Organic photodetectors (PDs) have been the subject of extensive research in the past decade due to several inherent advantages: large-area detection, wide selection of materials, and low-cost fabrication on flexible substrates. High external quantum efficiency (EQE) [1,2] , full-color [3,4] , fast-response [5,6] , and position-sensitive [7] PDs have been reported in the past.However, there are few reports on organic near-infrared photodetectors (NIR-PDs) in spite of their tremendous potential in industrial and scientific applications, such as remote control, chemical/biological sensing, optical communication, and spectroscopic and medical instruments.[8] S. Meskers and co-workers reported an infrared PD in which doped poly(2, 4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) was used as the active material.[9] More recently, G. Konstantatos and coworkers fabricated NIR-PDs by spin-coating colloidal quantum dots from solution onto gold interdigitated electrodes.[10] The device showed a large photoconductive gain and high detectivity at 1.3 lm. However, 3-dB bandwidth was only about 18 Hz and the working voltage was as high as 40 V. These characteristics strongly restrict their applications in the fields of imaging and communication where high-speed and low-power PDs are desired. Thus, there is a strong need for the development of fast response and low working voltage NIR-PDs while simultaneously maintaining the benefit of low-cost solution process.Here we report an organic near-infrared photodetector using a new low band gap polymer. By utilizing an ester group modified polythieno[3,4-b]thiophene, we have successfully lowered the highest occupied molecular orbital (HOMO) energy level of the low band gap (LBG) polymer, so that it can match the energy level of (6,6)-phenyl C 61 -butyric acid methyl ester (PCBM), and has good solubility and easy processing ability.In this communication, we report a device which has a donoracceptor type energy structure whose operation shows excellent NIR detection capability. Reports on LBG polymers for solar energy conversion have emerged recently. [11][12][13][14][15][16] The preparation of LBG, high mobility, solution-processable polymers is not trivial and requires judicious design.[16] Among several band gap tuning strategies for conjugated polymers, polymerization of fused heterocyclic rings has been known to yield polymers with very low band gaps. [17,18] Polythieno[3,4-b]thiophene (PTT) is one kind of LBG polymers in which the fused thiophene moieties can stabilize the quinoid structure of the backbone, thereby reducing the band gap of the conjugated system. [19,20] Several PTTs without side chains have been reported previously, but the poor solubility makes them difficult to process and limits their use in electro-optical and electronic devices. [21][22][23] Synthesis of alkyl chains substituted thieno [3,4-b]thiophenes monomers have been reported and the resulting polymers exhibit better solubility, but poor oxidative stability. [19] It was found that the HO...

crisis and environmental issue. [1] Electrochemical water electrolysis offers a promising and effective strategy to produce high-quality H 2 without carbon emission. [2] However, the sluggish kinetics of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has been a huge challenge for water splitting, which has spurred researchers for exploiting high-efficiency electrocatalysts with reduced dynamic overpotentials. [3] AlthoughPt-based materials and Ru/Ir-based oxides are still known as the most efficient catalysts for HER and OER, they suffer from low abundance and high prices, leading to difficulties in the largescale commercial application. [4] In addition, the most obtained electrocatalysts are not capable of possessing both excellent HER and OER performance in a same electrolyte due to incompatibility of activity over different pH ranges. [5] Therefore, constructing non-noble metal bifunctional electrocatalysts with high performance and cost-effectiveness has become a hot spot for efficient overall water splitting.Recently, low-cost nickel chalcogenides, such as NiS, NiS 2 , and Ni 3 S 2 , have attracted enormous attention for electrolytic water splitting. [6] In particular, the Ni 3 S 2 electrocatalyst has been widely researched due to high conductivity and unique structure configuration, while the imprisoned HER/OER activity Rational design and construction of bifunctional electrocatalysts with excellent activity and durability is imperative for water splitting. Herein, a novel topdown strategy to realize a hierarchical branched Mo-doped sulfide/phosphide heterostructure (Mo-Ni 3 S 2 /Ni x P y hollow nanorods), by partially phosphating Mo-Ni 3 S 2 /NF flower clusters, is proposed. Benefitting from the optimized electronic structure configuration, hierarchical branched hollow nanorod structure, and abundant heterogeneous interfaces, the as-obtained multisite Mo-Ni 3 S 2 /Ni x P y /NF electrode has remarkable stability and bifunctional electrocatalytic activity in the hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) in 1 m KOH solutions. It possesses an extremely low overpotential of 238 mV at the current density of 50 mA cm −2 for OER. Importantly, when assembled as anode and cathode simultaneously, it merely requires an ultralow cell voltage of 1.46 V to achieve the current density of 10 mA cm −2 , with excellent durability for over 72 h, outperforming most of the reported Ni-based bifunctional materials. Density functional theory results further confirm that the doped heterostructure can synergistically optimize Gibbs free energies of H and O-containing intermediates (OH*, O*, and OOH*) during HER and OER processes, thus accelerating the catalytic kinetics of electrochemical water splitting. This work demonstrates the importance of the rational combination of metal doping and interface engineering for advanced catalytic materials.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.

4,7-Di(thiophen-2-yl)benzothiadiazole (DTBT) has been used to construct a number of donor-acceptor low band gap polymers for bulk heterojunction (BHJ) photovoltaics with high efficiency numbers. Its strong tendency to π-stack often leads to polymers with low molecular weight and poor solubility, which could potentially be alleviated by anchoring solubilizing chains onto the DTBT unit. A systematic study of the effect of positioning alkyl chains on DTBT on properties of polymers was implemented by investigating a small library of structurally related polymers with identical conjugated backbone. This series of donoracceptor polymers employed a common donor unit, benzo[2,1-b:3,4-b 0 ]dithiophene (BDT), and modified DTBT as the acceptor unit. Three variations of modified DTBT units were prepared with alkyl side chains at (a) the 5and 6-positions of 2,1,3-benzothiadiazole (DTsolBT), (b) 3-positions of the flanking thienyl groups (3DTBT), and (c) 4-positions (4DTBT), in addition to the unmodified DTBT. Contrary to results from previous studies, optical and electrochemical studies disclosed almost identical band gap and energy levels between PBDT-4DTBT and PBDT-DTBT. These results indicated that anchoring solubilizing alkyl chains on the 4-positions of DTBT only introduced a minimum steric hindrance within BDT-DTBT, maintaining the extended conjugation of the fundamental structural unit (BDT-DTBT). More importantly, the additional high molecular weight and excellent solubility of PBDT-4DTBT led to a more uniform mixture with PCBM, with better control on the film morphology. All these features of PBDT-4DTBT led to a significantly improved efficiency of related BHJ solar cells (up to 2.2% has been observed), triple the efficiency obtained from BHJ devices fabricated from the "conventional" PBDT-DTBT (0.72%). Our discovery reinforced the importance of high molecular weight and good solubility of donor polymers for BHJ solar cells, in addition to a low band gap and a low HOMO energy level, in order to further enhance the device efficiencies.

In this contribution we have developed a useful and experimentally easy way to use C60 powder to directly fabricate C60 nanotubes with a mondisperse size distribution and uniform orientation. The structure of C60 nanotubes was confirmed by SEM, TEM, and FT-IR.