TY  - JOUR
A1  - Kurpiers, Jona
A1  - Ferron, Thomas
A1  - Roland, Steffen
A1  - Jakoby, Marius
A1  - Thiede, Tobias
A1  - Jaiser, Frank
A1  - Albrecht, Steve
A1  - Janietz, Silvia
A1  - Collins, Brian A.
A1  - Howard, Ian A.
A1  - Neher, Dieter
T1  - Probing the pathways of free charge generation in organic bulk heterojunction solar cells
JF  - Nature Communications
N2  - The fact that organic solar cells perform efficiently despite the low dielectric constant of most photoactive blends initiated a long-standing debate regarding the dominant pathways of free charge formation. Here, we address this issue through the accurate measurement of the activation energy for free charge photogeneration over a wide range of photon energy, using the method of time-delayed collection field. For our prototypical low bandgap polymer:fullerene blends, we find that neither the temperature nor the field dependence of free charge generation depend on the excitation energy, ruling out an appreciable contribution to free charge generation though hot carrier pathways. On the other hand, activation energies are on the order of the room temperature thermal energy for all studied blends. We conclude that charge generation in such devices proceeds through thermalized charge transfer states, and that thermal energy is sufficient to separate most of these states into free charges.
Y1  - 2018
U6  - https://doi.org/10.1038/s41467-018-04386-3
SN  - 2041-1723
VL  - 9
PB  - Nature Publ. Group
CY  - London
ER  -