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.