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Modification of hybrid active bilayer for enhanced efficiency and stability in planar heterojunction colloidal quantum dot photovoltaics.

Heo SJ, Yoon S, Oh SH, Kim HJ - Nanoscale Res Lett (2013)

Bottom Line: Solution-processed planar heterojunction colloidal quantum dot photovoltaics with a hybrid active bilayer is demonstrated.A power conversion efficiency of 1.24% under simulated air mass 1.5 illumination conditions is reported.This was achieved through solid-state treatment with cetyltrimethylammonium bromide of PbS colloidal quantum dot solid films.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, South Korea. hjk3@yonsei.ac.kr.

ABSTRACT
Solution-processed planar heterojunction colloidal quantum dot photovoltaics with a hybrid active bilayer is demonstrated. A power conversion efficiency of 1.24% under simulated air mass 1.5 illumination conditions is reported. This was achieved through solid-state treatment with cetyltrimethylammonium bromide of PbS colloidal quantum dot solid films. That treatment was used to passivate Br atomic ligands as well as to engineer the interface within the hybrid active bilayer.

No MeSH data available.


XPS spectra of Pb 4f core levels to identify oxidized species. (a) CTAB-treated PbS CQDs film (0 day), (b) OA-treated PbS CQDs film (0 day), (c) CTAB-treated PbS CQDs film (3 days), and (d) OA-treated PbS CQDs film (3 days). The dark curve is the original data and the orange asterisk is the superposition of fitted peaks. Peaks are indicated for elemental lead (red squares), lead in PbS (orange circles), lead in PbS linked to capping ligands (green triangles), and lead in PbSOx (blue stars).
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Figure 5: XPS spectra of Pb 4f core levels to identify oxidized species. (a) CTAB-treated PbS CQDs film (0 day), (b) OA-treated PbS CQDs film (0 day), (c) CTAB-treated PbS CQDs film (3 days), and (d) OA-treated PbS CQDs film (3 days). The dark curve is the original data and the orange asterisk is the superposition of fitted peaks. Peaks are indicated for elemental lead (red squares), lead in PbS (orange circles), lead in PbS linked to capping ligands (green triangles), and lead in PbSOx (blue stars).

Mentions: XPS was carried out over 3 days to study the changes in chemical states in PbS CQD solid films. The measurements were taken with monochromated Al Κα radiation at 1,486.6 eV with a 0° emission angle. The binding energy scale was calibrated using the C1s spectral component at 284.8 eV. As can be seen in Figure 5, we focused on the Pb 4f core level to identify oxidized species. A Shirley-type background was used. Each species was fitted to a Pb 4f doublet with an area ratio of 4:3 and a splitting energy of 4.9 eV [16]. Oxidized species were present in all samples because all samples were exposed to ambient air after synthesis. Air exposure, which formed oxidized species, occurred rapidly (within a few minutes after initial exposure) and continued for months [17]. The amount of oxidized species increased from 18% to 33% over 3 days for OA-treated PbS CQD solid films, whereas the amount remained stable at 10% for CTAB-treated PbS CQD solid films. Surface oxidation of PbS CQDs was also inferred from a shift from OA-treated PbS CQD solid films (Figure 6) [18]. These findings supported the current density-voltage characteristics. The highly oxidized species were the main cause of decreased JSC and VOC in OA-treated cell; this is because PbSOx generates trap states below the conduction band [19].


Modification of hybrid active bilayer for enhanced efficiency and stability in planar heterojunction colloidal quantum dot photovoltaics.

Heo SJ, Yoon S, Oh SH, Kim HJ - Nanoscale Res Lett (2013)

XPS spectra of Pb 4f core levels to identify oxidized species. (a) CTAB-treated PbS CQDs film (0 day), (b) OA-treated PbS CQDs film (0 day), (c) CTAB-treated PbS CQDs film (3 days), and (d) OA-treated PbS CQDs film (3 days). The dark curve is the original data and the orange asterisk is the superposition of fitted peaks. Peaks are indicated for elemental lead (red squares), lead in PbS (orange circles), lead in PbS linked to capping ligands (green triangles), and lead in PbSOx (blue stars).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 5: XPS spectra of Pb 4f core levels to identify oxidized species. (a) CTAB-treated PbS CQDs film (0 day), (b) OA-treated PbS CQDs film (0 day), (c) CTAB-treated PbS CQDs film (3 days), and (d) OA-treated PbS CQDs film (3 days). The dark curve is the original data and the orange asterisk is the superposition of fitted peaks. Peaks are indicated for elemental lead (red squares), lead in PbS (orange circles), lead in PbS linked to capping ligands (green triangles), and lead in PbSOx (blue stars).
Mentions: XPS was carried out over 3 days to study the changes in chemical states in PbS CQD solid films. The measurements were taken with monochromated Al Κα radiation at 1,486.6 eV with a 0° emission angle. The binding energy scale was calibrated using the C1s spectral component at 284.8 eV. As can be seen in Figure 5, we focused on the Pb 4f core level to identify oxidized species. A Shirley-type background was used. Each species was fitted to a Pb 4f doublet with an area ratio of 4:3 and a splitting energy of 4.9 eV [16]. Oxidized species were present in all samples because all samples were exposed to ambient air after synthesis. Air exposure, which formed oxidized species, occurred rapidly (within a few minutes after initial exposure) and continued for months [17]. The amount of oxidized species increased from 18% to 33% over 3 days for OA-treated PbS CQD solid films, whereas the amount remained stable at 10% for CTAB-treated PbS CQD solid films. Surface oxidation of PbS CQDs was also inferred from a shift from OA-treated PbS CQD solid films (Figure 6) [18]. These findings supported the current density-voltage characteristics. The highly oxidized species were the main cause of decreased JSC and VOC in OA-treated cell; this is because PbSOx generates trap states below the conduction band [19].

Bottom Line: Solution-processed planar heterojunction colloidal quantum dot photovoltaics with a hybrid active bilayer is demonstrated.A power conversion efficiency of 1.24% under simulated air mass 1.5 illumination conditions is reported.This was achieved through solid-state treatment with cetyltrimethylammonium bromide of PbS colloidal quantum dot solid films.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, South Korea. hjk3@yonsei.ac.kr.

ABSTRACT
Solution-processed planar heterojunction colloidal quantum dot photovoltaics with a hybrid active bilayer is demonstrated. A power conversion efficiency of 1.24% under simulated air mass 1.5 illumination conditions is reported. This was achieved through solid-state treatment with cetyltrimethylammonium bromide of PbS colloidal quantum dot solid films. That treatment was used to passivate Br atomic ligands as well as to engineer the interface within the hybrid active bilayer.

No MeSH data available.