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Issue 28, 2011
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Enhanced photoelectric-conversion yield in niobium-incorporated In2S3 with intermediate band

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Abstract

β-In2S3 is a nontoxic window layer material usually used in a thin-film solar cell. Transition metal (TM)-incorporated In2S3 has been proposed to promote conversion efficiency in In2S3 because multi-photon absorption by an intermediate band (IB) would happen in the sulfide. In this paper, band-edge and photoelectric-conversion properties of Nb-substituted In2S3 have been probed by thermoreflectance (TR), photoconductivity (PC), and photo–voltage–current (Photo VI) measurements. The crystals of niobium-incorporated In2S3 with different Nb contents of In1.99S3:Nb0.01, In1.995S3:Nb0.005, and undoped In2S3 were grown by chemical vapor transport (CVT) method using ICl3 as a transport agent. X-ray diffraction measurements showed that the as-grown In2S3:Nb compounds are β-phase crystals with tetragonal structure. Lattice constants of the β-In2S3:Nb show shrinkage with the increase of the Nb content in the In2S3. Experimental TR spectra reveal four transition features including direct gap (E0), valence band to donor (EVS), valence band to IB (EIB), and acceptor to IB [Ed(IB)] transitions detected in the Nb-substituted In2S3 compounds. The band gap (E0) shows a reduction and the crystal color changes from fresh red, to red, to dark red with increasing Nb content in the undoped β-In2S3, β-In1.995S3:Nb0.005, and β-In1.99S3:Nb0.01. The PC and Photo VI measurements verified that high photoelectric-conversion efficiency occurred in the β-In2S3 with higher niobium content. The intermediate band (IB) was formed by Nb substitution with indium in the β-In2S3 [i.e. detected by EIB≈1.52 eV and Ed(IB) ≈ 1.42 eV]. The IB state should mainly dominate the multi-photon absorption capacity and enhance the photoelectric-conversion yield in the indium sulfide.

Graphical abstract: Enhanced photoelectric-conversion yield in niobium-incorporated In2S3 with intermediate band

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Publication details

The article was received on 18 Feb 2011, accepted on 04 May 2011 and first published on 13 Jun 2011


Article type: Paper
DOI: 10.1039/C1JM10731C
Citation: J. Mater. Chem., 2011,21, 10518-10524
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    Enhanced photoelectric-conversion yield in niobium-incorporated In2S3 with intermediate band

    C. Ho, J. Mater. Chem., 2011, 21, 10518
    DOI: 10.1039/C1JM10731C

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