We report all solid-state nanostructured inorganic−organic heterojunction solar cells fabricated by depositing Sb2S3 and poly(3-hexylthiophene) (P3HT) on the surface of a mesoporous TiO2 layer, where Sb2S3 acts as an absorbing semiconductor and P3HT acts as both a hole conductor and light absorber. These inorganic−organic light harvesters perform remarkably well with a maximum incident-photon-to-current efficiency (IPCE) of 80% and power conversion efficiency of 5.13% under air-mass 1.5 global (AM 1.5G) illumination with the intensity of 100 mW cm−2. These devices are highly stable under room light in air, even without encapsulation. The present findings offer novel directions for achieving high-efficiency solid-state solar cells by hybridization of inorganic−organic light harvesters and hole transporters.