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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]

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]

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]

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]

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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: 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]

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]

Interband tunneling in semiconductors [1, 2] is one of the clearest manifestations of quantum mechanics in electronic devices. In the case of interband tunneling in a heavily doped PN junction, in reverse bias, electrons tunnel from the filled states in the valence band to the empty states in the conduction band. Under forward bias, tunneling current is observed when electrons tunnel from filled states in the conduction band to empty states in the valence band, as shown in Fig. 8.1. As the conduction band on the n-side becomes biased higher in energy than the valence band, states are not available for electrons to tunnel into. As a result, the current decreases, leading to a characteristic negative differential resistance regime. [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]

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]

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]

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]

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]

Hybrid organic–inorganic perovskite (HOIP) photovoltaics have emerged as a promising new technology for the next generation of photovoltaics since their first development 10 years ago, and show a high-power conversion efficiency (PCE) of about 29.3%. The power-conversion efficiency of these perovskite photovoltaics depends on the base materials used in their development, and methylammonium lead iodide is generally used as the main component. Perovskite materials have been further explored to increase their efficiency, as they are cheaper and easier to fabricate than silicon photovoltaics, which will lead to better commercialization. Even with these advantages, perovskite photovoltaics have a few drawbacks, such as their stability when in contact with heat and humidity, which pales in comparison to the 25-year stability of silicon, even with improvements are made when exploring new materials. To expand the benefits and address the drawbacks of perovskite photovoltaics, perovskite–silicon tandem photovoltaics have been suggested as a solution in the commercialization of perovskite photovoltaics. This tandem photovoltaic results in an increased PCE value by presenting a better total absorption wavelength for both perovskite and silicon photovoltaics. In this work, we summarized the advances in HOIP photovoltaics in the contact of new material developments, enhanced device fabrication, and innovative approaches to the commercialization of large-scale devices. [ABSTRACT FROM AUTHOR]

Three-stack tandem white OLEDs made with fluorescent blue and phosphorescent red and yellow-green materials are reported with 51 lm/W efficacy at 1000nit without out-coupling, 7.4 V driving voltage, and 37,000hr lifetime at 3000nit. With internal and external our-coupling in this device, 100 lm/W efficiency is achieved. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]