Solar cells based on blends of the donor polymer, P3HT, with the non-fullerene acceptor, IDTBR, have been shown to exhibit promising efficiencies and stabilities for low cost organic photovoltaic (OPV) devices. We focus herein on the charge separation and recombination dynamics in such devices. By employing selective wavelength excitations of P3HT and O-IDTBR, we show that photoexcitation of the P3HT results in lower internal quantum efficiency (IQE) for photocurrent generation than observed for photoexcitation of the O-IDTBR. Transient absorption and photoluminescence quenching studies indicate that this lower IQE results primarily from higher geminate recombination losses of photogenerated charges following P3HT excitation compared with O-IDTBR excitation, rather than from differences in exciton separation efficiency. These higher geminate recombination losses result not only in a lower photocurrent generation efficiency at short circuit, but also a lower device J-V fill factor upon selective excitation of the P3HT donor, when compared with O-IDTBR excitation.
|Original language||English (US)|
|Number of pages||7|
|Journal||The Journal of Physical Chemistry C|
|State||Published - Dec 24 2018|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): OSR-2015-CRG-2572
Acknowledgements: The authors declare no competing financial interests. The author CH Tan thanks Malaysian Government MyBrainSc for the funding and also Matthew Davies from Swansea University for providing PL excitation spectroscopy instrument. Funding from the KAUST project OSR-2015-CRG-2572 is gratefully acknowledged. The authors also thank KAUST for financial support and acknowledge EC FP7 Project SC2 (610115), EC H2020 (643791), and EPSRC Projects EP/G037515/1 and EP/M005143/1.