Toward Broadband Imaging: Surface-Engineered PbS Quantum Dot/Perovskite Composite Integrated Ultrasensitive Photodetectors

PbS colloidal quantum dots passivated by the thiocyanate anion (SCN–) are developed to combine with perovskite (CH3NH3PbI3) as building blocks for UV–vis–NIR broadband photodetectors. Both high electrical conductivity and appropriate energy-level alignment are obtained by the in situ ligand exchange with SCN–. The PbS-SCN/CH3NH3PbI3 composite photodetectors are sensitive to a broad wavelength range covering the UV–vis–NIR region (365–1550 nm), possessing an excellent responsivity of 255 A W–1 at 365 nm and 1.58 A W–1 at 940 nm, remarkably high detectivity of 4.9 × 1013 Jones at 365 nm and 3.0 × 1011 Jones at 940 nm, and fast response time of ≤42 ms. Furthermore, a 10 × 10 photodetector array is fabricated and integrated, which constitutes a high-performance broadband image sensor. Our approach paves a way for the development of highly sensitive broadband photodetectors/imagers that can be easily integrated.