Query: N-Type conducting Cd Se nanocrystal solids,

Candidate papers:

abstract: A bottleneck limiting the widespread application of semiconductor nanocrystal solids is their poor conductivity. We report that the conductivity of thin films of n type CdSe nanocrystals increases by many orders of magnitude as the occupation of the first two electronic shells, 1Se and 1Pe, increases, either by potassium or electrochemical doping. Around half filling of the 1Se shell, a peak in the conductivity is observed, indicating shell to shell transport. Introducing conjugated ligands between nanocrystals increases the conductivities of these states to ~10 2 siemens per centimeter.
author_names: Dong Yu

Congjun Wang

Philippe Guyot-Sionnest
title: n Type Conducting CdSe Nanocrystal Solids
venue: Science
year: 2003

abstract: We present a general synthesis for a family of n type transparent conducting oxide nanocrystals through doping with aliovalent cations. These monodisperse nanocrystals exhibit localized surface plasmon resonances tunable in the mid and near infrared with increasing dopant concentration. We employ a battery of electrical measurements to demonstrate that the plasmonic resonance in isolated particles is consistent with the electronic properties of oxide nanocrystal thin films. Hall and Seebeck measurements show that the particles form degenerately doped n type solids with free electron concentrations in the range of 1019 to 1021 cm 3. These heavily doped oxide nanocrystals are used as the building blocks of conductive, n type thin films with high visible light transparency.
author_names: Benjamin T Diroll

Thomas R Gordon

E Ashley Gaulding

D R Klein

Taejong Paik

Hyeong Jin Yun

E D Goodwin

Divij Damodhar

Cherie R Kagan

Christopher B Murray
title: Synthesis of N Type Plasmonic Oxide Nanocrystals and the Optical and Electrical Characterization of their Transparent Conducting Films
year: 2014

abstract: Thermoelectric materials, capable of converting heat directly into electricity without moving parts, provide a promising solid state solution for waste heat harvesting. However, currently available commercial thermoelectric materials PbTe and Bi2Te3 are based on tellurium, an extremely scarce and expensive element, which prohibits large scale applications. Herein, we present a systematic study on a new low cost Te free material, n type Se doped Mg3Sb1.5Bi0.5, by combining the structure and property characterization with electronic structure and electrical transport modeling. Compared with pure Mg3Sb2, Se doped Mg3Sb1.5Bi0.5 shows the considerably enhanced power factor as well as much lower thermal conductivity. The excellent electrical transport originates from a nontrivial near edge conduction band with six conducting carrier pockets and a light conductivity effective mass as well as the weak contribution from a secondary conduction band with a valley degeneracy of 2. The accurate location of the conduct.
author_names: Jiawei Zhang

Lirong Song

Aref H Mamakhel

Mads Ry Vogel Jorgensen

Bo Brummerstedt Iversen
title: High Performance Low Cost n Type Se Doped Mg3Sb2 Based Zintl Compounds for Thermoelectric Application
year: 2017

abstract: We investigate the effects of stoichiometric imbalance on the electronic properties of lead chalcogenide nanocrystal films by introducing excess lead (Pb) or selenium (Se) through thermal evaporation. Hall effect and capacitance voltage measurements show that the carrier type, concentration, and Fermi level in nanocrystal solids may be precisely controlled through their stoichiometry. By manipulating only the stoichiometry of the nanocrystal solids, we engineer the characteristics of electronic and optoelectronic devices. Lead chalcogenide nanocrystal field effect transistors (FETs) are fabricated at room temperature to form ambipolar, unipolar n type, and unipolar p type semiconducting channels as prepared and with excess Pb and Se, respectively. Introducing excess Pb forms nanocrystal FETs with electron mobilities of 10 cm(2)(V s) which is an order of magnitude higher than previously reported in lead chalcogenide nanocrystal devices. Adding excess Se to semiconductor nanocrystal solids in PbSe Schottky solar cells enhances the power conversion efficiency.
author_names: Soong Ju Oh

Nathaniel E Berry

Ji-Hyuk Choi

E Ashley Gaulding

Taejong Paik

Sung-Hoon Hong

Christopher B Murray

Cherie R Kagan
title: Stoichiometric control of lead chalcogenide nanocrystal solids to enhance their electronic and optoelectronic device performance.
venue: ACS nano
year: 2013

abstract: line n Type CdS CdSe Electrodes," J. Electrochem. Soc. vol. 125 (1978) pp. 375 379. A. J. Strauss et al. "Phase Diagram of the CdTe CdSe Pseudo Binary System," J. Electrochem. Soc, vol. 117, (1970) pp. 1420 1426. H. Tai et al. "Optical Properties of (CdTe)(CdSe) and (CdTe) (CdS) Systems, Phys. Stat. Sol. (a) vol. 30, K115 K119 (1975) Berishvili et al. Poloprovodn Tekh Mikroelecktron, vol. 28, pp. 23 31 (1978) A. D. Stuckes, "Electrical Thermal Properties of Alloys of CdTe and CdSe," J. Phys. Chem. Solids, vol. 25, pp. 477 482 (1964) Chem. Abstracts, vol. 77, 157719d (1972) Chem. Abstracts, vol. 87 110018r (1977)
author_names: Alloy Photovoltaic

Mater Als

Gary Hodes

David Cahen
title: United States Patent 19 Hodes et al 54 CD SE TE ALLOY PHOTOVOLTAIC
year: 2017

abstract: The temperature and electrical field dependent conductivity of n type CdSe nanocrystal thin films is investigated. In the low electrical field regime, the conductivity follows sigma approximately exp( (T(/T)(1/2) in the temperature range 10<T<120 K. At high electrical field, the conductivity is strongly field dependent. At 4 K, the conductance increases by 8 orders of magnitude over one decade of bias. At a very high field, conductivity is temperature independent with sigma approximately exp( (E(/E)(1/2) The complete behavior is very well described by variable range hopping with a Coulomb gap.
author_names: Dong Yu

Congjun Wang

Brian L Wehrenberg

Philippe Guyot-Sionnest
title: Variable range hopping conduction in semiconductor nanocrystal solids.
venue: Physical review letters
year: 2004

abstract: Colloidal semiconductor nanocrystals have emerged as fascinating new materials and gained interest in the last 30 years because of their size, shape, and compositionally tunable electronic and optical properties as well as their potential to serve as artificial atoms. Challenges and opportunities have arisen when assembling nanocrystals into nanocrystal solids for electronic and optoelectronic applications, largely because of the significant influence of nanocrystal surface chemistry on the electronic, optical, and structural properties of nanocrystal solids. In order to assemble nanocrystal solids for high performance devices, we must understand and be able to control the effects of nanocrystal surface organic capping ligands, non stoichiometry, and impurity doping on the electronic and optoelectronic properties of the nanocrystal solids. Here, we show that exposing CdSe nanocrystals to methanol removes oleic acid capping ligands and/or Cd ions from the nanocrystal surface, introducing mid band gap trap states that are recombination centers for photogenerated electron/hole pairs. Using photoluminescence spectroscopy and photoconductivity measurements we illustrate that these trap states have the adverse effects of decreased photoluminescence quantum yield and lifetime and decreased photoconductivity. Treatment with CdCl2 fills these traps states, realizing a significant increase in photocurrent magnitude and lifetime. We present examples of intentional nanocrystal surface chemical modifications: non stoichiometry doping of PbSe nanocrystals by surface enrichment with excess Pb or Se, and surface impurity doping and passivation of CdSe nanocrystals by thermal diffusion of indium. We demonstrate how these modifications shift the Fermi level of the PbSe or CdSe nanocrystal solid through the density of electronic states of the valence band (PbSe nanocrystal solid only) mid gap, and the conduction band. Using field effect transistor and flash photolysis time resolved microwave conductivity measurements we show that control of the Fermi level can be used to effectively tailor the charge carrier polarity (PbSe nanocrystal solid only) mobility, and lifetime. We find that Se rich PbSe and non indium treated CdSe nanocrystals have a greater tendency to fuse with nearest neighbor nanocrystals than do Pb rich PbSe and indium treated CdSe nanocrystals. Finally, we present a flexible, robust method for assembling nanocrystals into high quality, ordered (in some cases superlattices) uniform nanocrystal solids for application in electronic and optoelectronic devices. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Chemistry First Advisor Cherie R. Kagan This dissertation is available at ScholarlyCommons: http:/repository.upenn.edu/edissertations/1744 Second Advisor Christopher B. Murray
author_names: E D Goodwin
title: The optoelectronic properties of surface modified semiconductor nanocrystal solids
year: 2015

abstract: Abstract Herein, we introduce a unique nanomaterial chemical transformation (NCT) process whereby selenium (Se) anion is introduced to colloidal silver (Ag) nanocrystals (NCs) to create nanostructured silver selenide (Ag2Se) We present a complete suite of material characterizations, including chemical, structural, optical, and electrical characterizations to understand the details of the transformation process. The Ag2Se thin films obtained through the NCT process exhibit degenerately doped n type semiconductor characteristics with high carrier mobility. We discuss the chemical mechanism that drives the material transformation and elucidates the origin of doping in these semiconducting thin films. We also demonstrate the robustness of Ag2Se thin films toward mechanical strain and temperature cycling stress for flexible device applications. We believed that the NCT process demonstrated here is of wide applicability to other material systems which can open up new avenues for solid state chemistry and device engineering research.
author_names: Sanghyun Jeon

Junhyuk Ahn

Junsung Bang

Ho Kun Woo

Shihab Bin Hafiz

Dong-Kyun Ko

Soong Ju Oh
title: Property engineering through nanomaterial chemical transformation of colloidal nanocrystal thin films
year: 2020

abstract: CdSe is an important compound semiconducting material for the development of various applications in solid state devices such as solar cells, high efficiency thin film transistors. In recent years major attention has been given to the investigation of structural and electrical properties for the improvement of performance of such devices and its applications[1] We prepared n type CdSe thin films on glass substrate using cadmium selenide material with various composition of Cd (99.999% and Se (99.999% by electron beam evaporation technique under vacuum 10 5 torr in vacuum coating unit, keep substrates at room temperature and studied the effect of composition ratio of cadmium selenium on thin films and evaluate the grain size, resistivity, hallmobility and carrier concentration in n type CdSe thin films.
author_names: A K Verma

S R Vishwakarma

R S N Tripathi
title: Effect of deposition parameter on structural and electrical properties of n type cadmium selenide thin films
year: 2011

abstract: In the present investigation, polycrystalline semiconductor Cd Se Te films have been electrodeposited at room temperature on conducting glass substrates using cyclic voltammetric technique under controlled periodic scans. The successive anodic and cathodic scans were recorded within the potential range, from 0 to 1.0 V, and over the range of periodic cycles, from 250 to 2,000, in an acidic bath containing respective reducible precursor ions like Cd2+ Se4+ Te4+ and 1 vol. Triton X 100 as the surface active reagent. Thin composite films were produced having variable thickness and composition and grain size of the order of 80 100 nm. The film properties were determined by focused ion beam analysis, energy dispersive analysis of x rays, x ray diffraction studies, atomic force microscopy, and scanning electron microscopy. Thickness of the semiconductor films was found to increase linearly with the number of voltammetric cycles. Band gap energies of the films as derived from the reflectance spectra were found to lie between 1.4 and 1.7 eV. The composite films of the Cd Se Te ternary system when electrochemically characterized in aqueous polysulfide solution exhibited n type semiconducting properties and photoconversion efficiency more than 0.4%
author_names: Chinmoy Bhattacharya

Jayati Datta
title: Synthesis of nanostructured Cd Se Te films through periodic voltammetry for photoelectrochemical applications
year: 2006