High-mobility, trap-free charge transport in conjugated polymer diodes

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Nikolka, Mark 
Broch, Katharina 
Hanifi, David 
Nowack, Peer 

Charge transport in conjugated polymer semiconductors has traditionally been thought to be limited to a low mobility regime by pronounced energetic disorder. Much progress has recently been made in advancing carrier mobilities in field-effect transistors through developing low-disorder conjugated polymers. However, in diodes these polymers have to date not shown much improved mobilities, presumably reflecting the fact that in diodes lower carrier concentrations are available to fill up residual tail states in the density of states. Here, we show that the bulk charge transport in low-disorder polymers is limited by water-induced trap states and that their concentration can be dramatically reduced through incorporating small molecular additives into the polymer film. Upon incorporation of the additives we achieve space-charge limited current characteristics that resemble molecular single crystals such as rubrene with high, trap-free SCLC mobilities up to 0.2 cm2/Vs and a width of the residual tail state distribution comparable to kBT.

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Nature Communications
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Nature Publishing Group
European Research Council (610115)
We gratefully acknowledge financial support the Engineering and Physical Sciences Research Council (EPSRC) through a Programme Grant (EP/M005141/1). M.N. acknowledges financial support from the European Commission through a Marie-Curie Individual Fellowship (EC Grant Agreement Number: 747461).
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