Noninvasive Heart Rate and Respiration Rate Detection Enabled by Perovskite Single Crystal Detector

Abstract The reflectance‐mode photoplethysmography (PPG) technique provides an encouraging platform for heart rate and respiration rate precise monitoring, due to its advantages of the restriction of placed area. The demand for respiration and heart rate monitoring on the reflectance‐mode PPG is lowing baseline drift for accuracy low‐frequency PPG signal detecting from the photodetector. In this study, a surface cleaning‐passivation strategy (SCPS) is developed to simultaneously remove residual solution and suppress the defect on the surface of MAPbBr 3 perovskite single crystals, dramatically reducing trap densities and thus resulting in a high‐quality surface. Photodetector based on the SCPS‐MAPbBr 3 single crystal exhibits a reduced dark current of 2.376 nA at bias of 10 V and a reduced dark current drift from 1.36 × 10 −5 to 6.07 × 10 −7 nA·mm·V −1 ·s −1 at 200 V·cm −1 . A reflectance‐mode PPG monitoring system is built based on the excellent MAPbBr 3 perovskite single crystal photodetector, which is capable to lower baseline drift of PPG waveforms, enabling the accurate low‐frequency signals extraction. This work offers a versatile approach to greatly enhance the performance of MAPbBr 3 single crystal photodetector and highlights the immense potential of the perovskite photodetector for health monitoring technologies by the reflectance‐mode PPG detection system.