Rubrene is a well-known TTA emitter and an electron donor, whereas Y6 has recently been developed as an efficient non-fullerene acceptor (NFA) in the field of organic photovoltaics (OPVs) and can absorb NIR light (Figure ). Bright yellow emission by NIR excitation could be observed on the bilayer. The emission spectrum of the rubrene/Y6 bilayer film in Figure had the same shape as the rubrene photoluminescence (PL) in Figure . Furthermore, the pristine rubrene film did not exhibit any emission peaks upon 850 nm LED irradiation. Therefore, the emission with a peak top of 565 nm by the 850 nm irradiation in the rubrene/Y6 bilayer film was certainly UC emission originating from the donor/acceptor (D/A) interface. The value of the apparent anti-Stokes shift, i.e. energy difference between the lowest energy absorption peak of the sensitizer and emission peak of the emitter, was high, at 0.71 eV.