ABSTRACT: Doping is a powerful method to optimize the electrical characteristics of organic semiconductors, but a comprehensive picture capturing the phenomena at play is still under development. In this work, combining UV-vis absorbance spectroscopy with ultraviolet and X-ray photoelectron spectroscopy, we investigate the p-type doping of (sub)-monolayer films of two structurally isomeric organic semiconductors on graphite, naphtho-[2,3-b]-thieno-[2‴,3‴:4″,5″]-thieno-[2″,3″:4',5']-thieno-[3',2'-b]-naphtho-[2,3-b]-thiophene (DN4T) and naphtho-[1,2-b]-thieno-[2‴,3‴:4″,5″]-thieno-[2″,3″:4',5']-thieno-[3',2'-b]-naphtho-[1,2b]-thiophene (isoDN4T), with the strong molecular acceptor 2,2'-(perfluoronaphthalene-2,6-diylidene)-dimalononitrile (F6TCNNQ). For DN4T, a hybrid highest occupi
