Ag₂Se-based thermoelectric films and devices have become a popular research topic in the field of wearable thermoelectric energy conversion due to their narrow bandgap semiconductor properties, which exhibit good thermoelectric properties at room temperature. These films are typically constructed by stacking nanoparticles, and the dimensions of nanomaterials significantly impact the thermoelectric transport properties of the network. In this study, Ag₂Se nanomaterials with different dimensions were prepared by solvothermal and template methods, and flexible Ag₂Se thermoelectric films were constructed on polyimide substrates using Ag₂Se nanomaterials with different dimensions by spraying process combined with high-temperature post processing. The effects of the dimensionality of Ag₂Se nanomaterials on the microstructures and thermoelectric properties of the films were then systematically investigated. Zero dimensional Ag₂Se nanoparticles exhibited superior conductive networks and thermoelectric properties in comparison to one dimensional nanowire structures. Furthermore, the room temperature power factor of the films reached 199.6 μW·m^-1·K^-2, and the power factor was 257.9 μW·m^-1·K^-2 at the temperature of 375 K, which indicated the good thermoelectric properties of the films. Additionally a device was designed and integrated based on the Ag₂Se films, with four thermoelectric arms and excellent performance. The device exhibited good mechanical flexibility and output performance with internal resistance increased by only 8.2% after 1000 bending cycles (bending radius: 20 mm), and the device displayed an open-circuit voltage of 9.1 mV and a max output power of 43.7 nW at a temperature difference of 30 K. This study presents a novel approach for the preparation of flexible Ag₂Se-based thermoelectric thin-film materials and devices.