Low-temperature, solution-processed, layered V sub(2)O sub(5) hydrate as the hole-transport layer for stable organic solar cells

Layered V sub(2)O sub(5) hydrate has been applied as the hole transport layer (HTL) in organic solar cells (OSCs). V sub(2)O sub(5) is obtained from a sodium metavanadate solution in water under ambient conditions, resulting in a final thin film of formula V sub(2)O sub(5).0.5H sub(2)O. The 0.5 wate...

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Bibliographic Details
Published in:Energy & environmental science 2013-09, Vol.6 (10), p.3088-3098
Main Authors: Teran-Escobar, Gerardo, Pampel, Jonas, Caicedo, Jose M, Lira-Cantu, Monica
Format: Article
Language:English
Subjects:
Electrodes
Hydrates
Photovoltaic cells
Sodium
Solar cells
Thin films
Vanadium pentoxide
X-ray photoelectron spectroscopy
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Summary:Layered V sub(2)O sub(5) hydrate has been applied as the hole transport layer (HTL) in organic solar cells (OSCs). V sub(2)O sub(5) is obtained from a sodium metavanadate solution in water under ambient conditions, resulting in a final thin film of formula V sub(2)O sub(5).0.5H sub(2)O. The 0.5 water molecules are not removed from the V sub(2)O sub(5) layered structure unless the sample is heated above 250 degree C, which makes the thin film highly stable under real working conditions. The HTL was used in OSCs in the normal and the inverted configurations, applying metallic Ag as the back-metal electrode in both cases. Fabrication of both OSC configurations completely by solution-processing printing methods in air is possible, since the Al electrode needed for the normal-configuration OSC is not required. The work function (WF) and band gap energy (BG) of the V sub(2)O sub(5) thin films were assessed by XPS, UPS and optical analyses. Different WF values were observed for V sub(2)O sub(5) prepared from a fresh V sub(2)O sub(5)-isopropan ol (IPA) solution (5.15 eV) and that prepared from a 24 h-old solution (5.5 eV). This difference is due to the gradual reduction of vanadium (from V super(5+) to V super(4+)) in IPA. The OSCs made with the V sub(2)O sub(5) thin film obtained from the 24 h-old V sub(2)O sub(5)-IPA solution required photo-activation, whereas those made with the freshly obtained V sub(2)O sub(5) did not. Outdoor stability analyses of sealed OSCs containing a V sub(2)O sub(5) HTL in either configuration revealed high stability for both devices: the photovoltaic response at T sub(80) was retained for more than 1000 h.
ISSN:1754-5692
1754-5706
DOI:10.1039/c3ee42204f