BiCuSeO is a widely-used thermoelectric material recently proved to be an appealing candidate for broadband photothermoelectric (PTE) detection. Developing a simple and scalable route for advancing PTE properties is therefore essential to explore the full potential of BiCuSeO. Here we systematically demonstrated that Co3+ atomic doping strategies in BiCuSeO single crystals (Co concentration of 1%, 2% and 4%) could modulate the Seebeck coefficient and thus strongly improve the performance of BiCuSeO PTE photodetectors across visible to infrared spectral regions. Benefiting from these strategies, a large enhancement on photovoltage responsivity is achieved and the response time of a 4% Co:BiCuSeO PTE photodetector is one order of magnitude faster than those in most of PTE photodetectors. Also, Co:BiCuSeO PTE photodetectors show good stability with changeless photoresponse after being exposed to air for three months. Therefore, the controllable atomic doping of BiCuSeO with tunable PTE properties as well as fast and broadband photodetection provides the feasibility for facilitating ongoing research toward PTE devices.