Reducing non-radiative voltage losses by methylation of push-pull molecular donors in organic solar cells

Lukasz Baisinger (1) , José María M Andrés Castán (2) , Pablo Simón Marqués (2) , Giacomo Londi (3) , Clemens Göhler (4) , Carsten Deibel (4) , David Beljonne (3) , Clément Cabanetos (2) , Philippe Blanchard (2) , Johannes Benduhn (1) , Donato Spoltore (1) , Karl Leo (1)

1 TU Dresden - Technische Universität Dresden = Dresden University of Technology
2 MOLTECH-Anjou
3 UMons - Université de Mons
4 Chemnitz University of Technology / Technische Universität Chemnitz

Organic solar cells are approaching power conversion efficiencies of other thin-film technologies. However, in order to become truly market competitive, the still substantial voltage losses need to be reduced. Here, we describe the synthesis and characterization of four novel arylamine-based push-pull molecular donors, two of them exhibiting a methyl group at the para position of the external phenyl ring of the arylamine block. By assessing the charge-transfer state properties and the effects of methylation on the open-circuit voltage of the device, we show that devices based on methylated versions of the molecular donors exhibit reduced voltage losses due to decreased non-radiative recombination. Modelling suggests that methylation results in a tighter interaction between donor and acceptor molecules, turning into a larger oscillator strength to the charge-transfer states, thereby ensuing reduced non-radiative decay rates.

Domaines: Chimie organique

Lukasz Baisinger, José María M Andrés Castán, Pablo Simón Marqués, Giacomo Londi, Clemens Göhler, et al.. Reducing non-radiative voltage losses by methylation of push-pull molecular donors in organic solar cells. ChemSusChem, 2021, Advanced Organic Solar Cells, 14 (17), pp.3622-3631. ⟨10.1002/cssc.202100799⟩. ⟨hal-03389380⟩