Growth of CuInS2 single crystals by THM

Hsu, Hungjen; Sun, Chuan; Hwang, H. L.

doi:10.1049/el:19840259

Cited by 5 publications

(3 citation statements)

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“…The electron mobility of 0.1 cm 2 V –1 s –1 is much lower than literature values, which range from 9 to 338 cm 2 V –1 s –1 . ,,,, Only in p-type CuInS 2 , made p-type by annealing in sulfur, a similarly low hole mobility of 0.1 cm 2 V –1 s –1 has been reported . Early on, nearly complete donor–acceptor self-compensation was speculated to cause electron localization, hence low mobility, with the residual donor defects being In Cu and V S .…”

Section: Discussionmentioning

confidence: 79%

“…The electrical resistivity at room temperature of 2.7 × 10 6 Ω·cm is high because of the low electron mobility and the low electron concentration of 2.3 × 10 13 cm –3 . High resistivities have been observed in as-grown crystals, ,, in crystals equilibrated with Zn (hence Cu-poor), and in thin films prepared without excess Cu. , As nanometer thick Cu-poor interphases cannot be detected by the routine XRD analysis typically employed in thin-film solar cell work, some of the highly resistive material of earlier studies also may have been stoichiometric CuInS 2 with interphase inclusions. With the reservation that the thermal activation energy of the electrical resistivity includes both electron density and mobility, the value measured here of 87 meV is compatible with the donor ionization energies identified in CuInS 2 , which range from 5 to 570 meV. ,− …”

Section: Discussionmentioning

confidence: 92%

“…To the device physics community, it is a given that the quantitative understanding of single-crystal chalcopyrite semiconductors is indispensable for reaching maximum thin-film solar cell performance. Therefore, soon after initial exploration, − raising solar cell efficiency became the principal motive for studying CuInS 2 single crystals. − An exemplary single-crystal result is the measurement of electron mobilities as high as 338 cm 2 /(V s), providing an important yardstick for assessing the device quality of polycrystalline CuInS 2 films. The goal of this study was to resolve a long-standing debate in polycrystalline CuInS 2 solar cells, namely the existence and presumed effects of Cu deficiency, by clearly identifying the phase(s) and defects in a CuInS 2 single crystal grown from a slightly copper-deficient melt.…”

Section: Introductionmentioning

confidence: 99%

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Observation of [V_Cu^1–In_i²⁺V_Cu^1–] Defect Triplets in Cu-Deficient CuInS₂

et al. 2020

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Copper indium disulfide (CuInS 2 ) is a semiconductor with a direct energy band gap of 1.53 eVan optimal value for highly efficient thin-film solar cells. But it has reached only ∼11% power conversion efficiency, far less than the theoretically achievable value of ∼30%. The cause of this low performance is not understood. A single crystal grown from 1 mol % Cu-deficient melt was studied by using atomic resolution high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) and electron dispersive spectroscopy (EDS). While the bulk crystal is exactly stoichiometric CuInS 2 , it contains nanometer thick, structurally coherent, Cu-deficient interphases that form along rotational twin boundaries in the {112} plane. Transition zones from the bulk crystal to the interphase are observed, where In is seen to move from its normal site In In in the chalcopyrite structure to a tetrahedral interstitial site In i , while Cu remains in its normal Cu Cu position. Two In In rows of the bulk crystal merge into one row of In i , causing excess In i in the interphase. The concentrations of Cu Cu and In i reflect a ratio of Cu vacancies, V Cu , to an excess In i of ∼2. Their relative lattice positions, and the high electrical resistivity of the crystal, suggest that V Cu and excess In i "precipitate" as self-compensating, electrically neutral, [V Cu 1− In i 2+ V Cu 1− ] defect triplets. This is the first atomic-level observation of the ordered defect that has been invoked as the basic structural modifier in chalcopyrite compound homologues. The interphases introduce an optical gap of 1.47 eV. Electron trapping in band tail states, evident from a photoconductivity exponent of 0.54, is the likely cause of an unusually low electron mobility of 0.1 cm 2 V −1 s −1 . The overall result is that making CuInS 2 slightly copper-poor inserts nanometer thick layers of the interphase into the bulk crystal. This study shows that apparently conflicting results of the effect of Cu deficiency on CuInS 2 thin-film solar cells may be resolved by analyzing structure and composition at nanometer spatial resolution.

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