Organic Heptamethine Salts for Photovoltaics and Detectors with Near‐Infrared Photoresponse up to 1600 nm

A new series of cationic heptamethine salts with selective deep near-infrared photoresponse are demonstrated having photoresponse cutoffs between λ = 1400 and 1600 nm. Anion exchange and alloying allows for fine energy level tuning to increase open-circuit voltages, photodetector detectivities, and provide insight into the exciton binding energies of these very small bandgap organic salts.