In p-type doping, the molecular dopant is often chosen such that its lowest unoccupied molecular orbital (LUMO) is lower in energy than the highest occupied molecular orbital (HOMO) of the conjugated polymer. The molecular dopant 2,3,5,6-tetrafluoro-7,7,8,8tetracyanoquinodimethane (F 4 TCNQ) with LUMO at ∼ 5.24 eV is popularly used as ptype dopant for the prototypical polymer system, poly(3-hexylthiophene) (P3HT) with the HOMO at ∼ 5 eV. The molecular structures of the mentioned molecular systems are shown in Fig. . Via integer charge transfer, the P3HT/F 4 TCNQ system forms an ion-pair (IP) of dopant anion and polymer cation with accompanying nuclear reorganization around the charge separated state, i.e. polaron formation. The poor doping efficiency in this system signifies that the charges created via doping are not free. Even at high dopant loading conditions of 20 % maximum conductivity achieved is ∼ 10 S cm -1 . The Neher group has employed quantitative analysis of the specific near-infrared absorption bands of (F 4 TCNQ) anion to reveal that nearly every (F 4 TCNQ) dopant undergoes integer charge transfer with (P3HT) matrix. However, only about 5 % fraction of charges dissociate to actually contribute a free hole for electrical conduction, while the remaining 95 % fraction remains strongly bounded.