The effects of oxidation on lead sulfide quantum dots for photovoltaic devices = PbS 양자점 태양전지에서의 산화 효과 연구

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Colloidal quantum dots (CQDs) are of great interest in application of photovoltaic (PV) devices, due to their cost-effectiveness and solution-based processability. They also have excellent size-tunable optical properties which are highly desirable for optoelectronic devices. Lead(Ⅱ) sulfide (PbS) CQDs are promising material for PV devices due to their strong quantum confinement and high dielectric constant. However, the relatively low power-conversion-efficiency and poor air-stability are remaining challenges. It is essential to understand oxygen reaction on CQD PV devices for better performance. But only few reports have focused on the effects of oxidation. In this thesis, Schottky junction PVs comprised of PbS CQDs were fabricated. Uniform PbS CQDs (average diameter ~ 3 nm) were synthesized with thermal decomposition method. The PbS quantum dot (QD) films were produced via layer-by-layer spin-coating method using 1,2-ethanedithiol. Finally, we fabricated Schottky junction PVs by metal electrodes deposition. We employed a simple pre-oxidation treatment on PbS QD films prior to deposition of metal electrodes. It significantly enhanced an open-circuit voltage up to ~28%, fill factor up to ~ 72% and power conversion efficiency up to ~65%. Also it improved the capability of PCE retention in ambient condition. We systemically analyzed oxidation effects on PbS QD PVs with X-ray photoelectron spectroscopy (XPS), UV-visible spectrophotometer, transmission electron microscopy (TEM) analyses and current-voltage measurements. We found that the improvements of device characteristics are due to the formation of oxygen compounds: PbO, PbSO3 and PbSO4. The oxidation changed the characteristics of PbS QDs. Interestingly post-oxidation treatment also increased the device performance in case of no pre-oxidation. But it involved rapid degradation of device performance, while pre-oxidized devices showed gradual degradation. Pre-oxidation treatment improved not only device perf...
Jung, Yeon-Sikresearcher정연식
한국과학기술원 : 신소재공학과,
Issue Date
515094/325007  / 020113639

학위논문(석사) - 한국과학기술원 : 신소재공학과, 2013.2, [ viii, 63 p. ]


Lead sulfide; Colloidal quantum dots; Photovoltaic devices; 황화납; 콜로이드 양자점; 태양전지; 산화; Oxidation

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