We demonstrate improved compatibility of poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole transport layer with acid-sensitive materials by addition of a simple base, NaOH or NH4OH, to the aqueous suspension to increase pH. Addition of NaOH to the acidic PEDOT:PSS allowed the deposition of PEDOT:PSS on top of an inverted poly(3-hexylthiophene):ZnO nanoparticle blend hybrid photovoltaic device, and improved device performance due to preservation of the ZnO electron acceptor. To quantitatively investigate the impact of base addition to hole transport layer properties and device performance, we deposited PEDOT:PSS with different pH values on inverted poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester bulk heterojunction devices. We find that NaOH modification results in a substantial work function decrease and series resistance increase. In contrast, the volatile NH4OH leaves PEDOT:PSS with minimal changes in film properties and device performance.