Characterization of Charge-Carrier Transport in Semicrystalline Polymers: Electronic Coupling, Site Energies, and Charge-Carrier Dynamics in Poly(bithiophene-alt-thienothiophene) [PBTTT]статья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 18 декабря 2013 г.
Аннотация:We establish a link between the microscopic
ordering and the charge-transport parameters for a highly
crystalline polymeric organic semiconductor, poly(2,5-bis(3-
tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT).
We find that the nematic and dynamic order parameters of
the conjugated backbones, as well as their separation, evolve
linearly with temperature, while the side-chain dynamic order
parameter and backbone paracrystallinity change abruptly
upon the (also experimentally observed) melting of the side
chains around 400 K. The distribution of site energies follows
the behavior of the backbone paracrystallinity and can be treated as static on the time scale of a single-charge transfer reaction. On the contrary, the electronic couplings between adjacent backbones are insensitive to side-chain melting and vary on a much faster time scale. The hole mobility, calculated after time-averaging of the electronic couplings, reproduces well the value measured in a short-channel thin-film transistor. The results underline that to secure efficient charge transport in lamellar arrangements of conjugated polymers: (i) the electronic couplings should present high average values and fast dynamics, and (ii) the energetic disorder (paracrystallinity) should be small.