One of the most effective strategies for enhancing the stability of polycyclic aromatic hydrocarbons (PAHs) involves substituting some of their carbon atoms with main group element heteroatoms, such as sulfur (S), nitrogen (N), boron (B), or phosphorus (P). Such heteroatom substitution not only significantly improves their stability but also endows the resulting polycyclic heteroaromatic compounds with a broad spectrum of properties that are unattainable by their purely hydrocarbon analogues. Besides fine-tuning the electronic structure, heteroatoms can improve molecular packing, and processability, opening new avenues for material design and application. Thiophenes and azaacenes, in particular, have been the subject of extensive research due to their remarkable potential in organic electronic devices for their transformative impact on the performance and functionality of these materials. Derivatives of indole and its isomers, isoindole and indolizine are among the less studied PACs for organic optoelectronics (Figure ). A recent theoretical investigation by Pino-Rios and Solà has cast these molecules in a new light, revealing significant insights into their relative stability. Their research uncovered a pronounced disparity in the distribution of local aromaticity within these structures, which is influenced by the positioning of the nitrogen atom. The difference in the HOMO-LUMO energy gap between indole and indolizine of 0.88 eV is attributed solely to the variations in nitrogen position within their frameworks. Pino-Rios and Solà concluded that the relatively lower stability of isoindole and indolizine is the result of the reduction of the aromaticity in the 6-membered ring as a manifestation of the Glidewell-Lloyd rule. Such striking difference in aromatic stabilization and the delocalization of electrons between indole and its isomers offers a unique avenue for tailoring the optoelectronic properties of polycyclic aromatic compounds through strategic incorporation and substitution of these heterocycles. While π-expanded derivatives of indole have been the subject of considerable study, the integration of indolizines into polycyclic aromatic frameworks remains surprisingly sparse. In this context, we have embarked on a quest to merge indole and indolizine within a single polycyclic molecular architecture, which we coined indoloindolizine (Figure ), aiming to enable the precise modulation of the electronic structure for optoelectronic applications, in particular stable organic field-effect transistors (OFETs). We elucidate molecular design principles aimed at adjusting the HOMO-LUMO gap by the interplay between indole and indolizine-type characters. We developed a straightforward and efficient synthesis methodology for a diverse array of π-expanded derivatives and conducted a thorough investigation of their optoelectronic properties. The study is further enriched by extensive theoretical analyses that shed light on the seemingly counterintuitive phenomenon of an increasing band gap with an expanding conjugated π-system.