|Title||Elucidating the origin of the improved current output in inverted polymer solar cells|
|Publication Type||Articolo su Rivista peer-reviewed|
|Year of Publication||2016|
|Authors||Morvillo, P., Ricciardi Rosa, Nenna G., Bobeico E., Diana R., and Minarini Carla|
|Journal||Solar Energy Materials and Solar Cells|
|Keywords||butyric acid, Charge collection, Density of interface state, Impedance spectroscopy, Interface states, Inverted architectures, Inverted devices, Inverted polymer solar cells, Optical modeling, Photovoltaic performance, Polymer Solar Cells, Polymers, Solar cells, Solar power generation, Spectroscopy|
In this work, we compared the photovoltaic performance of standard and inverted polymer solar cells with the aim to elucidate the origin of the different current output. We realized devices with both architectures using a blend film of poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b:4,5-b′]dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiopene)-2,6-diyl] /[6,6]-phenyl C71 butyric acid methyl ester (PBDTTT-C:PCBM). The standard cell sequence is ITO/PEDOT:PSS/PBDTTT-C:PCBM/Ca/Al and the inverted one is ITO/ZnO/PBDTTT-C:PCBM/MoO3/Ag. The inverted architecture shows better performances compared to the standard one mainly in terms of current output. The optical modeling has revealed that this architecture allows more photons to be absorbed in the blend film, giving rise to an higher current output, although the observed improvement cannot be completely attributed to the calculated higher absorption of the incoming light. By using the impedance spectroscopy analysis, we found that the inverted device architecture has higher values for the interface trap time constant and the density of interface states. Both parameters contribute to retain the charge collection efficient, compared to the standard configuration, despite the increased charge carrier density and to further improve the current output. © 2016 Elsevier B.V. All rights reserved.
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