Tiny salt molecules unlock big efficiency gains in next-gen electronics
Researchers discovered that the size of salt molecules used in organic semiconductor manufacturing dramatically improves electrical performance—boosting conductivity up to 2000 S/cm. The finding could accelerate commercialization of flexible electronics, solar cells, and batteries by simplifying production while cutting costs.
Originaltitel: Counterion-Controlled Photocatalytic Doping of Organic Semiconductors
Valet av motjoner i fotokatalytisk dopning styr effektiviteten i organiska halvledare — en funktion som tidigare inte systematiskt undersökts. Forskare vid Linköpings universitet visar att mindre anjoner, särskilt bis(fluorosulfonyl)imid (FSI-), förbättrar ledningsförmågan i PBTTT-derivat upp till 2000 S cm⁻¹. Det sker genom att FSI- minskar aggregation av fotokatalysatorerna och ökar elektronaffiniteten med cirka 0,1 eV jämfört med större anjoner. Studien kombinerar spektroskopi och densitetsfunktionalteori för att kartlägga mekanismerna bakom effekten. För investerare i organisk elektronik innebär detta att motjonvalet blir en styrhävstång för att optimera ladningstransport utan att behöva ändra själva materialen. Upptäckten möjliggör milder processförhållanden och kan påskynda kommersialisering av hållbar organisk elektronik för energilagring och växelriktare.
<p>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-) suppress PC aggregation, enhance electron transfer, and yield conductivities up to 2000 S cm-1 in PBTTT derivatives. Spectroscopic and density functional theory (DFT) analyses show that FSI- disrupts Acr-Me+ stacking and increases its electron affinity by similar to 0.1 eV relative to bulkier anions. These results uncover counterion size as a key design parameter for optimizing photocatalytic doping in OSCs.</p>