Ambipolar semiconducting polymers, characterized by both high electron (μ_e) and hole (μ_h) mobility, offer the advantage of realizing complex complementary electronic circuits with a single semiconducting layer, deposited by simple coating techniques. However, to achieve complementarity, one of the two conduction paths in transistors has to be suppressed, resulting in unipolar devices. Here, we adopt charge injection engineering through a specific interlayer in order to tune injection into frontier energy orbitals of a high mobility donor-acceptor co-polymer. Starting from field-effect transistors with Au contacts, showing a p-type unbalanced behaviour with μ_h = 0.29 cm²/V s and μ_e = 0.001 cm²/V s, through the insertion of a caesium salt interlayer with optimized thickness, we obtain an n-type unbalanced transistor with μ_e = 0.12 cm²/V s and μ_h = 8 × 10⁻⁴ cm²/V s. We applied this result to the development of the basic pass-transistor logic building blocks such as inverters, with high gain and good noise margin, and transmission-gates. In addition, we developed and characterized information storage circuits like D-Latches and D-Flip-Flops consisting of 16 transistors, demonstrating both their static and dynamic performances and thus the suitability of this technology for more complex circuits such as display addressing logic.