Consequences of Anode Interfacial Layer Deletion. HCl-Treated ITO in P3HT:PCBM-Based Bulk-Heterojunction Organic Photovoltaic Devices
NORTHWESTERN UNIV EVANSTON IL MATERIALS RESEARCH CENTER
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In studies to simplify the fabrication of bulk-heterojunction organic photovoltaic OPV devices, it was found that when glasstin-doped indium oxide ITO substrates are treated with dilute aqueous HCl solutions, followed by UV-ozone UVO, and then used to fabricate devices of the structure glassITOP3HTPCBMLiFAl, device performance is greatly enhanced. Light-to-power conversion efficiency Eff increases from 2.4 for control devices in which the ITO surface is treated only with UVO, to 3.8 with the HCl UVO treatment - effectively matching the performance of an identical device having a PEDOTPSS anode interfacial layer. The enhancement originates from increases in VOC from 463 mV to 554 mV, and FF from 49 to 66. The modified-ITO device also exhibits a 4x enhancement in thermal stability versus an identical device containing a PEDOTPSS anode interfacial layer. To understand the origins of these effects, the ITO surface is analyzed as a function of treatment by ultraviolet photoelectron spectroscopy work function measurements, X-ray photoelectron spectroscopic composition analysis, and atomic force microscopic topography and conductivity imaging. Additionally, a diode-based device model is employed to further understand the effect of ITO surface treatment on device performance.
- Electrical and Electronic Equipment
- Electrooptical and Optoelectronic Devices
- Properties of Metals and Alloys
- Atomic and Molecular Physics and Spectroscopy