title: Effect of Diels-Alder Reaction in C60-Tetracene Photovoltaic Devices.
abstract: Developing organic photovoltaic materials systems requires a detailed understanding of the heterojunction interface, as it is the foundation for photovoltaic device performance. The bilayer fullerene/acene system is one of the most studied models for testing our understanding of this interface. We demonstrate that the fullerene and acene molecules chemically react at the heterojunction interface, creating a partial monolayer of a Diels-Alder cycloadduct species. Furthermore, we show that the reaction occurs during standard deposition conditions and that thermal annealing increases the concentration of the cycloadduct. The cycloaddition reaction reduces the number of sites available at the interface for charge transfer exciton recombination and decreases the charge transfer state reorganization energy, increasing the open circuit voltage. The submonolayer quantity of the cycloadduct renders it difficult to identify with conventional characterization techniques; we use atom probe tomography to overcome this limitation while also measuring the spatial distribution of each chemical species.
authors: Department of Physics, ‡Materials Science Program, and §Department of Metallurgy and Materials Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.
authors: Andrew P
authors: AP
authors: Proudian
authors: Department of Physics, ‡Materials Science Program, and §Department of Metallurgy and Materials Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.
authors: Matthew B
authors: MB
authors: Jaskot
authors: Department of Physics, ‡Materials Science Program, and §Department of Metallurgy and Materials Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.
authors: Christelle
authors: C
authors: Lyiza
authors: Department of Physics, ‡Materials Science Program, and §Department of Metallurgy and Materials Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.
authors: David R
authors: DR
authors: Diercks
authors: Department of Physics, ‡Materials Science Program, and §Department of Metallurgy and Materials Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.
authors: Brian P
authors: BP
authors: Gorman
authors: Department of Physics, ‡Materials Science Program, and §Department of Metallurgy and Materials Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.
authors: Jeramy D
authors: JD
authors: Zimmerman
keywords: Acenes; atom probe tomography; cycloaddition; donor/acceptor interface; fullerenes; organic photovoltaics