用于PPG信号测试的大面积柔性胶体量子点红外光电二极管

Large-area flexible colloidal-quantum-dot infrared photodiodes for photoplethysmogram signal measurements

以铟镓砷、碲镉汞等外延生长的单晶材料作为吸光层的光电二极管是红外探测技术的主流方案.然而,它们的刚性结构、极高成本以及有限尺寸使其无法满足诸如人体内外环境监测,便携式医疗等智能穿戴应用的需求.基于低温液相工艺的胶体量子点(CQDs)红外光电二极管是实现大面积柔性红外光电探测器极具竞争力的候选方案,但由于其发展年限较短,仍存在暗电流密度大、均匀性差以及工作稳定性差等问题.本文通过在CQDs墨水中引入聚酰亚胺来制备CQDs光电二极管.这种聚合物配体既实现了对CQDs表面缺陷态的钝化,又能够保持胶体墨水的单分散性和持久性.这两点使得光电探测器的吸光层形貌得以改善,同时暗电流密度显著降低,极大地优化了CQDs光电二极管的均匀性和工作稳定性.采用该方案制备的大面积柔性CQDs光电二极管能够实现高于10^(13)Jones的比探测率,可在环境光下实现可穿戴式光电体积描记(PPG)心率信号监测,极大地降低了成本和功耗.

Epitaxially grown photodiodes are the foundation of infrared photodetection technology;however,their rigid structure and limited area scaling limit their use in advanced applications.Colloidal-quantum-dot(CQD)infrared photodiodes have increased active areas through solution processing,and are thus potential candidates for large-area flexible photodetection,but these large-area photodiodes have disadvantages such as large dark current density,poor homogeneity,and poor stability.Therefore,this study established a fabrication strategy for large-area flexible CQD photodiodes that involves introducing polyimide to CQD ink to improve CQD passivation,monodisperse ink persistence,and film morphology.The resulting CQD photodiodes exhibited reduced dark current density and improved homogeneity and work stability.Furthermore,the as-prepared photodiodes exhibited a detectivity(D^(*))of greater than 1013 Jones,which was higher than other reported CQD photodetectors.The CQD photodiodes developed in this study can be used for wearable photoplethysmogram(PPG)signal measurement under ambient light at reduced cost and power consumption.