In this study, we report solution-processed photodetectors fabricated by methylammonium triiodide perovskite (CH₃NH₃PbI₃) incorporated with PbS quantum dots (QDs) through the trap-assisted charge-injection effect. In order to increase the photo-responsivity by eliminating the charge injection barrier from the cathode electrode, PbS QDs, which possesses large amount of trap states, are introduced into the CH₃NH₃PbI₃ thin film for establishing ohmic contact at the CH₃NH₃PbI₃/aluminum (Al) interface. As a result, an external quantum efficiency of ~4500%, a photoresponsivity of ~15,000 mA/W and a detectivity of over 6×10¹³ Jones (1 Jones=1 cmHz^1/2 W⁻¹) at a small bias of 2 V, and a photoresponse time of 11.5 µs are observed from the solution-processed photodetectors fabricated by the CH₃NH₃PbI₃:PbS QDs nanocomposites thin film.