Near-Infrared Electroluminescence from Ambipolar Transistors Built on sp³-Functionalized Carbon-Nanotube Networks

We demonstrate room-temperature, near-infrared electroluminescence (EL) from networks of sp³-functionalized (6,5) single-walled carbon nanotubes (SWCNTs) using ambipolar transistors with sub-10 μm channels. EL efficiency dependences on drain current and channel length are investigated, giving insights into the carrier recombination in SWCNT networks. EL from free and localized excitons are strongly limited by trap-assisted Shockley-Read-Hall (SRH) recombination; high emission efficiency can be achieved in short channels down to 2 μm with the alleviation of SRH recombination. A substantial drop in efficiency is observed in the 1 μm channel, signifying the onset of incomplete carrier recombination. Moreover, electroluminescence from localized trions (∼1405 nm) is observed for the first time with additional emission peaks from free excitons (∼1009 nm), free trions (∼1170 nm), and localized excitons (∼1264 nm). The trion and localized trion-emissions are interdependent to each other, confirming that the localized trion is formed through a free trion captured by a sp³ defect.