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.