Boosting Photo Upconversion in Electropolymerised Thin Film with Yb/Er Complexes

Upconversion luminescence (UCL) in organometallic complexes has attracted great interest in photovoltaics and biological applications due to their fascinating energy transfer mechanism from low-energy photon to high-energy photon. However, photon-upconversion operating in a single discrete entity remains a challenge caused by low-absorption cross section of the luminescent lanthanide element. Here, a novel upconversion system is reported combining Yb (Ytterbium) sensitizers and Er (Erbium) activators in the film by electropolymerization, which leads to excited-state absorption (ESA) and energy transfer upconversion (ETU) processes. For the first time, the UCL has been achieved in the thin films upon near-infrared laser irradiation, and the upconversion intensity exhibits up to 30-fold enhancement with the variation of Yb/Er ratio.