Enhanced Photostability and Red-NIR Photosensitivity of Conjugated Polymer Charge-Transfer Complexes

A promising route to photostable and low-bandgap polymer materials for optoelectronic and photonic applications could be utilization of donor-acceptor ground-state charge-transfer complexes (CTCs) of wide-bandgap conjugated polymers. In this work, we report our results on photostability and photoelectric studies of CTC between an archetypical conjugated polymer MEH-PPV and low-molecular-weight acceptor 2,4,7-trinitrofluorenone (TNF). By using the pump-probe laser photobleaching technique, we show that the photodegradation rate of MEH-PPV:TNF blend films decreases up to four orders of magnitude as compared with pristine MEH-PPV. By using photocurrent and surface photovoltage spectroscopies, we demonstrate that the photoelectric sensitivity of the MEH-PPV:TNF CTC can be deeply extended in the polymer optical gap down to 1 µm. However, the main drawback of the CTC studied is their low charge collection efficiency, and an approach to increasing it is discussed.