TY  - JOUR
A1  - Bartesaghi, Davide
A1  - Perez, Irene del Carmen
A1  - Kniepert, Juliane
A1  - Roland, Steffen
A1  - Turbiez, Mathieu
A1  - Neher, Dieter
A1  - Koster, L. Jan Anton
T1  - Competition between recombination and extraction of free charges determines the fill factor of organic solar cells
T2  - Nature Communications
N2  - Among the parameters that characterize a solar cell and define its power-conversion efficiency, the fill factor is the least well understood, making targeted improvements difficult. Here we quantify the competition between charge extraction and recombination by using a single parameter theta, and we demonstrate that this parameter is directly related to the fill factor of many different bulk-heterojunction solar cells. Our finding is supported by experimental measurements on 15 different donor: acceptor combinations, as well as by drift-diffusion simulations of organic solar cells in which charge-carrier mobilities, recombination rate, light intensity, energy levels and active-layer thickness are all varied over wide ranges to reproduce typical experimental conditions. The results unify the fill factors of several very different donor: acceptor combinations and give insight into why fill factors change so much with thickness, light intensity and materials properties. To achieve fill factors larger than 0.8 requires further improvements in charge transport while reducing recombination.
Y1  - 2015
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/38954
SN  - 2041-1723
VL  - 6
PB  - Nature Publ. Group
CY  - London
ER  -