CuInS2 Quantum Dots Research Articles

Enhanced electroluminescence from MEH-PPV-POSS:CuInS2 nanocomposite based organic light emitting diode

Polymer:quantum dot (QD) composites show enhanced optical and electronic properties. In this study, polymer light-emitting diodes (PLEDs) were fabricated and characterized using poly[2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylenevinylene] end capped with polyhedral oligomeric silsesquioxanes (MEH-PPV-POSS) as a luminescent polymer host and copper indium disulfide (CuInS2) QDs as a dopant. The emitted light originates from MEH-PPV-POSS. Incorporation of CuInS2 QDs into polymer matrix until certain amounts improved the device performance in terms of electroluminescence (EL) intensity, luminance, current and power efficiency compared to that of the undopped device. The improvement is remarkable when the QD concentration is 0.3wt% in the composite. We demonstrate that CuInS2 QDs provide a better balance of charge carriers and prevent the formation of polymeric aggregates.

CuInS2 quantum dots synthesized by a solvothermal route and their application as effective electron acceptors for hybrid solar cells

This paper describes a solvothermal approach to synthesize CuInS2 quantum dots (QDs) and demonstrates their application as a potential electron accepting material for polymer-based hybrid solar cells, for the first time. The CuInS2 QDs with a size of 2–4 nm are synthesized by the solvothermal method with 4-bromothiophenol (HSPh) as both reduction and capping agents, and characterized by XRD, XPS, TEM, FT-IR, cyclic voltammetry (CV), and absorption and photoluminescence spectra. Results reveal that the CuInS2 QDs result from the solvothermal decomposition of a soluble organic sodium salt as an intermediate precursor formed by simple reactions among CuCl2, InCl3, HSPh and Na2S at room temperature; they have an ionization potential (IP) of −5.8 eV and an electron affinity (EA) of −4.0 eV and can quench effectively the luminescence of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV). Due to the favorable IP and EA positions with respect to MEH-PPV, the CuInS2 QDs act as an effective electron acceptor for the hybrid solar cells based on MEH-PPV/CuInS2-QDs blends with a wide spectral response extending from 300 to 900 nm, by allowing the efficient charge separation for neutral excited states produced either on the polymer or on the QDs. The MEH-PPV/CuInS2-QDs solar cells exhibit a promising open circuit voltage (Voc) of 0.62 V under the monochromic illumination of 15.85 mW cm−2 at 470 nm. The charge transfer processes in the solar cells are also described.

Solution synthesis of high-quality CuInS2 quantum dots as sensitizers for TiO2 photoelectrodes

This study reports the solvothermal synthesis of colloidal CuInS2 quantum dots (QDs) for use as sensitizers for photoelectrochemical cells. The synthesis is conducted in an autoclave containing CuCl, InCl3, and S at a Cu/In/S ratio of 1/1/100. This high sulfur-excess environment leads to burst nucleation of CuInS2 at relatively low temperatures. For synthesis conducted at 110–150 °C for 1 h, the atomic ratio of the CuInS2 products is Cu : In : S = 1.1 : 1.0 : 2.1 and the particle size increases with the temperature from 3.5 to 4.3 nm, with a narrow size distribution within 7–11%. The as-prepared colloidal CuInS2 exhibits the quantum confinement effect in the optical absorption spectra. The photoluminescence emission of the resulting CuInS2 QDs has high energy, which may result from excited electrons falling from quantized levels to the ground states. Under illumination of simulated AM 1.5 G at one sun intensity, the CuInS2-sensitized TiO2 electrodes in aqueous sulfide/sulfite electrolyte show light-to-chemical energy conversion efficiencies of 1.9% at a +0.23 V bias and 1.2% at short-circuit. These encouraging conversion efficiencies are attributed to the high energy state of the photoexcited electrons in the CuInS2 QDs.

Colloidal Synthesis of Ternary Copper Indium Diselenide Quantum Dots and Their Optical Properties

Ternary direct semiconductor CuInSe2 quantum dots (QDs) with average particle sizes ranging from 1.2 to 5.6 nm have been synthesized by a colloidal route using commercially available materials. The size-dependent optical band gap and photoluminescence (PL) band shift due to the quantum size effect were successfully observed. The optical band gap evaluated from the optical absorption spectra was varied from 1.48 eV for the 5.6-nm QDs to 1.66 eV for the 1.2-nm QDs. In the PL spectra, the wavelength of the emission band varied from 918 to 838 nm corresponding to the crystal size variation from 5.6 to 1.2 nm. Because the PL band showed a large Stokes shift above 100 meV, the origin of the PL band was related to the electronic transition via defect levels. Based on the slightly In-rich composition of the QDs and the comparatively large increase in energy of the PL band with decreasing crystal size, the emission was suggested to be due to the recombination between electrons in the quantized conduction band and holes in the copper vacancy acceptor.

SEPARATED CuInSe2 QUANTUM DOTS ON ZnO THIN FILM BY ICP-ASSISTED MAGNETRON SPUTTERING

Uniformly hemispherical separated CuInSe 2 (CIS) quantum dots (QDs) were fabricated by low-frequency inductivity coupled plasma (LF-ICP) assisted radio-frequency (RF) magnetron sputtering technique from a ternary compound target on Si (100) and glass substrate with ZnO film serving as buffer layer. The average lateral size and densities of the QDs could be controlled by appropriate deposition parameters. The distribution scope of diameters was from 40 to 120 nm, density was from 4.5E9 to 2.1E11/cm2. Field-emission scanning electron microscope (FE-SEM) and energy-dispersive X-ray (EDX) spectrometer were adopted to measure the properties of CIS QDs.

Self-assembled large-scale and cylindrical CuInSe2 quantum dots on indium tinoxide films

CuInSe2 (CIS) quantum dots (QDs) have been prepared by radio-frequencyreactive magnetron sputtering from a ternary compound target on glass substratescoated with indium tin oxide at low temperatures. Uniformly distributed CIS QDswith a regular shape can be grown in this way. The average lateral size ofthe dots can be varied between 40 and 80 nm by making appropriatechoices of substrate temperature, power density, and total CIS coverage.

A Novel Route for the Preparation of CuSe and CuInSe2 Nanoparticles

CuInSe2 quantum dots are reported here for the first time. The highly crystalline nanoparticles of CuInSe2 and also of CuSe were prepared by reaction in tri-n-octylphosphine oxide (TOPO), producing TOPO-capped particles that are close to monodisperse. Transmission electron microscopy shows that the particles are spherical, with clear lattice fringes (see Figure).