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Environmentally friendly and efficient organic photovoltaic (OPV) devices played a significantly essential role in commercial applications. Herein, The PM6:TBFCl50-BDD:IT-4F-based ternary device was fabricated by using non-halogen solvent o-xylene (o-XY), and...

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In recent years, ternary organic photovoltaic cells (OPVs) have been dedicated to improving power conversion efficiency (PCE) by broadening optical absorption spectra. Ternary OPVs with different poly[thieno[3,2-b]thiophene-2,5-diyl-alt-4,9-bis(4-(2-decyltetradecyl)thien-2-yl)naphtho[1,2-c:5,6-c’]bis[1,2,5]thiadiazole-5,5′-diyl] (PTT-DTNT-DT) doping concentrations were designed and the effect of PTT-DTNT-DT as a complementary electron donor on the performance of OPVs was investigated. The optimized PCE of OPVs was increased from 3.42% to 4.66% by doping 20 wt % PTT-DTNT-DT. The remarkable improvement in the performance of the ternary device is mainly attributed to the sharp increase in the short-circuit current density and fill-factor. The major reasons have been systematically studied from atomic force microscopy, electrochemical impedance spectroscopy, surface energy, space charge limited current and photocurrent behavior. It has been found that the separation of excitons and the transportation of charge are enhanced while light absorption is increased, and the charge recombination also decreases due to the optimization of the cascade energy level and the morphology of the ternary active layer. The results show that it is feasible to improve the performance of ternary OPVs by their complementary absorption.

A novel (E)-5-(2-(5-alkylthiothiophen-2-yl)vinyl)thien-2-yl (TVT)-comprising benzo[1,2-b:4,5-b’]dithiophene (BDT) derivative (BDT-TVT) was designed and synthetized to compose two donor-acceptor (D-A) typed copolymers (PBDT-TVT-ID and PBDT-TVT-DTNT) with the electron-withdrawing unit isoindigo (ID) and naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole (NT), respectively. PBDT-TVT-ID and PBDT-TVT-DTNT showed good thermal stability (360 °C), an absorption spectrum from 300 nm to 760 nm and a relatively low lying energy level of Highest Occupied Molecular Orbital (EHOMO) (−5.36 to –5.45 eV), which could obtain a large open-circuit voltage (Voc) from photovoltaic devices with PBDT-TVT-ID or PBDT-TVT-DTNT. The photovoltaic devices with ITO/PFN/polymers: PC71BM/MoO3/Ag structure were assembled and exhibited a good photovoltaic performance with a power conversion efficiency (PCE) of 4.09% (PBDT-TVT-ID) and 5.44% (PBDT-TVT-DTNT), respectively. The best PCE of a PBDT-TVT-DTNT/PC71BM-based device mainly originated from its wider absorption, higher hole mobility and favorable photoactive layer morphology.

A conjugated polyelectrolyte poly (9,9-bis(3′-[(N,N-dimethyl)-N-ethylammonium]-propyl)-2,7-fluorene dibromide) (PFBr) with the feature of environmental friendliness and cheapness was successfully used in polymer solar cells (PSCs) as the cathode interfacial layer (CIL). And we successfully demonstrate that the PFBr can build interfacial dipoles at the CIL/cathode interfaces, leading to reduce cathode work functions and improve open-circuit voltages, which decrease interfacial energy loss at the cathode. It not only improves the electron transfer efficiency but also inhibits the charge carrier recombination at the contact interface. Impedance spectra revealed that the optimal device with the smallest charge transport time constant of 2.83 microseconds was achieved under the concentration of 2 mg mL −1 of PFBr, which suggests efficient electron transport on the interface between the organic active layer and the indium tin oxide cathode. Moreover, as a consequence, the power conversion efficiency of the PSCs increases to 3.83% (with PFBr as CIL) from 1.89% (without any CIL), based on the poly(3-hexylthiophene) and [6,6]-phenyl C 61 -butyric acid methyl ester bulk heterojunction active layer. Therefore, our observation can demonstrate PFBr is a prospective candidate as CIL for constructing low-cost, largearea, and flexible PSCs. KEYWORDS cathode interfacial layer, electrochemical impedance spectroscopy, PFBr, polymer solar cells, scanning Kelvin probe microscope 1 | INTRODUCTION Photovoltaic technology provides an environmentally friendly and sustainable power supply for overcoming the global energy crisis. 1,2 In particular, bulk heterojunction polymer solar cells (PSCs) have attracted great attention during recent decades, owing to the excellent merits of lightweight, flexible low-cost, and large-area devices through solution processing. 3-5 Recent great progresses have been made by controlling the active layer morphology by posttreatment methods, 6 developing novel interfacial layers, 7 active materials, and new device structures with enlarged donor/acceptor interface. 8 As known, there are 2 main device structures of PSCs. The commonly adopted device structure of regular PSCs consists of indium tin oxide (ITO)/PEDOT:PSS (hole transport layer)/active layer/electron transport layer/low-work-function metal cathode (such as Ca and Al). It has been proved that the lifetime for regular PSCs is poor, because of the reactive metal cathode with a low-work function, which can be easily oxidized in air, and the hole-collecting interlayer of acidic and hygroscopic PEDOT:PSS etching of the ITO. As an alternative, there has been an increased interest in inverted PSCs (i-PSCs), in which the charge-collecting nature of the electrodes is reversed; that is, modified ITO is used as the cathode, and a high-work-function metal (such as Ag) is used as the anode. The i-PSCs have attracted more and more research because it provides not only long-term stability but also flexibility in the design and fabrication for advanced PSCs.For achi...

Photoacoustic imaging is a new noninvasive imaging technology that combines the advantages of optical imaging and ultrasound imaging. Using materials with good photoacoustic effects can improve imaging contrast and resolution. With the development of photoacoustic imaging in the field of medical treatment, research pertaining to photoacoustic functional materials is progressing continuously. In this study, we effectively synthesize a multifunctional photoacoustic and magnetocaloric nanomaterial, i.e., SiO 2 /C/Fe 3 O 4 via a onestep synthesis method. For theoretical analysis, the finite elemental analysis method is used to simulate the photoacoustic and magnetocaloric signals of the material. To obtain the experimental results, the SiO 2 /C/Fe 3 O 4 suspension is excited by a 532 nm nanosecond pulsed laser irradiation to obtain the photoacoustic signal of the material. The temperature increase of the material is measured under a 365 kHz alternating magnetic field. The results show that SiO 2 /C/Fe 3 O 4 exhibits good photoacoustic and magnetocaloric effects, rendering it feasible as a contrast agent for photoacoustic imaging and magnetocaloric therapy.

With excellent thermal conductivity and unique two-dimensional structure, the graphene heat dissipation film (GHDF) has been a potential photoacoustic (PA) material for multiple applications. In this study, we apply the GHDF into laser ultrasonic detection of seismic physical model (SPM). The PA effect of the GHDF is theoretically analyzed and experimentally demonstrated. The GHDF is physically attached to the upper surface of SPM, and excited effectively by a 532 nm pulsed laser. Distinguishable layered echo signal of SPM verifies the feasibility of the ultrasonic excitation approach using GHDF. This work opens up a new application of GHDF in ultrasonic detection of SPM.