High performance inverted polymer solar cells with solution processed metal oxides as electron transport layers: A comparative study

TitleHigh performance inverted polymer solar cells with solution processed metal oxides as electron transport layers: A comparative study
Publication TypeArticolo su Rivista peer-reviewed
Year of Publication2016
AuthorsMorvillo, P., Diana R., Nenna G., Bobeico E., Ricciardi Rosa, and Minarini Carla
JournalThin Solid Films
KeywordsAluminum, Aluminum-doped zinc oxide, butyric acid, Carboxylation, Carrier lifetime, Charge transfer, Charge transfer properties, Conversion efficiency, Efficiency, Electron transport layers, Electron transport properties, Impedance spectroscopy, Inverted polymer solar cells, Inverted solar cells, ITO glass, Optical films, Polymer Solar Cells, Polymers, Power conversion efficiencies, Solar cells, Spectroscopy, Temperature, Tin oxides, Titanium oxides, Zinc, Zinc oxide

Transparent metal oxides became an important class of low-temperature solution-processed electron transport layers (ETLs) for inverted polymer solar cells (PSCs) due to their high optical transparency in the visible range, relatively good electrical conductivity and tunable work function. In this work we made a comparative study between the electrical performances of devices realized with various metal oxides as ETLs: ZnO, ZnO:Al and TiOx. These oxides were prepared by low-temperature solution process techniques and used in PSCs with the configuration glass/Indium tin oxide (ITO)/ETL/photoactive layer/MoO3/Ag. The photoactive layer was a blend of poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] and [6,6]-phenyl C71 butyric acid methyl ester. The best power conversion efficiency (9.1%) under simulated AM1.5G illumination of 100 mW/cm2, was achieved for the PSC fabricated using a ZnO:Al interlayer. In order to elucidate the electrical processes at the interfaces between the ETL and the blend, impedance spectroscopy analysis was carried out. The ZnO:Al PSC shows better charge transfer properties between the active layer and the ITO and longer charge carrier lifetime. These factors contribute to improve the fill factor and increase the current output leading to an higher power conversion efficiency. © 2016 Elsevier B.V.


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