thin-film quality parameter. • Optical absorption is tied to the Tauc model for near-edge photon energies. • SQ optimization is performed for selected thin-film composition families. • Larger bandgap is required when lower quality thin films are used. We present a photon-counting simulation to evaluate the impact of top cell film quality on overall performance when designing stack tandem photovoltaic devices. We apply this model to the case where the bottom cell material is silicon in order to take advantage of the relatively low cost of manufacture already available. For the top cell, we approach material selection with an understanding that thin-film devices usually can't reach the output voltage ideality that can be achieved with optimized single crystal devices. With limited thickness for the top cell, a range of photons with energies higher than the band gap may still not be absorbed in the top cell due to the normally smaller absorption coefficients just above the bandgap energy. We use the Tauc formalism for parameterizing near-edge optical absorption and investigate the effects of film thickness and bandgap on expected efficiency values of CdTe and MALI family materials, which are already known to be good candidates for top cell thin-film devices. [ABSTRACT FROM AUTHOR]

Blue phosphorescent organic light-emitting diodes (PHOLEDs) are on the brink of commercialization for decades. However, the external quantum efficiency (EQE) and operational lifetime of PHOLEDs are not yet reached industrial standards. Here, a novel tetradentate Pt(II) emitter with a spirofluorene onto the carbazole unit that minimizes the vibration modes, corresponding to the structural relaxation during the de-excitation, called the vibration suppression effect is reported. This modification reduces the intensity of the second peak in the spectrum and Shockley-Read-Hall recombination by blocking direct hole injection into the emitter while enhancing Förster resonance energy transfer, resulting in 451 h of LT 50 (the time until a 50% decrease in initial luminance at 1000 cd m -2 ) and 25.1% of the maximum EQE (EQE max ). Thanks to the vibration suppression effect, an extremely narrow full width at half a maximum of 22 nm is obtained. In phosphor-sensitized thermally activated delayed fluorescent OLED, ultra-pure blue emission with Commission internationale de l'Eclairage (CIE) coordinates of (0.136, 0.096) is obtained with 28.1% of EQE max . Furthermore, 50.3% of the EQE max and 589 h of LT 70 are simultaneously recorded with the two-stack tandem PHOLED, which is the highest EQE max among 2-tandem and bottom-emission PHOLEDs with CIEy < 0.15., (© 2024 Wiley‐VCH GmbH.)

Tandem organic solar cells (OSCs), consisting of more than one (usually two) sub-cells, stacked and connected by a charge recombination layer (i.e., interconnecting layer (ICL)), are highly promising to boost OSC efficiency. The ICL plays a critical role in regulating the performance of tandem device. Here, we report ZnO or C60 as a simple ICL, modified then, by a PEDOT:PSS layer, can act as an efficient ICLs in tandem device to achieve a significant increase in performance compared to single sub-cell. After optimized optical properties of MEH-PPV:PC70BM and P3HT:PC70BM sub-cells by varying the annealing temperature, these ICLs are used to connect photoactive layers. For all tandem devices, we showed an improvement in optical properties, especially in the ground and excited states compared to optimized single sub-cells. The degree of improved performance in tandem devices is attributed to the connection which provides each ICL. For fully optimized tandem, based on C60 ICL, reached ~78% enhancement in charge transfer compared to the bottom sub-cell and 82% compared to the top sub-cell, obtained for λemission = 650 nm. [ABSTRACT FROM AUTHOR]

Inspired by the tandem structure can be used as an effective approach to improving the performance of optoelectronic devices such as solar cells and organic light emitting diodes, a series of mechanical sensors with high performance were fabricated on a flexible sheet (thickness, less than $300~\mu \text{m}$) based on tandem structures. In our designed tandem structure models, the single sensing unit consisting of one single carbon fiber beam presents nonlinear behavior when responding to force stimuli. Thus, the initial resistance and resistance change value of the tandem mechanical sensors could be enhanced by increasing the number of sensing units to lengthen the current path through carbon fiber beams and enable the sensor to respond to subtle force after preloading a large force. Moreover, the tandem mechanical sensors can measure force quantitatively due to the corresponding relationship between the resistance change rate and the loading force. These combined advantages of the tandem mechanical sensors were also demonstrated by the successful application in weighed, softness discrimination and texture discrimination, implying that these mechanical sensors could be used as mechanoreceptors like a finger touching in monitoring daily life sensations. [ABSTRACT FROM AUTHOR]

We report high performance deep red tandem OLEDs suitable for automotive lighting applications. We developed a deep red phosphorescent emitter that has an intrinsic photoluminescent (PL) peak wavelength at 639 nm and a photoluminescent quantum yield PLQY of 0.80. A low‐voltage red host (LVRH) material was developed to match this emitter, which enables a single‐unit, bottom emission device to reach 2,000 cd/m2 with an external quantum efficiency (EQE) of 25.8%, bias voltage of 3.7 V, and LT95 of 6,000 hrs. A 3‐unit device incorporating this emissive system along with a novel charge‐generation layer (CGL) was fabricated and its device structure was optimized by tuning the hole transport layer (HTL) thickness. The device achieved a current efficiency of 39 cd/A, overall EQE of 77%, LT95 of 46,000 hrs, and bias voltage of 9.9 V at 2,000 cd/m2. This tandem device also reaches a deep red chromaticity with a peak wavelength of 641 nm, and CIE (X, Y) = (0.706, 0.293). The LT95 of the same device at 85 °C was 9,700 hr at 2,000 cd/m2. Such a deep red OLED is desirable for automotive lighting applications. [ABSTRACT FROM AUTHOR]

Modern lighting requires high efficiency and long lifetime simultaneously. In this paper, highly efficient white organic light emitting diodes (WOLEDs) are demonstrated based on a modified hybrid tandem structure constructed with a phosphorescent yellow‐red unit using an exciplex host and a blue‐red unit based on a thermally activated delayed fluorescence (TADF) blue emitter, and the devices are properly built with internal and external light extraction structures. The resulting four‐color WOLED exhibits an external quantum efficiency and luminous efficacy of 126.2% and 150.7 Lm W−1, respectively, and the color rendering index is close to 80 at a brightness of 1000 cd m−2. This device also shows a very good color stability with increasing luminance up to 15 000 cd m−2 and there is only a small angular color variation for viewing angles changing from 0° to 70°. The T50 lifetime (defined as the time corresponding to 50% decrease in luminance from an initial value) of the WOLED at an initial luminance of 1000 cd m−2 is extrapolated as 12 600 h. [ABSTRACT FROM AUTHOR]

We report here high performance deep red OLED devices for automotive lighting applications, through optimizing the organic stacks in a tandem structure. We first developed a deep red phosphorescent emitter that has a PL peak wavelength at 639 nm. A 2‐unit device incorporating this emitter along with a novel charge‐generation layer, was tuned to achieve an external quantum efficiency of 48%, a current efficiency of 26 cd/A, LT95 of 11,000 hrs, and a bias voltage of 8.2 V at 2,000 cd/m2. This tandem device reaches a deep red chromaticity with a dominant wavelength of 625nm, and CIE (X, Y) = (0.70, 0.30), as well as a near‐Lambertian emission pattern. [ABSTRACT FROM AUTHOR]

Copyright of Bundesgesundheitsblatt - Gesundheitsforschung - Gesundheitsschutz is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The power conversion efficiency (PCE) of organic photovoltaics (OPVs) has exceeded 18% with narrow bandgap, non-fullerene materials Y6 or its derivatives when used as an electron acceptor. The PCE improvement of OPVs is due to strong photon harvesting in near-infrared light range and low energy loss. Meanwhile, ternary strategy is commonly recognized as a convenient and efficient means to improve the PCE of OPVs. In this review article, typical donor and acceptor materials in prepared efficient OPVs are summarized. From the device engineering perspective, the typical research work on ternary strategy and tandem structure is introduced for understanding the device design and materials selection for preparing efficient OPVs.

• Development of an analytical model for four terminal Al x Ga 1-x As/CIGS tandem cell. • The model considers both surface geometries: planar and randomly textured. • Textured light trapping can reduce the optimum thickness of AlGaAs from 5 to o.5 µm. • Efficiency of tandem cell optimized 37% for 0.35 < x < 0.48 in Al x Ga 1-x As. • For the high efficiencies (>34%), TDD in the AlGaAs cells should not exceed 107 cm−2. In this work, a four-terminal Al x Ga 1-x As/CuInGaSe 2 tandem structure has been proposed by analytical model. To develop this model, the real experimental data for CIGS and Al x Ga 1-x As cells has been used. Conversion efficiency of optimized Al 0.42 Ga 0.58 As/CuInGaSe 2 tandem solar cell achieved to 37.1%. Our model estimates the optimum bandgap of Al x Ga 1-x As as top cell is in the range of 1.85–2 eV. The optimized thickness of Al 0.31 Ga 0.69 As in tandem structure is 5 μm, which decreases to 0.5 μm by light trapping technique. Moreover, we extended our model by the consideration of threading dislocation density in Al x Ga 1-x As layer. [ABSTRACT FROM AUTHOR]

We have developed high efficiency tandem quantum‐dot light‐emitting diode (QLED) by using oxide n‐p charge generation junction (CGJ). The tandem QLED with oxide n‐p CGJ exhibits the current efficiency as high as over 120 cd A−1. The oxide n‐p CGJ shows good Ohmic behavior under forward and reverse bias. It is obvious that the reverse current density is nearly equal to the forward current density, which suggest the efficient charge generation in the oxide n‐p CGJ. In this work, we demonstrated a 4‐inch AMQLED display using high efficiency tandem QLED with oxide n‐p CGJ. [ABSTRACT FROM AUTHOR]

Abstract To protect the quantum-dots (QDs) from dissolving by the solvents of upper hole transporting layer (HTL) in inverted structure, we took a thorough study on the influence of HTL materials and solvents on the photoluminescence (PL) intensity of QDs. The experimental results confirm that the QDs layer can survive after solution processing by carefully selecting the suitable HTL material and the solvent. Second, after overall estimating the wetting enhancement ability and the additive residue of several different additives, IPA was selected as the additive to facilitate the deposition of a hydrophilic poly(ethylenedioxythiophene)/polystyrenesulfonate (PEDOT:PSS) hole injection layer (HIL) on top of hydrophobic HTL layer. Finally, to obtain efficient inverted tandem QLEDs, a solution-processable interconnecting layer (ICL) based on PEDOT/ZnO is developed. The proposed ICL and the developed fabrication methods allow for realization of efficient inverted tandem QLEDs for next generation display and lighting applications. Graphical abstract Image 1 Highlights • Photoluminescence intensity was improved by solving the QD dissolving issue in inverted QLED. • IPA was used to improve the deposition quality of PEDOT. • A solution-processable interconnecting layer (ICL) based on PEDOT/ZnO was developed. • Solution processed QLED with inverted tandem structure was demonstrated based on ICL. [ABSTRACT FROM AUTHOR]

Abstract To realize energy-saving and environmental green illumination by simplified white organic light-emitting devices (WOLEDs) structure and fabricate process, herein, we successfully fabricate a novel simplified efficient WOLED structure using energy transfer from interface exciplexes to complementary color dyes as undoped ultrathin emissive layers (UEMLs) based on tandem OLEDs structure. (Acetylacetonato)bis[2-(thieno[3,2- c ]pyridin-4-yl)phenyl]iridium(III) (PO-01) and iridium(III) bis[(4,6-difluorophenyl)-pyridinato- N ,C2′]-picolinate (FIrpic) are applied as yellow and blue UEMLs, respectively. Particularly, the designed WOLED with Commission Internationale De L'Eclairage chromaticity coordinate (0.36, 0.41) obtaining a peak of 41.5 cd/A (EQE = 18.59%) without light out-coupling technology, achieving high current efficiency among reported WOLEDs all emitters applied UEMLs. Moreover, the designed white OLEDs generally emit warm white spectrum with low correlative color temperature of 3686 K–4700 K, which show are available for healthy illumination. Therefore, we believe our work help to further develop ideal simplified WOLEDs structure and fabricate process for energy-conservation and environment-friendly healthy illumination with high efficiency, simplified fabrication, low reagent consumption and cost, simultaneously. Graphical abstract Image 1 Highlights • Highly simplified efficient tandems WOLEDs using energy transfer from interface exciplexes are successfully fabricated. • High current efficiency of 41.5 cd/A (EQE = 18.59%) is achieved among reported WOLEDs all emitters applied undoped UEMLs. • The WOLEDs generally emit warm white spectrum with low CCT of 3686 K–4700 K, which are available for healthy illumination. [ABSTRACT FROM AUTHOR]

Abstract: White quantum dot light‐emitting diodes (WQLEDs) with different structures are developed. By mixing red (R), blue (B) and green (G) quantum dots (QDs) together, the optimal WQLEDs exhibit a peak current efficiency (CE) of 22.54 cd/A and an external quantum efficiency (EQE) of 7.07%. The relatively poor performance is due to the efficient nonradiative Förster resonant energy transfer (FRET) among B‐, G‐ and R‐QDs. To address this issue, tandem WQLEDs are developed. By stacking the blue and the yellow QLEDs, the two‐unit tandem WQLEDs exhibit a peak CE of 30.3 cd/A and a maximum EQE of 15.2%. To further improve the color stability and the efficiency, the R/G/B three‐unit tandem WQLEDs are developed, which exhibit an impressive CE of 55.06 cd/A, a high EQE of 23.88% and a high luminance of 65690 cd/m2, which are the highest values ever reported. Moreover, the optimal tandem WQLED exhibits a high color stability, a pure white color with a 1931 Commission International de I'Eclairage (CIE) coordinate of (0.33, 0.34) and a color rendering index of 80. The demonstrated tandem WQLEDs, with high efficiency, pure white color, high color stability and high color‐rendering, would be promising candidates for next generation solid‐state lighting and full‐color display. [ABSTRACT FROM AUTHOR]

Abstract The 8-hydroxyquinolinato lithium (Liq)|Ag system has been evaluated as the electron-injection layer for the MoO x | N,N′-di (1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) charge-generation layer in tandem organic light-emitting diode (OLED) devices. From current-voltage studies of single-stack devices, it is determined that Liq is a relatively poor electron-transport material. However, Liq is found to be useful as an electron-injection layer with activation by Ag. Efficient tandem devices have been obtained using Liq|Ag as the electron-injection layer adjacent to the MoO x |NPB charge-generation layer, where the optimal Ag thickness is about 20–40 Å and the activation of Liq can be seen with as little as 1 Å of Ag. Graphical abstract Image 1 Highlights • The Liq|Ag system was evaluated as the EIL for the MoO x |NPB CGL in tandem OLED devices. • Liq was found to be a relatively poor ETL compared to Bphen. • Liq was found to be effective as an EIL up to 20 Å with an overlayer of Ag. • Efficient tandem devices were obtained where the optimal Ag thickness is about 20 Å. [ABSTRACT FROM AUTHOR]

Organic polymer solar cells (PSCs) have attracted increasing attention due to light weight, low cost, flexibility and roll-to-roll manufacturing. However, the limited light harvest range of the photoactive layer greatly restrains the power conversion efficiency (PCE) enhancement. In order to expand the light absorption range and further enhance the PCE of the PSCs, tandem structures have been designed and demonstrated. In tandem solar cell, the intermediate layer (IML) plays a critical role in physically and electrically connection of the two subcells. Herein, we apply titanium (diisopropoxide) bis(2,4-pentanedionate) (TIPD) as both electrode modification layer and intermediate layer to investigate the feasibility in inverted tandem polymer solar cells. The same photoactive layers of PTB7-Th:PC71BM are adopted in both front and rear subcells to simplify the evaluation of effectiveness of TIPD layer in tandem structures. By modulating the treatment condition of IML and the thickness of photoactive layer, efficient inverted tandem PSCs have been achieved with minimized voltage loss and excellent charge transportation, giving a best Voc of 1.54 V, which is almost two times that of the single bulk heterojunction (BHJ)-PSC (0.78 V) and an enhanced PCE up to 8.11%. [ABSTRACT FROM AUTHOR]

Quantum-dot light-emitting diodes (QLEDs) are promising candidates for next generation displays. White QLEDs which can emit red, green and blue colors are particularly important; this is because the combination of white QLEDs and color filters offers a practical solution for high-resolution full-color displays. In this work, we demonstrate all-solution processed three-unit (red/green/blue) white tandem QLEDs for the first time. The white tandem devices are achieved by serially connecting the red bottom sub-QLED, the green middle sub-QLED and the blue top sub-QLED using the inter-connecting layer (ICL) based on ZnMgO/PEDOT:PSS heterojunction. With the proposed ICL, the two-unit tandem QLEDs exhibit a high current efficiency of 22.22 cd/A, while the three-unit white QLEDs exhibit evenly separated red, green and blue emission with a CIE coordinate of (0.30, 0.44), a peak current efficiency of 4.75 cd/A and a high luminance of 4206 cd/m2. Displays based on the developed white QLEDs exhibit a wide color gamut of 114% NTSC. This work confirms the effectiveness of the proposed ZnMgO/PEDOT:PSS ICL and the feasibility of making all-solution processed tandem white QLEDs by using the proposed ICL. [ABSTRACT FROM AUTHOR]

In this article, with the help of a one dimensional solar cell simulator, we have assessed different performance parameters of a lead free CH 3 NH 3 SnI 3 /GeTe Tandem solar cell. The performance parameters in terms of open circuit voltage (V oc), short circuit current density (J sc), fill factor (FF) and photo conversion efficiency (PCE) have been investigated for different thickness of absorber layer, acceptor concentration, defect density and series/shunt resistance and compared with a single junction solar cell. Incorporation of GeTe as a secondary absorber layer improves the performance of the solar cell by increasing photon absorption rate. Using Cu 2 O as a hole transport layer, formation of a quantum well takes place which further enhances the photon absorption rate and hence solar cell performance. The optimized tandem cell with hole transport layer shows 28 %, 9 %, 19 % and 12 % improvement in V oc , J sc , FF and PCE compared to the single junction solar cell without hole transport layer. [ABSTRACT FROM AUTHOR]

The use of a black silicon (b-Si) interlayer is a promising solution for improving the optical properties of crystalline Si/perovskite solar cells. Optical numerical simulation of the crystalline Si/b-Si/perovskite structures can efficiently optimize their parameters at the initial tandem solar cell design stage. In this work, the optical properties of these structures were modeled using the transfer matrix method, where an array of cone-like nanoneedles of the b-Si interlayer is approximated as a homogeneous optical medium, for which the effective complex refractive index is the weighted average of those for Si and perovskite. Analytical equations are obtained for tandem structures' reflection, transmission, and absorption. The simulated reflectance spectra of the structures were compared with those of structures without the b-Si layer, as well as with experimental data. Numerical calculations and experiments confirm that nanotexturing significantly improves the optical properties of tandem structures. In addition, the nanotextured tandem structures have a wide-angle antireflective characteristic at incidence angles less than 60°, indicating their omnidirectional light-trapping capability. The proposed simulation model satisfactorily describes the optical behavior of crystalline Si/b-Si/perovskite tandem structures and can be used to estimate their optical properties depending on various parameters. As a demonstration, a numerical analysis was performed to study the effect of the b-Si interlayer thickness on the reflection of the tandem structure. [Display omitted] • The tandem structures in our work consists of a Si wafer and perovskite layer with a black Si interlayer. • Optical simulation was carried out using the transfer matrix method and Brüggemann approximation. • The reflectance spectra of the structures are compared with those of the structures without black Si interlayer. • The simulation results agree satisfactorily with the data of experimental investigations. [ABSTRACT FROM AUTHOR]

Although renewable solar power plants are rapidly proliferating, high cost and the intermittent availability of solar power are still significant barriers for its penetration into the energy grid system. Concentrating solar power (CSP) offers an attractive alternative due to its integration with cost-effective thermal energy storage systems. To further reduce the cost of CSP, it is imperative to operate the plants at higher temperatures for enhanced efficiency. One of the key components for next-generation high-temperature CSP is the solar absorbing coating materials. In this work, we have developed tandem-structured solar absorbing layers with CuFeMnO 4 and CuCr 2 O 4 black oxide nanoparticles (NPs). These tandem structures exhibited a remarkably high solar-to-thermal conversion efficiency, or figure of merit (FOM), of 0.903, under the condition of 750 °C operating temperature and a solar concentration ratio of 1000. More importantly, the coating showed unprecedented durability, as demonstrated from long-term isothermal annealing at 750 °C in air as well as rapid thermal cycling between room temperature and 750 °C. Our results suggest that the tandem black oxide coating is suitable to meet the stringent demand of next-generation high-temperature CSP systems. The coating materials synthesis, structures, optical as well as thermal properties will be discussed. [ABSTRACT FROM AUTHOR]

A pn-tandem dye-sensitized solar cell ( pn-DSC) was prepared with three different sensitized dyes CBZ Dimer (CBZD), C343, and SQ in two different compartments of the n-type or p-type cells. The constructed tandem solar cell was exhibited considerable improvement in experimental pn-DSCs parameters, open-circuit voltage, short-circuit current, fill factor, etc. These results were achieved under air mass 1.5 illumination with three different sensitized dyes in the upper and lower compartment of the pn-DSCs. These results demonstrate a complementary absorption among the two photoelectrodes in the pn-DSCs is a good approach to the efficient and low cost pn-DSCs. [ABSTRACT FROM AUTHOR]

Copyright of Kobunshi Ronbunshu is the property of Society of Polymer Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An inverted tandem quantum-dot light-emitting diode (QLEDs) is demonstrated using solution processed charge generation layers (CGLs) for the first time. The tandem QLEDs with the CGL, consisting of green QDs (G-QDs) for bottom and red QDs (R-QDs) for top cells, exhibited yellow emission with current efficiency of 15.9 cd/A at 1,000 cd/m2. [ABSTRACT FROM AUTHOR]

Two 3-stack tandem white OLEDs devices with blue-yellow-blue and blue-blue-yellow structures with fluorescent blue and yellow phosphorescent materials were investigated about various performances for display applications. We report CIE coordinates of (0.335, 0.313) and 23.6 % EQE (external quantum efficiency) at 1000 cd/m2 in blue-blue-yellow structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly efficient room light tandem DSSCs are fabricated using a simple method. • Cobalt redox couples and Y123 dyes are utilized in these cells. • TiO 2 layer thicknesses of the top and bottom cells are regulated. • Both light harvest and charge transfer can be improved simultaneously. • The energy conversion efficiency as high as 33.98% is reached under 2000 lx. To fabricate dye-sensitized solar cells (DSSCs), the variation of TiO 2 film thickness elicits contrary effects on the light-harvesting and charge transfer, thereby affecting cell performance. To compromise the TiO 2 thickness on the two effects, tandem DSSCs constructed by stacking two cells in series were proposed herein. Cells with high transparent photoelectrodes and counter electrodes were employed as the top cells; thus, the light unabsorbed by the top cells can be transmitted through, and harvested by the bottom cells. Furthermore, cobalt redox couple was adopted to decrease the light loss caused by absorption of the electrolyte. By regulating the film thicknesses of the top and bottom cells, both light harvest and charge transfer performance can be improved simultaneously, thereby, achieving a conversion efficiency as high as 33.98% under 2000 lx fluorescent lighting. This efficiency is much higher than the value (26.57%) obtained by the single cell. The tandem structure can also be applied under sunlight conditions, which can increase the efficiency from 9.27% to 11.31%. [ABSTRACT FROM AUTHOR]

The efficient CO 2 photoreduction device with internal electric field is realized by introducing a layer tandem structure made up of g-C 3 N 4 and an inorganic lead-perovskite (CsPbBr 3). The device satisfies full artificial photosynthesis of CO 2 conversion and exhibits good stability. [Display omitted] • The efficient CO 2 photoreduction device is constructed based on CsPbBr 3 perovskite. • Tandem structure of CsPbBr 3 /g-C 3 N 4 promotes directional charge-carrier migration. • The photo-CO yield rate is 238.7 μmol m-2 h−1 under a humid gaseous CO 2 system. The design of efficient photocatalytic devices is of great significance to achieve low-cost carbon dioxide reduction into solar fuels. Herein, directional charge-carrier migration is realized by introducing a CO 2 reduction device with a tandem structure made up of g-C 3 N 4 and an inorganic lead-perovskite (CsPbBr 3). This photocatalytic device shows a significantly increased CO 2 photoreduction rate in a humid gaseous CO 2 system when compared to the parental g-C 3 N 4 layer. This "full artificial photosynthesis" thereby generates fuel molecules and oxygen from water and CO 2, only, without any co-catalysts or sacrificial agents. To our surprise, the device maintains greater than 90% of the CO production yield after 5 days continuous irradiation. The existence of internal electric field is confirmed, which drive the directional movement of photogenerated charge-carriers with the perovskite being reductive, while the carbon nitride with its enormous oxidation stability is covering the oxidation processes. This represents a promising possibility for the practical application of CO 2 photoreduction with scalable devices. [ABSTRACT FROM AUTHOR]

In order to perform the structural characterization of Si thin-film solar cells having submicron-size rough textured surfaces, we have developed an optical model that can be utilized for the spectroscopic ellipsometry (SE) analysis of a multilayer solar cell structure consisting of hydrogenated amorphous silicon (a-Si:H) and microcrystalline silicon (μc-Si:H) layers fabricated on textured SnO 2 :F substrates. To represent the structural non-uniformity in the textured structure, the optical response has been calculated from two regions with different thicknesses of the Si layers. Moreover, in the optical model, the interface layers are modeled by multilayer structures assuming two-phase composites and the volume fractions of the phases in the layers are controlled by the structural curvature factor. The polarized reflection from the μc-Si:H layer that shows extensive surface roughening during the growth has also been modeled. In this study, a state-of-the-art solar cell structure with the textured μc-Si:H (2000 nm)/ZnO (100 nm)/a-Si:H (200 nm)/SnO 2 :F/glass substrate structure has been characterized. The μc-Si:H/a-Si:H textured structure deduced from our SE analysis shows remarkable agreement with that observed by transmission electron microscopy. From the above results, we have demonstrated the high-precision characterization of highly-textured μc-Si:H/a-Si:H solar cell structures. [ABSTRACT FROM AUTHOR]

Abstract: The quantum dots (QD) and quantum rods (QR) of different sizes, shapes, and crystalline phases are synthesized by modified solvothermal method spontaneously employed stirring system and controlled internal applied pressure. The tandem structure of QDs and QRs as well as tetrapods is formed on hierarchical porous titania photoanode by means of electrophoretic deposition. A tremendous enhancement in efficiency of the cell is obtained in samples synthesized at 220 °C for 24 h due to the formation of tandem structure, utilization of Cu2S/CNT composite cathode, co-sensitization of CdS and CdSe, and beneficial role of QRs in electron lifetime. Smaller size QDs with higher band gaps penetrate deeper through the macro-channels of the hierarchical porous structure, while the QRs and tetrapods with lower band gaps are placed on upper layers. Although the charge injection is improved in smaller QDs, the electron lifetime in QRs is longer mainly due to the higher absorption cross section, proper charge separation, introduction of quasi-one dimensional route for charge transport through QRs, and higher surface area available for regeneration with electrolyte. The cell shows the efficiency of 1.05% with J SC of 4.48 mA cm−2, V OC of 0.45 V, and fill factor of 0.52. [Copyright &y& Elsevier]

Abstract: Polymer solar cells have many intrinsic advantages, such as their light weight, flexibility, and low material and manufacturing costs. Recently, polymer tandem solar cells have attracted significant attention due to their potential to achieve higher performance than single cells. This trend article intends to provide the latest progress in polymer tandem solar cell technology with a focus on active layer materials and interfacial materials for sub-cell interconnection. Following an introduction of the structure and current status of polymer tandem solar cells, this article will review polymers which have been, and could be used, for tandem solar cells. Furthermore, this article will discuss the interconnecting layer consisting of p- and n-type interfacial layers, which is equally critical for polymer tandem solar cells. Finally, because tandem solar cell measurements are more complicated than that of single solar cells, this article will also address polymer tandem solar cell measurement issues. [Copyright &y& Elsevier]

High capacitance and high output voltage are two important research focuses of electrochemical supercapacitors. Herein we present two novel designs (laminated and tandem) of coin-cell supercapacitors based on a textile coated with active material. The fabric electrodes were prepared by dipping the non-woven cloth into a dispersion of carbon nanotubes and subsequent MnO2 electrodeposition. In the lamination configuration, several pieces of active-material-coated cloth were laminated to construct individual electrodes that enable fold-increased areal capacitances and excellent cycling stability. In the tandem structure, individual cells with solid-state electrolyte (polyvinyl alcohol/H3PO4) sandwiched between the fabric electrodes were stacked together to form a single device. The assembled device composed by ten unit cells was demonstrated to drive four LED digital screens in series with 10 V output. [ABSTRACT FROM AUTHOR]

A tandem-structure sensitized solar cell, comprising different inorganic semiconductor quantum dots (QDs) as sensitizers in two different compartments, has been designed for the first time with the aim of extending the light-absorption range of current technologies. In this system, the CdS/CdSe co-sensitized quantum-dot solar cell (QDSC) is in the upper part, whereas the PbS/CdS co-sensitized QDSC is in the lower part; these are connected in parallel with each other. In the middle of the tandem solar cell, a Cu2S mesh counter electrode is employed. By optimizing the electrode thickness and QD-deposition time, short-circuit photocurrent density values of as high as 25.12 mA cm−2 have been achieved; this value is nearly equal to the sum of the two constituent QD-sensitized devices and gives rise to a solar power-conversion efficiency of 5.06 %. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE)-based gas sensors have attracted significant attention due to their high selectivity, low power consumption, and minimum maintenance requirements. However, it is challenging to find low-cost, environmentally friendly materials and simple device fabrication processes for large-scale applications. Herein, we report self-powered thermoelectric hydrogen (TEH) sensors based on bismuth sulfide (Bi 2 S 3 ) fabricated from a low-cost Bi 2 S 3 TE layer and platinum (Pt) catalyst. When working at room temperature, the monomorphic-type TEH sensor obtained an output response signal of 42.2 μV with a response time of 17 s at a 3% hydrogen atmosphere. To further improve device performance, we connected the patterned Bi 2 S 3 films in series to increase the Seebeck coefficient to -897 μV K -1 . For comparison, the resulting N tandem-type TEH sensor yielded a distinguished output voltage of 101.4 μV, which was greater than the monomorphic type by a factor of 2.4. Significantly, the response and recovery time of the N-tandem-type TEH sensor to 3% hydrogen were shortened to 14 and 15 s, respectively. This work provides a simple, environmentally friendly, and low-cost strategy for fabricating high-performance TEH sensors by applying low-cost Bi 2 S 3 TE materials.

Tandem structured dye-sensitized solar cells (DSSCs) can take full advantage of sunlight, effectively broadening the absorption spectrum of the cell, resulting in a higher open circuit voltage or short circuit current than that of the conventional DSSC with single light absorber. The theoretical maximum efficiency is therefore suggested to be over the Schottky-Queisser limit of 33%. Accordingly, tandem design of DSSC is thought to be a promising way to break the performance bottleneck of DSSC. Besides, the tandem designs also broaden the application diversity of DSSC technology, which will accelerate its scale-up industrial application. In this paper, we have reviewed the recent progress on photo-electrochemical applications associated with kinds of tandem designs of DSSCs, in general, which are divided into three kinds: 'n-type DSSC + n-type DSSC,' 'n-type DSSC + p-type DSSC' and 'n-type DSSC + other solar conversion devices.' The working principles, advantages and challenges of these tandem structured DSSCs have been discussed. Some possible solutions for further studies have been also pointed out together. [ABSTRACT FROM AUTHOR]