Year-end Sale % OFF 
Abstract
Fermi level control by doping is established since decades in inorganic semiconductors and has been successfully introduced in organic semiconductors. Despite its commercial success in the multi-billion OLED display business, molecular doping is little understood, with its elementary steps controversially discussed and mostly-empirical-materials design. Particularly puzzling is the efficient carrier release, despite a presumably large Coulomb barrier. Here we quantitatively investigate doping as a two-step process, involving single-electron transfer from donor to acceptor molecules and subsequent dissociation of the ground-state integer-charge transfer complex (ICTC). We show that carrier release by ICTC dissociation has an activation energy of only a few tens of meV, despite a Coulomb binding of several 100 meV. We resolve this discrepancy by taking energetic disorder into account. The overall doping process is explained by an extended semiconductor model in which occupation of ICTCs causes the classically known reserve regime at device-relevant doping concentrations.
Highlights
The conductivity was identified to super-linearly scale with the dopant concentration for ZnPc:F6-TCNNQ10, despite the evidence for the reserve regime
This work demonstrates that molecular doping is a two-step process, comprising single-electron transfer from donor to acceptor molecules, and subsequent dissociation of formed [D+A −] ICTCs, which determine the overall doping efficiency in excitonic organic semiconductors
The concentration and temperature dependence of the doping efficiency is well explained in framework of an extended semiconductor statistics description in which ICTC occupation causes the classically known reserve regime even for 100% dopant ionization
Summary
This fingerprint is distinct from possibly formed supramolecular D+δA−δ complexes with fractional charge transfer (CT), δ < 1, whose absorption is characterized by optical transitions of the form D+δA−δ → D+1− δA−1+ δ 39,42. The energetic doping ratio, attributed to F6distance of the ZnPc Q-bands reduces, accompanied by a decrease of the π–π interaction peak (610 nm)[44], which indicates suppressed crystal-phase formation[21]. Apart from that, absorption of neutral F6-TCNNQ molecules is found (520 nm peak, Supplementary Figure 1), indicating an incomplete hostdopant ICT at higher doping ratios. For p-doped MeO-TPD films, various sub-gap absorption features appear besides the. We study the relative degree of ICT under temperature variation, shown, d for representative p-doped films of each host. The F6Similar findings hold for the cationic host absorptions, clearly visible for MeO-TPD+ (cf 490 and 710 nm features), and for lower and higher doping ratios (Supplementary Figure 1). To estimate doping efficiency and free hole activation p(T), Mott–Schottky analysis[18] under temperature variation is performed on indium tin oxide (ITO)/host:F6-TCNNQ(50 nm)/aluminum(Al) diodes utilizing ZnPc and MeO-TPD. The 1/Cd2(V) plots for 150 < T < 290 K are given in
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
