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Composite formation in CdSe:Cu₂Se nanocrystal films, charge transport characteristics and heterojunction performance.

ABSTRACT: The use of nanocrystals as materials for potential technological applications depends on tailoring their properties through intentional doping with external impurities. We have used a new technique to synthesize nanocrystal thin films of CdSe:Cu₂Se containing different weight percentages (wt%) of Cu₂Se. The films were deposited on glass substrates at room temperature by co-evaporation of CdSe and Cu₂Se powder in nitrogen gas at a pressure larger than that required for conventional thin film deposition. The films consisted of nanograins of CdSe doped with Cu₂Se (i.e., nanograins of Cd_1-x Cu_2(x)Se where x is the atom% of Cu₂Se doped into CdSe) for lower wt% of Cu₂Se, and nanocomposites of Cd_1-x Cu_2(x)Se and Cu₂Se for higher wt% of Cu₂Se. An energy band diagram built using the Anderson model was used for discussing the heterojunction characteristics of the junction between nanograins of Cd_1-x Cu_2(x)Se and Cu₂Se. To investigate the usefulness of the nanocrystal thin films of CdSe:Cu₂Se for practical applications, the I-V characteristics of p-p and p-n hetero-junctions formed by the films respectively with nanostructured films of similarly deposited Cu₂Se and CdSe films were studied.

SUBMITTER: Babu NS

PROVIDER: S-EPMC9050001 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Composite formation in CdSe:Cu2Se nanocrystal films, charge transport characteristics and heterojunction performance.

Babu N Sajid NS Khadar M Abdul MA

RSC advances 20200201 15

The use of nanocrystals as materials for potential technological applications depends on tailoring their properties through intentional doping with external impurities. We have used a new technique to synthesize nanocrystal thin films of CdSe:Cu2Se containing different weight percentages (wt%) of Cu2Se. The films were deposited on glass substrates at room temperature by co-evaporation of CdSe and Cu2Se powder in nitrogen gas at a pressure larger than that require ...[more]

PMID: 35496572

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Project description:A sequence of chemical vapor synthesis and thermal annealing in defined gas atmospheres was used to prepare phase-pure anatase TiO2 nanocrystal powders featuring clean surfaces and a narrow particle size distribution with a median particle diameter of 14.5 ± 0.5 nm. Random networks of these nanocrystals were immobilized from aqueous dispersions onto conducting substrates and are introduced as model systems for electronic conductivity studies. Thermal annealing of the immobilized films at 100 °C < T < 450 °C in air was performed to generate particle-particle contacts upon virtual preservation of the structural properties of the nanoparticle films. The distribution of electrochemically active electronic states as well as the dependence of the electronic conductivity on the Fermi level position in the semiconductor films was studied in aqueous electrolytes in situ using electrochemical methods. An exponential distribution of surface states is observed to remain unchanged upon sintering. However, capacitive peaks corresponding to deep electron traps in the nanoparticle films shift positive on the potential scale evidencing an increase of the trapping energy upon progressive thermal annealing. These peaks are attributed to trap states at particle-particle interfaces in the random nanocrystal network (i.e., at grain boundaries). In the potential region, where the capacitive peaks are detected, we observe an exponential conductivity variation by up to 5 orders of magnitude. The potential range featuring the exponential conductivity variation shifts positive by up to 0.15 V when increasing the sintering temperature from 100 to 450 °C. Importantly, all films approach a potential- and sintering-temperature-independent maximum conductivity of ∼10-4 Ω-1·cm-1 at more negative potentials. On the basis of these results we introduce a qualitative model, which highlights the detrimental impact of electron traps located on particle-particle interfaces on the electronic conductivity in random semiconductor nanoparticle networks.

Dataset Information

Composite formation in CdSe:Cu₂Se nanocrystal films, charge transport characteristics and heterojunction performance.

Publications

Composite formation in CdSe:Cu<sub>2</sub>Se nanocrystal films, charge transport characteristics and heterojunction performance.

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