ИСТИНА

Single crystals of thiophene-phenylene co-oligomers (TPCO) have demonstrated high potential for organic optoelectronics due to unique combination of high charge carriers mobility and excellent photoluminescence (PL) efficiency [1]. Despite a considerable amount of experimental research, the detailed understanding of high PL in TPCO single crystals is still lacking. Time-resolved, polarization-sensitive PL parameters can provide important insights for establishing the relationship between the molecular structure and optical properties of TPCO. In this contribution, we analyze time-resolved PL anisotropy in a TPCO crystal based on the 1,4-bis{5-[4-(trimethylsilyl)phenyl]thiophen-2-yl}benzene molecule. X-ray diffraction experiments indicated the herringbone packing motif as have been reported for crystals based on analogous TPCO with the same terminal group [1]. Regardless of the excitation polarization, PL is mainly polarized along the molecule axis. However, quite surprisingly, PL induced by the excitation orthogonally polarized with respect to the molecular axis exhibits much higher intensity as compared to the parallel one. Such an unexpected PL anisotropy geometry is discussed in relation to the J-aggregates crystal packing and the impact of a luminescent impurities. This work was partially supported by Russian Science Foundation (grant 15-12-30031). [1]S.Hotta et al.,JMCC, 2(6),965(2014); L. Kudryashova et al., ACS Appl. Mater. Interfaces, 8(16),10088(2016)