Photocurrent contribution from inter-segmental mixing in donor–acceptor-type polymer solar cells: A multiscale simulation study

• Published in: Polymer (Guilford) 2014-08, Vol.55 (16), p.3736-3745
• Main Authors: Pershin, Anton, Donets, Sergii, Baeurle, Stephan A.
• Format: Article
• Language: English
• Subjects: Algorithms; Computer simulation; Current density; Development and application of multiscale simulation algorithm for the study of photovoltaic behavior of donor-acceptor-type polymer solar cells; Devices; Electronics; Lamellar-like PFB-F8BT blend with F8BT phase in reduced and photo-oxidized form; Nanostructure; Photocurrent contribution from intersegmental mixing at donor–acceptor interface; Photovoltaic cells; Solar cells
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2014.06.038

Polymer solar cells possess a promising perspective for generating renewable energy at affordable costs, provided their performance and durability can be improved considerably. To this end, several experimental and theoretical techniques have been devised recently, establishing a direct link between local morphology, local opto-electronic properties and device performance. However, their reliability is still unclear to this day. Here, we demonstrate by using a recently developed particle-based multiscale solar cell approach and comparing its results with the ones of a field-based solar cell algorithm that inter-mixing of the electron-donor(D)- and -acceptor(A)-type of segments in a lamellar-like poly(9,9’-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylene-diamine)-poly(9,9'-dioctylfluorene-co-benzothiadiazole) (PFB-F8BT) blend causes that the major part of the charge generation and charge transport takes place inside the nanophases of the nanostructured polymer solar cells in agreement with recent experimental measurements and not, as commonly believed, at the visible domain boundaries of the DA interface. Moreover, we show that the contribution of the exciton dissociation efficiency to the internal quantum efficiency, due to inter-monomeric mixing, is significant and cannot be neglected in simulation studies at the nanoscale. Finally, we demonstrate that keto-defects on the fluorene moiety of the F8BT phase, induced by photo-oxidation, causes a simultaneous increase of the intra-chain contribution and decrease of the inter-chain contribution to the electronic current density, whereas in the reduced form the difference between both contributions is significantly smaller. This antagonistic effect leads to keto-induced electron trapping, resulting in a deteriorated electronic transport efficiency in devices with a photo-oxidized F8BT phase. [Display omitted] •Development of a novel particle-based multiscale solar cell algorithm using field-to-particle transformation.•Investigation of inter-mixing of donor- and acceptor-type of monomers in a nanostructured PFB-F8BT blend.•Results show that charge-generation- and -transport occur predominantly inside the nanophases.•Photo-induced keto-defects on F8BT polymers cause intra-chain electron-trapping, reducing electron transport efficiency•Outcome is in agreement with recent electrostatic-force- and photocurrent-microscopy-experiments.