电化学扫描隧道显微术:以Cu在Au(111)表面初始阶段电沉积为例

电化学扫描隧道显微术能在电解质溶液中获得随电位变化的电极表面高空间分辨率的结构信息及跟踪某些反应过程,为从高空间分辨率的角度理解界面结构和电极过程提供了一种强有力的手段。本文以电化学扫描隧道显微术研究Cu在Au(111)上电沉积初始阶段过程为例,与读者交流电化学扫描隧道显微术实验方面的经验,涉及实验装置、实验操作、实验步骤和注意事项等。

ELECTROCHEMICAL COPOLYMERIZATION OF ANILINE AND AZURE B

The electrochemical copolymerization of aniline and N,N,N'-trimethylthionin (azure B) in aqueous solutions has been carried out using the potential sweep method. The optimum conditions for the coelectrodeposition are that the pH value and the temperature of the electrolytic solution are controlled at 5.57 and 30 degreesC, respectively, and the scan potential range is set between -0.25 and 1.10 V (versus SCE). The copolymerization rate of aniline and azure B is about 3 times larger than that of aniline in the absence of azure B. The copolymerization of aniline and azure B was verified from the results of visible spectra during electrolysis, FTIR spectra and the atomic force microscopy (AFM) images of the polymers. The in situ visible spectrum for the electrolysis of the solution containing aniline and azure B is different from that of the respective aniline and azure B. The FTIR spectrum of the copolymer is not a superposition of that of polyaniline and poly(azure B). The AFM image of the copolymer is different from those of polyaniline and poly(azure B) and is not a mixture of individual polymers. The conductivity of the copolymer synthesized at pH 5.57 is four orders of magnitude higher than that of polyaniline synthesized under the same conditions, but in the absence of azure B. The electrochemical properties of the copolymer are mainly attributed to polyaniline, but the copolymer has a better electrochemical reversibility and a much faster charge transfer than those of polyaniline.

Efficient plasmon-enhanced perovskite solar cells by molecularly isolated gold nanorods

Perovskite solar cells(PSCs)are becoming a promising candidate for next-generation photovoltaic cells due to their attractive power conversion efficiency(PCE).Plasmonic enhancement is regarded as an optical tuning approach for further improving the PCE of single-junction PSCs toward Shockley-Queisser limit.Herein,we introduce molecularly isolated gold nanorods(Au NRs),bearing relatively stronger scattering ability and localized surface plasmonic resonance(LSPR)effect,in the rear side of perovskites in PSCs,for promoting light harvesting and for electrical enhancement.Owing to the larger refractive index and better matched energy level alignment,the 4-mercaptobenzoic acid molecules coated on Au NRs prove to play important dual roles:isolating the metallic Au NRs from contacting with perovskite,and facilitating more efficient charge separation and transport across the interface under the synergetic LSPR effect of Au NRs.Our work highlights the capability of the plasmonic approach by nanorods and by molecular isolation,extending nanoparticle-based plasmonic approaches,toward highly efficient plasmon-enhanced PSCs.

Intermolecular coupling enhanced thermopower in single-molecule diketopyrrolopyrrole junctions

Sorting out organic molecules with high thermopower is essential for understanding molecular thermoelectrics.The intermolecular coupling offers a unique chance to enhance the thermopower by tuning the bandgap structure of molecular devices,but the investigation of intermolecular coupling in bulk materials remains challenging.Herein,we investigated the thermopower of diketopyrrolopyrrole(DPP)cored single-molecule junctions with different coupling strengths by varying the packing density of the self-assembled monolayers(SAM)using a customized scanning tunneling microscope break junction(STM-BJ)technique.We found that the thermopower of DPP molecules could be enhanced up to one order of magnitude with increasing packing density,suggesting that the thermopower increases with larger neighboring intermolecular interactions.The combined density functional theory(DFT)calculations revealed that the closely-packed configuration brings stronger intermolecular coupling and then reduces the highest occupied molecular orbital(HOMO)-lowest unoccupied molecular orbital(LUMO)gap,leading to an enhanced thermopower.Our findings offer a new strategy for developing organic thermoelectric devices with high thermopower.

Quantification of electron accumulation at grain boundaries in perovskite polycrystalline films by correlative infrared-spectroscopic nanoimaging and Kelvin probe force microscopy

Organic–inorganic halide perovskites are emerging materials for photovoltaic applications with certified power conversion efficiencies(PCEs)over 25%.Generally,the microstructures of the perovskite materials are critical to the performances of PCEs.However,the role of the nanometer-sized grain boundaries(GBs)that universally existing in polycrystalline perovskite films could be benign or detrimental to solar cell performance,still remains controversial.Thus,nanometer-resolved quantification of charge carrier distribution to elucidate the role of GBs is highly desirable.Here,we employ correlative infrared-spectroscopic nanoimaging by the scattering-type scanning near-field optical microscopy with 20 nm spatial resolution and Kelvin probe force microscopy to quantify the density of electrons accumulated at the GBs in perovskite polycrystalline thin films.It is found that the electron accumulations are enhanced at the GBs and the electron density is increased from 6×10^(19) cm^(−3 )in the dark to 8×10^(19) cm^(−3 ) under 10 min illumination with 532 nm light.Our results reveal that the electron accumulations are enhanced at the GBs especially under light illumination,featuring downward band bending toward the GBs,which would assist in electron-hole separation and thus be benign to the solar cell performance.

Copper/cuprous sulfide electrode: preparation and performance

Cuprous sulfide(Cu2S) is a direct band-gap p-type semiconductor with excellent ionic/electronic hybrid conductivity. Although Cu/Cu2S/sulfide or polysulfide system is adopted as counter electrode of quantum-dots-sensitized solar cells(QDSSC), the electrode process is seldom reported. Here, the electrochemical growth of Cu2 S film on a copper(Cu) surface, the redox behaviors of sulfide and polysulfide, and the all-in-solid charge-transfer properties of Cu2 S film are investigated. It is clarified that the copper electrode simultaneously undergoes an activated process, a membrane growth process, and a redox phase transformation process. The solid charge-transfer capability of Cu2 S is quantified with a high exchange-current density of 2.27 A/cm2, which elucidates that the Cu/Cu2 S electrode is a qualified material for counter electrodes of QDSSC. These results aid understanding of the physicochemical mechanism of QDSSC with a polysulfide electrolyte and Cu/Cu2 S counter electrode.