Emerging Design and Characterization Guidelines for Polymer-Based Infrared Photodetectors

Abstract

CONSPECTUS: Infrared photodetectors are essential to many applications, including surveillance, communications, process monitoring, and biological imaging. The short-wave infrared (SWIR) spectral region (λ = 1−3 μm) is particularly powerful for health monitoring and medical diagnostics because biological tissues show low absorbance and minimal SWIR autofluorescence, enabling greater penetration depth and improved resolution in comparison with visible light. However, current SWIR photodetection technologies are largely based on epitaxially grown inorganic semiconductors, which are costly, require complex processing, and impose cooling requirements incompatible with wearable electronics. Solution-processable semiconductors are being developed for infrared detectors to enable low-cost direct deposition and facilitate monolithic integration and resolution not achievable using current technologies. In particular, organic semiconductors offer numerous advantages, including large-area and conformal coverage, temperature insensitivity, and biocompatibility, for enabling ubiquitous SWIR optoelectronics. This Account introduces recent efforts to advance the spectral response of organic photodetectors into the SWIR. High-performance visible to near-infrared (NIR) organic photodetectors have been demonstrated by leveraging the wealth of knowledge from organic solar cell research in the past decade. On the other hand, organic semiconductors that absorb in the SWIR are just emerging, and only a few organic materials have been reported that exhibit photocurrent past 1 μm. In this Account, we survey novel SWIR molecules and polymers and discuss the main bottlenecks associated with charge recombination and trapping, which are more challenging to address in narrow-band-gap photodetectors in comparison with devices operating in the visible to NIR. As we call attention to discrepancies in the literature regarding performance metrics, we share our perspective on potential pitfalls that may lead to overestimated values, with particular attention to the detectivity (signal-to-noise ratio) and temporal characteristics, in order to ensure a fair comparison of device performance. As progress is made toward overcoming challenges associated with losses due to recombination and increasing noise at progressively narrower band gaps, the performance of organic SWIR photodetectors is steadily rising, with detectivity exceeding 10 11 Jones, comparable to that of commercial germanium photodiodes. Organic SWIR photodetectors can be incorporated into wearable physiological monitors and SWIR spectroscopic imagers that enable compositional analysis. A wide range of potential applications include food and water quality monitoring, medical and biological studies, industrial process inspection, and environmental surveillance. There are exciting opportunities for low-cost organic SWIR technologies to be as widely deployable and affordable as today's ubiquitous cell phone cameras operating in the visible, which will serve as an empowering tool for users to...

Solution-Processed Phototransistors Combining Organic Absorber and Charge Transporting Oxide for Visible to Infrared Light Detection

“…For comparison, infrared photodiodes operating without an external bias are dominated by thermal noise. 5 However, here, the devices are under bias, and shot noise or flicker noise can overtake the thermal noise component depending on the operational bias and frequency. The measured noise in the accumulation regime (V GS = 0 V) is almost two orders of magnitude higher than in the depletion regime (V GS = −10 V), as shot noise 35 is proportional to the square root of current density.…”

“…This novel IR phototransistor design is shown to exceed the performance of commercial vacuum-processed germanium photodiodes at video rate spanning the visible to the shortwave IR (500 < λ < 1300 nm) under low light illumination. Figure 1a shows the chemical structures of the materials in the BHJ layer, which includes a blend of a narrow band-gap IR absorbing polymer (poly(4-(5-(4-(3,5-bis(dodecyloxy)benzylidene)-4H-cyclopenta[2,1-b:3,4-b′]dithiophen-2-yl)thiophen-2-yl)-6,7-dioctyl-9-(thiophen-2-yl)- [1,2,5]thiadiazolo[3,4-g]quinoxaline)) as the donor 26 and [6,6]phenyl-C 71 -butyric acid methyl ester (PC 71 BM) as the acceptor. The donor-to-acceptor ratio is 1:2 by weight, and devices are fabricated with or without camphor as the highpermittivity additive.…”

Organic‐Inorganic Hybrid Perovskite Single Crystals: Crystallization, Molecular Structures, and Bandgap Engineering

“…[127] Since the photodetection relies on the bandgap of materials, organic-inorganic hybrid perovskite indicates the ability of materials for transducing photons of different energies into electrical signals, which can be used for subsequent processing, image reconstruction and storage. [126][127][128][129] Therefore, organic-inorganic hybrid perovskites provide the possibilities to design novel photodetectors for commercial applications.…”

Near-infrared emissive carbon dots with 33.96% emission in aqueous solution for cellular sensing and light-emitting diodes

“…The development of more environmentally friendly synthesis methods for the efficient and controllable preparation of red-emitting CDs with high quantum yields in aqueous solutions is crucial [19][20][21]. Red fluorescence emitting materials are favorable for many applications, particularly in the biomedical fields, because blue light and ultraviolet light usually cause damage to biological tissues [22,23]. Since the discovery of CDs, researchers have explored a variety of synthesis pathways to prepare CDs from a variety of carbon sources, such as arc discharge, laser ablation [24,25], electrochemical synthesis [26,27], microwave [28,29], acidic oxidation, solvothermal methods [30,31], and hydrothermal methods [32][33][34][35].…”