Optical Distance Measurement Based on Induced Nonlinear Photoresponse of High-Performance Organic Near-Infrared Photodetectors

Abstract

Extraction barriers are usually undesired in organic semiconductor devices since they lead to reduced device performance. In this work, we intentionally introduce an extraction barrier for holes, leading to nonlinear photoresponse. The effect is utilized in near-infrared (NIR) organic photodetectors (OPDs) to perform distance measurements, as delineated in the focus-induced photoresponse technique (FIP). The extraction barrier is introduced by inserting an anodic interlayer with deeper highest occupied molecular orbital (HOMO), compared to the donor material, into a well-performing OPD. With increasing irradiance, achieved by decreasing the illumination spot area on the OPD, a higher number of holes pile up at the anode, counteracting the built-in field and increasing charge-carrier recombination in the bulk. This intended nonlinear response of the photocurrent to the irradiance allows determining the distance between the OPD and the light source. We demonstrate fully vacuum-deposited organic NIR optical distance photodetectors with a detection area up to 256 mm 2 and detection wavelengths at 850 and 1060 nm. Such NIR OPDs have a high potential for precise, robust, low-cost, and simple optical distance measurement setups.

High‐speed focus‐induced photoresponse in amorphous silicon photodetectors for optical distance measurements

“…In this work, the non‐linear current breakdown can clearly be verified up to an electrical bandwidth of at least 3.5 MHz (Figure 5c) that is 175 times higher than the best reported value in [9]. Since the achievable bandwidth depends on a variety of parameters, for example, the detector area, the light‐absorbing material composition and thickness, defect densities, contact resistances, the device architecture itself and so forth, we expect significant improvements in the future with bandwidth optimized designs.…”

“…Although state-of-the-art FIP sensors combine several highly attractive advantages, comparatively low cut-off frequencies stagnate at very low bandwidths, severely restricting their widespread application. This restriction stems from photodetector technologies based on high defect densities and low charge carrier mobility materials, preventing a fast optical distance acquisition above 20 kHz [5,8,9]. Here, we present FIP detector technologies based on amorphous silicon that resolve such bandwidth limitations and expand photodetector speed by more than two orders of magnitude utilizing just one single-pixel photodetector.…”

High-speed nonlinear focus-induced photoresponse in amorphous silicon photodetectors for ultrasensitive 3D imaging applications

“…Compared to previous reports, we propose an alternative FIP sensor readout to extract ultrasensitive distance information instantaneously from the incident light by applying a Fast Fourier Transform (FFT) on the sensor output at different distances. This novel approach based on a harmonic analysis allows for single-pixel distance determination, whereas previous concepts invariably relied on two separate FIP sensors and a signal comparison of two detector outputs 13 , 14 , 18 . The proposed sensor readout in this work can easily be integrated on-chip, e.g.…”

“…Although the FIP technique combines several advantages, its true benefit can only be achieved at high frequencies which enables the observation of fast moving objects and significantly reduces flicker noise, hence increasing the signal-to-noise ratio (SNR). Unfortunately, the cut-off frequency of state of the art sensors is presently limited to a few 18 , only.…”

“…PbS photoconductors are opaque prohibiting large-scale integration as single pixel sensor stacks. The organic photodetectors (OPD) proposed in 18 also require an additional passivation and utilize a complex multilayer structure to form internal energetic barriers that screen the electric field for different irradiances causing the FIP.…”