<p>Control of carrier polarity in two-dimensional van der Waals semiconductors is essential for integrated electronic and optoelectronic systems. Here, we demonstrate that substitutional vanadium doping enables robust p-type modulation in multilayer WSe₂ with pronounced thickness-dependent transport behavior. The transfer curve of V-doped transistor reveals that increasing vanadium concentration progressively enhances hole-dominant transport, in contrast to pristine WSe₂, which evolves toward ambipolar and n-type conduction with increasing thickness. Leveraging this thickness-engineered of WSe₂/V-WSe₂ platform, we demonstrate three distinct device architectures: (i) Complementary logic inverters, (ii) flexible photovoltaic devices, and (iii) gate-programmable in-sensor imaging devices. Flexible photovoltaic homojunctions exhibit a fast response time of 1.36 µs, broadband photodetection spanning the ultraviolet to near-infrared, and a high external quantum efficiency of up to 51.3%, while maintaining stable performance under mechanical deformation. Separately, complementary inverter devices demonstrate reliable logic functionality, whereas gate-tunable homojunctions reversibly switch between negative and positive photocurrent through gate-modulated band alignment, enabling programmable in-sensor image processing. Our results establish vanadium doping as an effective strategy for carrier polarity control and for high-performance WSe₂/V-WSe₂-based homojunction electronic and optoelectronic devices.</p><p></p>