Abstract
We characterize and compare blended and bilayered heterojunctions of polymer photovoltaic devices using poly[oxa-1,4-phenylene-1,2-(1-cyano)- ethenylene-2,5-dioctyloxy-1,4-phenylene-1,2-(2-cyano)-ethenylene-1,4-phenylene] (CN-ether-PPV) and poly[2,5-dimethoxy-1,4-phenylene-1,2-ethenylene-2-methoxy-5- (2-ethylhexyloxy)-1,4-phenylene-1,2-ethenylene] (M3EH-PPV) as electron- and hole-transporting polymers, respectively. We find that both blended and bilayered structures have substantially improved current densities (>3mA/cm 2) and power efficiencies (∼1% under white light) over neat films. Improved exciton dissociation at multiple interfaces and reduced recombination due to energy and charge transfers increases the charge-carrier collection in both types of heterojunction devices, but low electron mobilities in the polymers lead to low fill factors and reduced quantum efficiency (∼20%) that limit the power efficiency. Time-resolved photoluminescence reveals that for blended structures both the hole and electron-transporting polymers undergo efficient quenching with the exciton decay being dominated by the existence of two fast decay channels of 0.12 and 0.78ns that are assigned to interspecies charge transfer and account for the increased short-circuit current observed. For layers, these components are not as prevalent. This result indicates that greater exciton generation at the dissociating interface and more efficient charge collection in the thin layers is primarily responsible for the improved short-circuit current, a conclusion that is further supported by numerical simulations of the exciton generation rate and charge collection. We also report evidence for an intermediate exciplex state in both types of structures with the greatest yield for blends with 50wt% of CN-ether-PPV. Overall, the improved performance is due to different processes in the two structures; efficient bulk exciton quenching and charge transfer in blends and enhanced exciton generation and charge collection in layers. The optimization of each photovoltaic heterostructured device relies on this understanding of the mechanisms by which each material architecture achieves high power efficiencies.
| Original language | English |
|---|---|
| Article number | 033709 |
| Journal | Journal of Applied Physics |
| Volume | 99 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Feb 1 2006 |
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ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)
- Physics and Astronomy(all)
Cite this
Comparison of blended versus layered structures for poly(p-phenylene vinylene)-based polymer photovoltaics. / Chasteen, S. V.; Härter, J. O.; Rumbles, Gary; Scott, J. C.; Nakazawa, Y.; Jones, M.; Hörhold, H. H.; Tillman, H.; Carter, S. A.
In: Journal of Applied Physics, Vol. 99, No. 3, 033709, 01.02.2006.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Comparison of blended versus layered structures for poly(p-phenylene vinylene)-based polymer photovoltaics
AU - Chasteen, S. V.
AU - Härter, J. O.
AU - Rumbles, Gary
AU - Scott, J. C.
AU - Nakazawa, Y.
AU - Jones, M.
AU - Hörhold, H. H.
AU - Tillman, H.
AU - Carter, S. A.
PY - 2006/2/1
Y1 - 2006/2/1
N2 - We characterize and compare blended and bilayered heterojunctions of polymer photovoltaic devices using poly[oxa-1,4-phenylene-1,2-(1-cyano)- ethenylene-2,5-dioctyloxy-1,4-phenylene-1,2-(2-cyano)-ethenylene-1,4-phenylene] (CN-ether-PPV) and poly[2,5-dimethoxy-1,4-phenylene-1,2-ethenylene-2-methoxy-5- (2-ethylhexyloxy)-1,4-phenylene-1,2-ethenylene] (M3EH-PPV) as electron- and hole-transporting polymers, respectively. We find that both blended and bilayered structures have substantially improved current densities (>3mA/cm 2) and power efficiencies (∼1% under white light) over neat films. Improved exciton dissociation at multiple interfaces and reduced recombination due to energy and charge transfers increases the charge-carrier collection in both types of heterojunction devices, but low electron mobilities in the polymers lead to low fill factors and reduced quantum efficiency (∼20%) that limit the power efficiency. Time-resolved photoluminescence reveals that for blended structures both the hole and electron-transporting polymers undergo efficient quenching with the exciton decay being dominated by the existence of two fast decay channels of 0.12 and 0.78ns that are assigned to interspecies charge transfer and account for the increased short-circuit current observed. For layers, these components are not as prevalent. This result indicates that greater exciton generation at the dissociating interface and more efficient charge collection in the thin layers is primarily responsible for the improved short-circuit current, a conclusion that is further supported by numerical simulations of the exciton generation rate and charge collection. We also report evidence for an intermediate exciplex state in both types of structures with the greatest yield for blends with 50wt% of CN-ether-PPV. Overall, the improved performance is due to different processes in the two structures; efficient bulk exciton quenching and charge transfer in blends and enhanced exciton generation and charge collection in layers. The optimization of each photovoltaic heterostructured device relies on this understanding of the mechanisms by which each material architecture achieves high power efficiencies.
AB - We characterize and compare blended and bilayered heterojunctions of polymer photovoltaic devices using poly[oxa-1,4-phenylene-1,2-(1-cyano)- ethenylene-2,5-dioctyloxy-1,4-phenylene-1,2-(2-cyano)-ethenylene-1,4-phenylene] (CN-ether-PPV) and poly[2,5-dimethoxy-1,4-phenylene-1,2-ethenylene-2-methoxy-5- (2-ethylhexyloxy)-1,4-phenylene-1,2-ethenylene] (M3EH-PPV) as electron- and hole-transporting polymers, respectively. We find that both blended and bilayered structures have substantially improved current densities (>3mA/cm 2) and power efficiencies (∼1% under white light) over neat films. Improved exciton dissociation at multiple interfaces and reduced recombination due to energy and charge transfers increases the charge-carrier collection in both types of heterojunction devices, but low electron mobilities in the polymers lead to low fill factors and reduced quantum efficiency (∼20%) that limit the power efficiency. Time-resolved photoluminescence reveals that for blended structures both the hole and electron-transporting polymers undergo efficient quenching with the exciton decay being dominated by the existence of two fast decay channels of 0.12 and 0.78ns that are assigned to interspecies charge transfer and account for the increased short-circuit current observed. For layers, these components are not as prevalent. This result indicates that greater exciton generation at the dissociating interface and more efficient charge collection in the thin layers is primarily responsible for the improved short-circuit current, a conclusion that is further supported by numerical simulations of the exciton generation rate and charge collection. We also report evidence for an intermediate exciplex state in both types of structures with the greatest yield for blends with 50wt% of CN-ether-PPV. Overall, the improved performance is due to different processes in the two structures; efficient bulk exciton quenching and charge transfer in blends and enhanced exciton generation and charge collection in layers. The optimization of each photovoltaic heterostructured device relies on this understanding of the mechanisms by which each material architecture achieves high power efficiencies.
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U2 - 10.1063/1.2168046
DO - 10.1063/1.2168046
M3 - Article
VL - 99
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 3
M1 - 033709
ER -