Since the 1960s, poly(benzobisimidazobenzophenathrolinedione) (BBL) has been the only n-type ladder-type conjugated polymer (LCP) that is utilized in thin film electronic devices. Its high electrochemical and thermal stabilities make it a promising candidate for organic electrochemical transistors (OECTs) and thermoelectrics (OTEs) applications. Here we report the synthesis and characterization of a new π-extended poly(benzimidazoanthradiisoquinolinedione) (BAL). The tetrachlorinated BAL (Cl4-BAL) is fully soluble in methanesulfonic acid (MSA) and can be spin-coated into good quality thin films, enabling the fabrication and characterization of OTEs. Doping of Cl4-BAL films using our in-house benzyl viologen radical cation (BV●+) n-dopant shows better electrical air-stability as compared to BBL due to its very low LUMO value (-4.83 eV), making it a promising material toward air-stable n-doped conducting polymers.