Photoluminescence: Science and applications

Abstract

In the past five years photoluminescence (PL) of SWNTs has gone from discovery to one of the most actively researched areas, with broad impact on the basic science of SWNTs, as well as the promise of applications. The simplest free-carrier models of perfect semiconducting SWNTs in vacuum predict that they have direct bandgaps and therefore should be efficient light absorbers and emitters. Experimentally, isolating SWNTs from environmental interactions proves crucial to observing this strong PL. The Coulomb interaction enhanced by one-dimensional confinement requires that excitonic models be invoked to understand PL features. Prepared properly, SWNTs are strong PL emitters, with good quantum yield, showing principal PL peaks with characteristic lineshapes and (n,m)-dependent emission and absorption energies, as well as a rich absorption spectrum. PL has emerged as an important characterization tool for determining (n,m) and (n,m) distributions, albeit with some limitations. Extrinsic factors, such as chemical environment, temperature, electric and magnetic field, or intrinsic factors, such as phonons, are manifest in SWNT PL. Possible applications in sensing, biological markers, and optoelectronics are beginning to emerge from current research in SWNT PL.