TY - JOUR
T1 - 8.9% single-stack inverted polymer solar cells with electron-rich polymer nanolayer-modified inorganic electron-collecting buffer layers
AU - Woo, Sungho
AU - Hyun Kim, Wook
AU - Kim, Hwajeong
AU - Yi, Yeonjin
AU - Lyu, Hong Kun
AU - Kim, Youngkyoo
PY - 2014/5/13
Y1 - 2014/5/13
N2 - 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.
AB - 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.
KW - ZnO
KW - electron-rich polymers
KW - interfacial dipoles
KW - inverted polymer solar cells
KW - poly(ethyleneimine)
UR - http://www.scopus.com/inward/record.url?scp=84900495486&partnerID=8YFLogxK
U2 - 10.1002/aenm.201301692
DO - 10.1002/aenm.201301692
M3 - Article
AN - SCOPUS:84900495486
SN - 1614-6832
VL - 4
JO - Advanced Energy Materials
JF - Advanced Energy Materials
IS - 7
M1 - 1301692
ER -