In this contribution, we report a novel pyridinium-pended conjugated polyelectrolyte (DPTFBr) for application in photocatalytic hydrogen evolution and organic solar cells. DPTFBr contains pyridinium salts attached to its backbone, which enable its transition from the pristine state to a radical state in the presence of amines and under illumination via a photo-induced amine doping process. The transition results in apparent shifts in the UV-vis absorption spectrum, electrochemical redox potential, and electron spin resonance of the resulting polymer. The unique properties of DPTFBr facilitate its application in photocatalytic hydrogen evolution with a high photocatalytic hydrogen evolution rate of 7.33 mmol g⁻¹ h⁻¹, which is 63- and 12-fold higher than those of its neutral and oxidized analogues, respectively. Additionally, the excellent interface modification capabilities of the pyridinium side chains in DPTFBr enable efficient electron transport/collection, thus giving rise to high-performance organic solar cells with a power conversion efficiency of over 16%.