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Role of Intrinsic Photogeneration in Single Layer and Bilayer Solar Cells with C60 and PCBM

Title data

Hahn, Tobias ; Tscheuschner, Steffen ; Saller, Christina ; Strohriegl, Peter ; Boregowda, Puttarraju ; Mukhopadhyay, Tushita ; Patil, Satish ; Neher, Dieter ; Bässler, Heinz ; Köhler, Anna:
Role of Intrinsic Photogeneration in Single Layer and Bilayer Solar Cells with C60 and PCBM.
In: The Journal of Physical Chemistry C. Vol. 120 (2016) Issue 43 . - pp. 25083-25091.
ISSN 1932-7455
DOI: https://doi.org/10.1021/acs.jpcc.6b08471

Abstract in another language

In an endeavor to examine how optical excitation of C60 and PCBM contribute to the photogeneration of charge carriers in organic solar cells, we investigated stationary photogeneration in single-layer C60 and PCBM films over a broad spectrum as a function of the electric field. We find that intrinsic photogeneration starts at a photon energy of about 2.25 eV, i.e., about 0.4 eV above the first singlet excited state. It originates from charge transfer type states that can autoionize before relaxing to the lower-energy singlet S1 state, in the spirit of Onsager’s 1938 theory. We analyze the internal quantum efficiency as a function of electric field and photon energy to determine (1) the Coulombic binding and separation of the electron–hole pairs, (2) the value of the electrical gap, and (3) which fraction of photoexcitations can fully separate at a given photon energy. The latter depends on the coupling between the photogenerated charge transfer states and the eventual charge transporting states. It is by a factor of 3 lower in PCBM. Close to the threshold energy for intrinsic photoconduction (2.25 eV), the generating entity is a photogenerated electron–hole pair with roughly 2 nm separation. At higher photon energy, more expanded pairs are produced incoherently via thermalization.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie - Univ.-Prof. Dr. Anna Köhler
Faculties
Faculties > Faculty of Mathematics, Physics und Computer Science
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 530 Physics
Date Deposited: 07 Dec 2016 12:19
Last Modified: 07 Dec 2016 12:19
URI: https://eref.uni-bayreuth.de/id/eprint/35405