Invited Paper EM2-ThA10
Controlling the Electronic Structure of Organic Semiconductors via Doping

Thursday, November 13, 2014, 5:20 pm, Room 314

Typical organic (molecular and polymer) semiconductors (OSC) used in organic light emitting diodes, filed-effect transistors or photovoltaic cells have energy gaps upwards of 1.5-2 eV and have very low conductivity due to the exceedingly small density of “free” carriers and the localized nature of these carriers. Chemical doping has proven to be an extremely powerful tool for controlling the electronic structure of these materials, in particular for improving charge carrier injection at contacts. This talk will review recent developments in the area of chemical doping of OSCs [1,2]. The reducing or oxidizing power of a number of n- and p-type organic dopants are reviewed, along with their impact on the electronic structure and conductivity of both vacuum- or solution-processed OSC films. In particular, the talk will outline recent work aimed at passivating, or compensating, deep electronic gap states, or traps, which are due to structural or chemical imperfections and profoundly affect interface energetic and carrier transport [3]. The process implies the control of ultra-low concentrations of dopants just sufficient to fill traps states and render them inactive, without adding significant densities of “free” carriers in the system. Impact on device characteristics will be reviewed [4].

[1] C. K. Chan et al. Org. Elect. 9, 575 (2008)

[2] G. Song et al. Adv. Mat. 24, 699 (2012)

[3] S. Olthof et al., Phys. Rev. Lett. 109, 176601 (2012)

[4] S. Olthof et al., Appl. Phys. Lett. 101, 253303 (2012)