Work

Probing Nanoscale Carrier Dynamics in P3HT Blended with a Non-Fullerene Acceptor: Impact of Mixing on Device-Relevant Carrier Generation

Year: 2026

Type: preprint

Abstract: High-performing organic photovoltaics (OPVs) rely not only on the appropriate energetics and interfaces for separating excitons into charges, but on distinct areas of donor-rich and acceptor-rich domains to transport those charges to electrodes once separated. In this work, we study a bulk heterojunction (BHJ) of well-studied poly(3-hexylthiophene-2,5-diyl) (P3HT) and a non-fullerene acceptor with an A1-D-A2-D-A1 motif, octyl rhodanine-thiophene-benzothiadiazole-thiophene-octyl rhodanine (ORTBT). Using device characterization and time-resolved spectroscopic techniques, we show that despite promising picosecond photophysical properties P3HT:ORTBT blends do not lead to long-lived charges due to overly-imbalanced mixing between the ORTBT acceptor and P3HT donor on length scales that are either too small or too large. We compare results with a prototypical BHJ, P3HT and PC61BM fullerene to understand the photophysical differences in the exciton dissociation dynamics. The significant mixing in P3HT:ORTBT disrupts the crystalline regions of the P3HT that are necessary for effective hole transport. This work demonstrates the need to consider both the chemical and physical properties of non-fullerene acceptors to achieve an optimal balance of donor-acceptor mixing that facilitates high exciton dissociation efficiency and long-lived carrier transport pathways in the bulk.

Source: ChemRxiv

DOI: 10.26434/chemrxiv.15009722/v1