Molecular Dioxygen-Mediated Passivation of Electron Traps in n-Type Organic Charge-Transfer Complexes

The inherent susceptibility of n-type organic semiconductors to molecular dioxygen (O₂) results in electron trapping or in unintended p-doping, which in turn diminishes their electron mobility. This concept is challenged in the present study by exploring O₂ interactions with organic charge-transfer complexes (CTCs), where electron donor-acceptor interactions generate partially delocalized electronic states. Using a CTC comprising a phenazine electron donor and a 7,7,8,8-tetracyanoquinodimethane (TCNQ) electron acceptor, we demonstrate that its exposure to O₂ does not lead to electron extraction but instead enhances the charge-transfer activity. The increased electron density at the TCNQ acceptor upon CTC exposure to O₂ is attributed to electron trap-states passivation by O₂, without evidence of chemisorption. This passivation mitigates recombination losses, resulting in a threefold photoluminescence quantum yield increase, enhanced electrical conductivity, and improved charge-transfer state efficiency. Similar O₂-mediated conductivity enhancements are observed across additional donor-acceptor pairs, proving the broader applicability of this effect, and paving the way for designing O₂-enhanced advanced organic electronic materials.