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<p>This study aims to demonstrate a quantum dot (QD) based heterojunction with working diode behaviour. This involves three steps, (1) fabrication of QD-sized tin sulphide (SnS) nanoparticles, (2) development of a compact TiO<sub>2</sub> layer, (3) fabrication of a heterojunction by a multi-layered structure. The colloidal synthesis process was used to prepare the SnS QDs. The size of the QDs was controlled by the addition of trioctylphosphine oxide (TOPO) to the synthesis process. HRTEM shows that the size of QDs is around 2&#xa0;nm which is much less than Excitonic Bohr’s radius of SnS (7&#xa0;nm). The crystalline peaks from (120) and (111) planes in the powder X-ray diffraction spectrum confirm the SnS material. A compact TiO<sub>2</sub> layer was prepared by hydrothermal method. XRD confirms the rutile phase of TiO<sub>2</sub>. SnS QDs were coated on it by the spray pyrolysis method. Parallel electrodes with silver paste were led on top of QD film to make the electrical contact. Dark I-V confirms Shockley diode-type behaviour. Sharp breakdown voltage is observed at 3.7&#xa0;V and very little leakage current is observed as a reverse saturation current, of the order of 10<sup>–4</sup>&#xa0;mA/cm<sup>2</sup>. These results confirm the formation of a proper rectifying contact. A model with double diode and shunt resistance is proposed to understand the I-V characteristics. From the modelling, it is seen that the heterojunction has two diodes, one with ideality factor 1, another diode with ideality factor more than 2, high shunt resistance and one non-linear component SCLC in series. This modelling will help to make good SnS QDs based heterojunction&#xa0;device.</p>

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Electrical characterization and double diode modelling of heterojunction of TiO2-SnS quantum dots

  • 期刊论文

  • 发表日期：

    2025年4月8日

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  • Subhashis Saha,
  • N. Sivakumar,
  • Narendra Bandaru,
  • Somnath Chanda Roy,
  • Jatindra Kumar Rath

摘要

This study aims to demonstrate a quantum dot (QD) based heterojunction with working diode behaviour. This involves three steps, (1) fabrication of QD-sized tin sulphide (SnS) nanoparticles, (2) development of a compact TiO2 layer, (3) fabrication of a heterojunction by a multi-layered structure. The colloidal synthesis process was used to prepare the SnS QDs. The size of the QDs was controlled by the addition of trioctylphosphine oxide (TOPO) to the synthesis process. HRTEM shows that the size of QDs is around 2 nm which is much less than Excitonic Bohr’s radius of SnS (7 nm). The crystalline peaks from (120) and (111) planes in the powder X-ray diffraction spectrum confirm the SnS material. A compact TiO2 layer was prepared by hydrothermal method. XRD confirms the rutile phase of TiO2. SnS QDs were coated on it by the spray pyrolysis method. Parallel electrodes with silver paste were led on top of QD film to make the electrical contact. Dark I-V confirms Shockley diode-type behaviour. Sharp breakdown voltage is observed at 3.7 V and very little leakage current is observed as a reverse saturation current, of the order of 10–4 mA/cm2. These results confirm the formation of a proper rectifying contact. A model with double diode and shunt resistance is proposed to understand the I-V characteristics. From the modelling, it is seen that the heterojunction has two diodes, one with ideality factor 1, another diode with ideality factor more than 2, high shunt resistance and one non-linear component SCLC in series. This modelling will help to make good SnS QDs based heterojunction device.