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Hole transport layer (HTL) plays a critical role in perovskite solar cells (PSCs). We focus on the improvement of PSCs performance with MoS2 nanosheets as the anode buffer layer in the inverted photovoltaic structure. PSC with single MoS2 buffer layer shows poor performance in power conversion efficiency (PCE) and the long-term stability. By combination of MoS2 and Poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) as double-layer HTL, the PCE is improved to 18.47%, while the control device with PTAA alone shows a PCE of 14.48%. The same phenomenon is also found in 2D PSCs. For double-layer HTL devices, the PCE reaches 13.19%, and the corresponding PCE of the control group using PTAA alone is 10.13%. This significant improvement is attributed to the reduced interface resistance and improved hole extraction ability as shown by the electric impedance spectroscopy and fluorescence spectroscopy. In addition, the improved device exhibits better stability because the PCE still maintains 66% of the initial value after 500 h of storage, which is higher than the 47% of the remaining PCE from device based on single PTAA or MoS2. Our results demonstrate the potential of polymer/inorganic nanomaterial as a double-layer buffer material for PSCs. [ABSTRACT FROM AUTHOR]

Today, real-time measurement of dynamic power factor in resistance spot welding (RSW) is of increasing importance. On the basis of the welding transformer circuit model, a new method is proposed to measure the peak angle of the welding current and then calculate the dynamic power factor in each half-wave. The tailored sensing and computing system ensures that the measuring method possesses a real-time computational capacity with satisfying accuracy. Since the power factor cannot be represented via an explicit function with respect to measurable parameters, the traditional method(s) has to approximate the power factor angle with a constant phase lag angle and fails to detect its dynamic characteristics. An offline-trained embedded artificial neural network (ANN) successfully realizes the real-time implicit function calculation or estimation. A digital-signal-processor-based RSW monitoring system is developed to perform ANN computation. Experimental results indicate that the proposed method is applicable for measuring the dynamic power factor in single-phase half-wave controlled rectifier circuits. Index Terms--Dynamic power factor, feedforward neural networks (NNs), miniature Rogowski loop, silicon-controlled rectifier (SCR), voltage transformers, welding.

Two solution‐processable organic semiconductors, DFPT‐DTTR (1) and DFPbT‐DTTR (2), composed of pentafluorophenyl (FP) end‐capped 3,5‐dialkyl dithienothiophene (DTTR) core with thiophene (T) or bithiophene (bT) as π‐bridged spacers are developed and investigated for their optical, electrochemical, microstructural, and electrical properties. With more conjugated bithiophene units, compound 2 exhibits a red‐shifted UV–vis absorption band and upshifted HOMO/downshifted LUMO energy levels. According to the density functional theory, compound 2 features a more twisted molecular structure due to the intrinsic non‐coplanar blocks in the π‐backbones. Compound 1‐based organic field effect transistors exhibit efficient hole transport with mobility up to 0.48 cm2 V−1 s−1. This is one of the high mobility organic semiconductors exhibiting p‐channel characteristics based on solution‐processable small molecular FP end‐capped fused/oligothiophenes. With large and interconnected crystalline morphologies, decreased π–π stacking distance, and less steric hindrance, compound 1 exhibits two orders of magnitude higher mobility than the more distorted 2, which exhibits lower hole mobility of 1.82 × 10−3 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

The upscaling of perovskite solar cells to achieve high‐throughput and highly efficient photovoltaic devices is still challenging. In this work, spray deposition of MAPbI3‐xBrx mixed halide perovskite is achieved using a ternary channel pumping system to deposit methylammonium iodide, PbI2, and PbBr2 precursor solutions. The compositions of six kinds of perovskite films (x = 0–0.5) are manipulated by adjusting the flow rate of the syringe pump rather than through traditional methods of preparing and changing the chemical management of the halogen precursors. Large clusters in highly oriented crystalline perovskite films are fabricated as MAPbI2.91Br0.09 film (x = 0.09) with a champion power conversion efficiency (PCE) of 15.60%. When vacuum‐assisted thermal annealing is used, the optimized PCE increased further up to 17.07%. To confirm the homogeneity of the perovskite film over the large area (7 × 10 cm2), eight divided subcells with dimensions of 2.5 × 2.5 cm2 showed the highest and average PCE of 17.11% and 16.25 ± 0.77%, respectively. These findings highlight the relevance of high‐throughput screening of perovskite compositions and the versatility of scalable solution process, in which active layers are deposited by spray‐coating. [ABSTRACT FROM AUTHOR]

A novel quinoidal thienoisoindigo (TII)‐containing small molecule family with dicyanomethylene end‐capping units and various alkyl chains is synthesized as n‐type organic small molecules for solution‐processable organic field effect transistors (OFETs). The molecular structure of the 2‐hexyldecyl substituted derivative, TIIQ‐b16, is determined via single‐crystal X‐ray diffraction and shows that the TIIQ core is planar and exhibits molecular layers stacked in a "face‐to‐face" arrangement with short core intermolecular distances of 3.28 Å. The very planar core structure, shortest intermolecular N···H distance (2.52 Å), existence of an intramolecular non‐bonded contact between sulfur and oxygen atom (S···O) of 2.80 Å, and a very low‐lying LUMO energy level of −4.16 eV suggest that TIIQ molecules should be electron transporting semiconductors. The physical, thermal, and electrochemical properties as well as OFET performance and thin film morphologies of these new TIIQs are systematically studied. Thus, air‐processed TIIQ‐b16 OFETs exhibit an electron mobility up to 2.54 cm2 V−1 s−1 with a current ON/OFF ratio of 105–106, which is the first demonstration of TII‐based small molecules exhibiting unipolar electron transport characteristics and enhanced ambient stability. These results indicate that construction of quinoidal molecule from TII moiety is a successful approach to enhance n‐type charge transport characteristics. [ABSTRACT FROM AUTHOR]

The sequential deposition of a NiOx hole‐transporting layer, one‐step CH3NH3PbI3 perovskite absorber, and blended electron‐transporting layer that comprises [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) and PNDI(2OD)T2 via automated ultrasonic spray‐coating technique is demonstrated in air for planar inverted p–i–n solution‐processed perovskite solar cells. Films fabricated via laboratory‐sale spin‐coating and industrially compatible spray‐coating process, respectively, are compared with each other to optimize both the film‐coating quality and corresponding device performance. This is validated by the photovoltaic performance of prototype devices with three spray‐coated layers with the active area of 1 × 1 cm2. The champion cells achieve a power conversion efficiency of 10.09%, which is one of the highest efficiencies obtained from fully spray‐processed large‐area perovskite solar cells thus far. Furthermore, these results reinforce the feasibility of the spray‐coating methodology for the fabrication of multilayers within perovskite solar cells stack and low‐cost route toward upscaling the manufacturing alternatives to spin coating. [ABSTRACT FROM AUTHOR]