| PbS CQDs are becoming a hot research topic for the next generation of short-wave infrared image sensors due to their tunable absorption spectra in the short-wave infrared range,as well as their optoelectronic properties such as doping type and concentration.In addition,they can be directly heterogeneously integrated with silicon-based CMOS readout circuits through low-temperature solution methods.Passive pixel structures,due to their simple device structure and fabrication process,are expected to be used to construct low-cost and high-performance quantum dot infrared imaging arrays.However,the problem of electrical crosstalk between pixels under illumination and high static power consumption make it difficult to achieve high-quality image recognition.This article focuses on how to construct passive imaging arrays using PbS CQDs,with the aim of solving the problems of electrical crosstalk and high static power consumption of devices under illumination in passive matrix.From the perspective of device performance optimization and pixel structure design,the study explores the modulation effect of the electron-blocking layer on the reverse bias dark current,and designs a "PbS CQDs photodiode-organic rectifier diode" pixel structure with reverse vertical integration,which effectively suppresses electrical crosstalk and static power consumption.The feasibility of the pixel structure in large-scale passive imaging arrays are demonstrated through imaging results in the visible to short-wave infrared range.The specific research content are as follows:(1)Starting from the basic structure of an ITO/PEIE/ZnO/PbS/MoO3/Ag nip-type photodiode,this paper analyzes the separation and transport mechanism of photogenerated carriers in the heterojunction.By introducing different electron blocking layers to increase the potential barrier for reverse electron injection,the reverse bias dark current is effectively suppressed.In addition,the Poly-TPD electron blocking layer/PbS CQDs active layer interface provides the largest potential barrier,effectively reducing the contribution of interface thermal charges to the dark current.At a bias voltage of-1.5 V,a steady-state dark current density as low as 1.51 ×10-7 A/cm2 is obtained.Meanwhile,this paper replaces chlorobenzene with 1,2-dichlorobenzene as the solvent for Poly-TPD,which improves the morphology and conductivity of the polymer film,reduces the series resistance of the device without sacrificing the reverse bias dark current,and significantly increases the forward current.A high-performance photodiode with high photoresponse and ultra-high rectification ratio(～1.49×106)is obtained.(2)To address the problems of electrical crosstalk and high standby power consumption under illumination in passive imaging arrays,this paper designs and implements a reverse vertically integrated "photodiode-organic rectifier diode" pixel structure,and each pixel consists of a "back-to-back" vertical stack of PbS CQDs photodiodes and a P3HT rectifier diodes.The difference in the work functions of the positive and negative electrodes results in P3HT energy level bending,which creates a charge blocking barrier that cuts off the transmission path of photo-generated holes at zero bias and forward bias.Conversely,under reverse bias,the band bending direction changes,which is conducive to the transmission and extraction of photo-generated holes.Therefore,this structure effectively suppresses the electrical crosstalk in passive matrix and ensures low standby power consumption of the devices.When a bias of-2 V was applied,the single-pixel device based on this pixel structure achieves a responsivity of 0.135 A W-1 and a detectivity of 6.10×1011 Jones at a wavelength of 1413 nm.Subsequently,an 8×8 passive imaging array was designed and fabricated,and a signal processing circuit and imaging system were designed and built to achieve accurate image recognition in the visible-shortwave infrared band. |
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