17 September 2011 Charge-transfer excitons at semiconductor polymer heterojunctions in efficient organic photovoltaic diodes
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Proceedings Volume 8098, Physical Chemistry of Interfaces and Nanomaterials X; 80980L (2011); doi: 10.1117/12.894025
Event: SPIE NanoScience + Engineering, 2011, San Diego, California, United States
Abstract
In organic photovoltaic diodes, singlet intrachain excitons dissociate into geminate polaron pairs (GPP) at the heterojonction, which further dissociate into photocarriers or relax into charge transfer exciton (CTX) states. Our temperature-dependent, time-resolved spectroscopic approach unravels the dynamics of those species in films of polycarbazole/fullerene derivative blend. We find that GPP act as a dark reservoir that feeds the CTX. At low temperature, the GPP are trapped and feed the CTX via tunneling, but not the free photocarriers. At room temperature, some of the GPP can overcome the Coulomb barrier and feed the CTX promptly, or be deeply trapped and feed the CTX on several timescales. We find that at room temperature, 16% of the geminate recombination is accounted for by trapped geminate polaron pairs.
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Françoise Provencher, Maciej Sakowicz, Colin-Nadeau Brosseau, Richard Leonelli, Carlos Silva, "Charge-transfer excitons at semiconductor polymer heterojunctions in efficient organic photovoltaic diodes", Proc. SPIE 8098, Physical Chemistry of Interfaces and Nanomaterials X, 80980L (17 September 2011); doi: 10.1117/12.894025; http://dx.doi.org/10.1117/12.894025
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KEYWORDS
Excitons

Organic photovoltaics

Absorption

Polarons

Polymers

Diodes

Solar cells

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