Counterion-Controlled Photocatalytic Doping of Organic Semiconductors.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41926061.
- Also identified by DOI 10.1002/adma.72947 and PMC identifier 13137766.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Photocatalytic doping is a versatile and potentially sustainable strategy to control charge accumulation and transport in organic semiconductors (OSCs). In this process, light-activated photocatalysts (PCs) act as electron shuttles, oxidizing or reducing OSCs under mild conditions, while redox-inert salts supply counterions to stabilize the resulting charges. Although the energetics of PC/OSC systems are well studied, the influence of counterions has not yet been systematically examined. Here, we show that counterion size and interaction with the PC critically govern photocatalytic doping efficiency. Using acridinium-based PCs with lithium salts of varying anion size, we find that smaller anions such as bis(fluorosulfonyl)imide (FSI<sup>-</sup>) suppress PC aggregation, enhance electron transfer, and yield conductivities up to 2000 S cm<sup>-1</sup> in PBTTT derivatives. Spectroscopic and density functional theory (DFT) analyses show that FSI<sup>-</sup> disrupts Acr-Me<sup>+</sup> stacking and increases its electron affinity by ∼0.1 eV relative to bulkier anions. These results uncover counterion size as a key design parameter for optimizing photocatalytic doping in OSCs.