Systematic Investigation of Organic Photovoltaic Cell Charge Injection/Performance Modulation by Dipolar Organosilane Interfacial Layers
NORTHWESTERN UNIV EVANSTON IL DEPT OF CHEMISTRY
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With the goal of investigating and enhancing anode performance in bulk-heterojunction BHJ organic photovoltaic OPV cells, the glasstin-doped indium oxide ITO anodes are modified with a series of robust silane-tethered bisfluoroarylamines to form self-assembled interfacial layers IFLs. The modified ITO anodes are characterized by contact angle measurements, X-ray reflectivity, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, atomic force microscopy, and cyclic voltammetry. These techniques reveal the presence of hydrophobic amorphous monolayers of 6.68 to 9.76 thickness, and modified anode work functions ranging from 4.66 to 5.27 eV. Two series of glassITOIFLactive layerLiFAl BHJ OPVs are fabricated with the active layer poly3-hexylthiophenephenyl- C71-butyric acid methyl ester P3HTPC71BM or poly4,8-bis2-ethylhexyl- oxybenzo1,2-b4,5-b dithiophene-2,6-diyl3-fluoro-2-2-ethylhexyl-carbonyl- thi-eno3,4-bthiophenediylphenyl-C71-butyric acid methyl ester PTB7PC71BM. OPV analysis under AM 1.5G conditions reveals significant performance enhancement versus unmodified glassITO anodes. Strong positive correlations between the electrochemically derived heterogeneous electron transport rate constants ks and the device open circuit voltage Voc, short circuit current Jsc, hence OPV power conversion efficiency PCE, are observed for these modified anodes. Furthermore, the strong functional dependence of the device response on ks increases as greater densities of charge carriers are generated in the BHJ OPV active layer, and is attributable to enhanced anode carrier extraction in the case of high-ks IFLs.
- Inorganic Chemistry
- Physical Chemistry