The integration of organic materials with colloidal quantum dots (QDs) has the merits the advantages of the molecular diversity and photoelectric tunability for ultrasensitive photodetector applications. Herein, a uniform CsPbBr QD layer is sandwiched between the same poly-(N, N′-bis-4-butylphenyl-N, N′-bisphenyl) benzidine (Poly-TPD) and phenyl-C61-butyric acid methyl ester (PCBM) (1:1) organic blend films. The CsPbBr QD layer efficiently absorbs the excitation light, where the generated exciton can sufficiently diffuse to the interface of QD and organic blend layers for efficient charge separation and effective gate modulation. Owing to the desirable heterojunction at the interface, the dark current is substantially suppressed, while the photocurrent is increased in comparison with those of pristine QDs photodetectors. The ultrafast charge transfer time (≈300 ps) from QDs to organic blend layer measured by the time-resolved transient absorption spectroscopy is potentially benefit the enhanced electron–hole pair dissociation. The solution-processed, organic (Poly-TPD:PCBM blend)-modulated CsPbBr QDs photodetector are exhibited ultrasensitive photoresponse abilities in terms of in terms of noise equivalent power (NEP = 1 × 10 W Hz), I/I ratio (2 × 10), and the a specific detectivity (D* = 4.6 × 10 Jones). The results will be a starting point for ultrasensitive next-generation light detection technologies.