Photoconduction and magnetic field effect on photoconduction in hole-transporting star-burst amine (m-MTDATA) films

Singlet Exciton Diffusion in Vacuum‐Evaporated Films of Amine‐Based Materials as Studied by Photocurrent and Photoluminescence Quenching Methods

“…As the photoluminescence measured in the SR‐PLQ method is due to the radiative emission of singlet excitons, one may conclude that the j + photocurrents in the m‐MTDATA and 2TNATA films are generated by dissociation process of singlets at the illuminated, Al(+), sample electrodes. This observation coincides with the outcomes of our previous experiments on photocurrents in external magnetic field in such layers, where the photocurrent arising on the anode of the Al/m‐MTDATA/Al structure is not affected by magnetic field …”

“…The accordance between outcomes of optical and electrical measurements suggests that the photocurrent in the films of m‐MTDATA and 2TNATA arises due to dissociation of singlet excitons on the illuminated anode, Al(+). This observation confirms results of our previous investigations of photocurrents in external magnetic field in such layers . It is worth noting here that the photocurrent generated on the anode of the Al/m‐MTDATA/Al structure is not affected by magnetic field, whereas that arising in the layer bulk (with the triplet entities: electron–hole pairs and molecular triplet excitons involved), turns out to be magnetic field sensitive.…”

“…The applicability of this technique requires, however, the photoconductivity of the samples not to be significantly contributed by the volume generation current. This feature was carefully controlled before measurements …”

“…Apart from presenting the results of our measurements carried out with the use of well‐established techniques, the present paper provides for the first time a systematic comparison and detailed discussion of the diffusion length data in commonly applied amine‐based materials, mainly as the hole transporters in optoelectronic devices. Nevertheless, the studies on exciton dynamics and diffusive motion as well as deciding on the type of excitons (singlet or triplet) involved in electrode processes are essential for understanding of the magnetic effects in electroluminescent and photovoltaic systems, widely discussed in the literature …”