Skip to main content



Free and open to the public


CREOL, Room 102


The processes of photon energy upconversion (UC), where locally (or in situ) photons strongly blue shifted regarding the excitation wavelength have been intensively studied. Different UC-techniques, including Two-Photon Absorption (TPA), Energy Transfer Upconversion (ETU) have been used. As optical excitation near infrared (NIR) or infra red (IR) light sources are used.

In contrast to the all previously described UC-techniques the fundamental advantage of the energetically conjoined triplet-triplet annihilation up-conversion (TTA -UC) is its inherent independence on the coherence of the excitation light. Another principal advantage of TTA - UC process is the very low required intensity (as low as 20 mWcm-2) and extremely low spectral power density (as low as 125μWnm-1) of the excitation source needed - so it can in reality be the Sun.

We present the summarised results of our investigations and experiments and state the general requirements for the materials' parameters of the couple sensitizer/emitter in order to obtain efficient energetically conjoined TTA-UC. We also present our working UC-devices for spectrum concentration via UC with up-converted fluorescence quantum yield of 3.2% realized at ultra-low excitation intensities (~ 20 mWcm-2).