Overcoming\nthe EQE × Li-Fi Frequency Constraint\nby Modulating the PbS CQDs Distribution in Perovskite Film

Advanced photodetectors are crucial for high-fidelity\noptical communication.\nHowever, the tradeoff between high external quantum efficiency (EQE)\nand high light fidelity (Li-Fi) frequency often limits data transmission\naccuracy and timeliness. Here, we report a photodetector consisting\nof lead sulfide (PbS) colloidal quantum dots (CQDs) with near-infrared\nresponsiveness and perovskite frameworks responsible for the charge\ntransport to overcome the EQE × Li-Fi constraint. Optimizing\nthe PbS CQDs distribution and trap depth in the perovskite layer enhances\ncharge injection, achieving a device gain of 11892% for 1200 nm photons\nand a response frequency of 24 kHz at −2 V. The device exhibits\na record EQE × Li-Fi frequency product of 10<sup>6</sup> Hz.\nWe have applied the detector to near-infrared optical communications\nat a data transfer rate of 2000 bits per second (2 kbps) to demonstrate\nthe advances in high fidelity, the device retains over 98% of the\noriginal waveform information in its output.