Dithiazolylthienothiophene bisimide (TzBI) is a promising building unit for donor-acceptor pi-conjugated polymers due to its strong electron-deficiency and high coplanarity. We previously reported a TzBI-based pi-conjugated polymer functioned as n-type semiconductor in organic photovoltaic cells. However, a critical deficiency was that the molecular weight of the polymer was not sufficiently high. It is also important to investigate the possibility of TzBI-based polymers as a p-type semiconductor. In this study, we show that a new synthetic approach gave a new TzBI-based polymer with an improved molecular weight relative to the previously reported polymer. Further, having a co-building unit with a more electron-rich nature, the polymer functioned as p-type semiconductor in organic photovoltaic cells when the PC61BM was used as ntype material. This study shows that TzBI is a versatile building unit for pi-conjugated polymers that can be used in organic electronic devices.