Spectral-selective light detection and ranging at 1550 nm using tandem colloidal quantum dot photodiodes.

Light detection and ranging (LiDAR) systems enable three-dimensional (3D) imaging for emerging applications in autonomous driving and mixed reality. The operational wavelength of LiDAR detectors is transitioning from 905 nm to 1550 nm, leveraging the higher safety power threshold and superior coherence of 1550 nm lasers. Colloidal quantum dots (CQDs) photodiodes have shown good performance and low cost for two-dimensional (2D) imaging covering 1550 nm, however, been faced two main challenges, including poor spectral selectivity and slow response speed as a LiDAR detector. Here, we introduce a tandem PbSe CQDs photodiode that functions as an integrated photonic-electronic link, overcoming both challenges by synergistically merging optical pre-processing and electronic post-processing within a single structure. The designed tandem structure leverages a synergistic combination of RC time constant suppression and charge collection narrowing, yielding a record-fast response time of 1.01 ns among the reported CQD devices and a 13-fold suppressed external quantum efficiency (EQE) in the visible range compared to single-junction devices. We further showcase a spectral-selective LiDAR operating at 1550 nm using the tandem CQDs photodiodes, achieving a centimeter-level spatial resolution while maintaining 97.9% of the signal-to-noise ratio under strong background interference.