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8.9% Single-Stack Inverted Polymer Solar Cells with Electron-Rich Polymer Nanolayer-Modified Inorganic Electron-Collecting Buffer Layers

Title
8.9% Single-Stack Inverted Polymer Solar Cells with Electron-Rich Polymer Nanolayer-Modified Inorganic Electron-Collecting Buffer Layers
Authors
Woo, S[Woo, Sungho]Kim, WH[Kim, Wook Hyun]Kim, H[Kim, Hwajeong]Yi, Y[Yi, Yeonjin]Lyu, HK[Lyu, Hong-Kun]Kim, Y[Kim, Youngkyoo]
DGIST Authors
Woo, S[Woo, Sungho]; Kim, WH[Kim, Wook Hyun]; Lyu, HK[Lyu, Hong-Kun]
Issue Date
2014-05
Citation
Advanced Energy Materials, 4(7)
Type
Article
Article Type
Article
Keywords
Buffer LayersConduction BandsConversion EfficiencyElectric ResistanceElectron-RichElectron-Rich PolymersHeterojunctionsInterfacial DipolesInverted Polymer Solar CellsOpen Circuit VoltageOptical WaveguidesPhotoelectronsPoly(Ethyleneimine)PolyethyleneimineSolar CellsSurface RoughnessUltraviolet Photoelectron SpectroscopyX Ray Photoelectron SpectroscopyZinc OxideZnO
ISSN
1614-6832
Abstract
Enhanced power conversion efficiency (PCE) is reported in inverted polymer solar cells when an electron-rich polymer nanolayer (poly(ethyleneimine) (PEI)) is placed on the surface of an electron-collecting buffer layer (ZnO). The active layer is made with bulk heterojunction films of poly[[4,8-bis[(2- ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl] [3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The thickness of the PEI nanolayer is controlled to be 2 nm to minimize its insulating effect, which is confirmed by X-ray photoelectron spectroscopy and optical absorption measurements. The Kelvin probe and ultraviolet photoelectron spectroscopy measurements demonstrate that the enhanced PCE by introducing the PEI nanolayer is attributed to the lowered conduction band energy of the ZnO layer via the formation of an interfacial dipole layer at the interfaces between the ZnO layer and the PEI nanolayer. The PEI nanolayer also improves the surface roughness of the ZnO layer so that the device series resistance can be noticeably decreased. As a result, all solar cell parameters including short circuit current density, open circuit voltage, fill factor, and shunt resistance are improved, leading to the PCE increase up to ≈8.9%, which is close to the best PCE reported using conjugated polymer electrolyte films. 8.9% power conversion efficiency is achieved using inverted-type polymer:fullerene solar cells. 2 nm-thick electron-rich poly(ethyleneimine) nanolayers are placed on the ZnO electron-collecting buffer layers and the increased built-in electric field caused by the lowered conduction band energy of ZnO layers enhances performance. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
URI
http://hdl.handle.net/20.500.11750/2656
DOI
10.1002/aenm.201301692
Publisher
Wiley-VCH Verlag
Files:
There are no files associated with this item.
Collection:
Convergence Research Center for Solar Energy1. Journal Articles
Division of IoT∙Robotics Convergence Research1. Journal Articles


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