Poly(3,4-ethylenedioxy thiophene):poly(styrenesulfonate) (PEDOT:PSS) exhibits valuable characteristics concerning stability, green-processing, flexibility, high electrical conductivity, and ease of property modulation, qualifying it as one of the most promising p-type organic conductors for thermoelectric (TE) applications. While blending with inorganic counterparts is considered a good strategy to further improve polymeric TE properties, only a few attempts succeed so far due to inhomogeneous embedding and the non-ideal organic-inorganic contact. Here a new strategy to include nanoparticles (NPs) without any ligand termination inside PEDOT:PSS thin films is proposed. Spark discharge-generated tin oxide NPs (SnOx-NPs) are "gently" and homogenously deposited through low-energy diffusion mode. Strong interaction between naked SnOx-NPs and PSS chains occurs in the topmost layer, causing a structural reorganization towards an improved PEDOT chains crystalline packing at the bottom, providing a positive contribution to the electrical conductivity. Meanwhile, dedoping and energy filtering effect introduced by the SnOx-NPs cause dramatic Seebeck coefficient enhancement. The optimized power factor of 116 mu Wm(-1) K-2 achieved is more than six times higher than the value found for the film without NPs. This easy and efficient strategy promises well for future mass production of flexible TE devices and the mechanism revealed may inspire future research on TEs and flexible electronics.