skip to main content

Explore Research Products in the NSF-PAR

Title: Broadband infrared photodetection using a narrow bandgap conjugated polymer
Photodetection spanning the short-, mid-, and long-wave infrared (SWIR-LWIR) underpins modern science and technology. Devices using state-of-the-art narrow bandgap semiconductors require complex manufacturing, high costs, and cooling requirements that remain prohibitive for many applications. We report high-performance infrared photodetection from a donor-acceptor conjugated polymer with broadband SWIR-LWIR operation. Electronic correlations within the π-conjugated backbone promote a high-spin ground state, narrow bandgap, long-wavelength absorption, and intrinsic electrical conductivity. These previously unobserved attributes enabled the fabrication of a thin-film photoconductive detector from solution, which demonstrates specific detectivities greater than 2.10 × 10 9 Jones. These room temperature detectivities closely approach those of cooled epitaxial devices. This work provides a fundamentally new platform for broadly applicable, low-cost, ambient temperature infrared optoelectronics.  more » « less
Award ID(s):
1757220
NSF-PAR ID:
10335944
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
Science Advances
Volume:
7
Issue:
24
ISSN:
2375-2548
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ( , Advanced Functional Materials)
    Abstract

    Photodetectors operating across the near‐ to short‐wave infrared (NIR–SWIR,λ= 0.9–1.8 µm) underpin modern science, technology, and society. Organic photodiodes (OPDs) based on bulk‐heterojunction (BHJ) active layers overcome critical manufacturing and operating drawbacks inherent to crystalline inorganic semiconductors, offering the potential for low‐cost, uncooled, mechanically compliant, and ubiquitous infrared technologies. A constraining feature of these narrow bandgap materials systems is the high noise current under an applied bias, resulting in specific detectivities (D*, the figure of merit for detector sensitivity) that are too low for practical utilization. Here, this study demonstrates that incorporating wide‐bandgap insulating polymers within the BHJ suppresses noise by diluting the transport and trapping sites as determined using capacitance‐frequency analysis. The resultingD*of NIR–SWIR OPDs operating from 600–1400 nm under an applied bias of −2 V is improved by two orders of magnitude, from 108to 1010 Jones (cm Hz1/2 W−1), when incorporating polysulfone within the blends. This broadly applicable strategy can reduce noise in IR‐OPDs enabling their practical operation and the realization of emerging technologies.

     
    more » « less
  2. ; ; ; ; ( , Advanced Functional Materials)
    Abstract

    While only few organic photodiodes have photoresponse past 1 µm, novel shortwave infrared (SWIR) polymers are emerging, and a better understanding of the limiting factors in narrow bandgap devices is critically needed to predict and advance performance. Based on state‐of‐the‐art SWIR bulk heterojunction photodiodes, this work demonstrates a model that accounts for the increasing electric‐field dependence of photocurrent in narrow bandgap materials. This physical model offers an expedient method to pinpoint the origins of efficiency losses, by decoupling the exciton dissociation efficiency and charge collection efficiency in photocurrent–voltage measurements. These results from transient photoconductivity measurements indicate that the main loss is due to poor exciton dissociation, particularly significant in photodiodes with low‐energy charge‐transfer states. Direct measurements of the noise components are analyzed to caution against using assumptions that could lead to an overestimation of detectivity. The devices show a peak detectivity of 5 × 1010Jones with a spectral range up to 1.55 µm. The photodiodes are demonstrated to quantify the ethanol–water content in a mixture within 1% accuracy, conveying the potential of organics to enable economical, scalable detectors for SWIR spectroscopy.

     
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al ( , Journal of Vacuum Science & Technology B)

    We experimentally demonstrate a low-cost transfer process of GeSn ribbons to insulating substrates for short-wave infrared (SWIR) sensing/imaging applications. By releasing the original compressive GeSn layer to nearly fully relaxed state GeSn ribbons, the room-temperature spectral response of the photodetector is further extended to 3.2 μm, which can cover the entire SWIR range. Compared with the as-grown GeSn reference photodetectors, the fabricated GeSn ribbon photodetectors have a fivefold improvement in the light-to-dark current ratio, which can improve the detectivity for high-performance photodetection. The transient performance of a GeSn ribbon photodetector is investigated with a rise time of about 40 μs, which exceeds the response time of most GeSn (Ge)-related devices. In addition, this transfer process can be applied on various substrates, making it a versatile technology that can be used for various applications ranging from optoelectronics to large-area electronics. These results provide insightful guidance for the development of low-cost and high-speed SWIR photodetectors based on Sn-containing group IV low-dimensional structures.

     
    more » « less
  4. ; ; ( , Optics Letters)

    We design and characterize compact phase-modulated axilens devices that combine efficient point focusing and grating selectivity within four-level phase mask configurations. Specifically, we select and characterize in detail two device configurations designed for long-wavelength infrared (LWIR) operation in the6µ<#comment/>m−<#comment/>12µ<#comment/>mwavelength range. These devices are ideally suited for monolithic integration atop the substrate layers of infrared focal plane arrays (IR-FPAs) for use in multiband LWIR photodetection. We systematically study their focusing efficiency, spectral response, and crosstalk ratio, and we demonstrate a single-component microspectrometer. Our design method leverages the Rayleigh–Sommerfeld (RS) diffraction theory that is validated numerically using the finite element method (FEM). The proposed devices are broadband and polarization insensitive and add fundamental spectroscopic capabilities to miniaturized optical components for a number of applications in LWIR detection and spectroscopy.

     
    more » « less
  5. ( , Proceedings SPIE)
    Rau, Ileana ; Sugihara, Okihiro ; Shensky, William M (Ed.)
    Low-energy, infrared (IR) photodetection forms the foundation for industrial, scientific, energy, medical, and defense applications. State-of-the-art technologies suffer from limited modularity, intrinsic fragility, high-power consumption, require cooling, and are largely incompatible with integrated circuit technologies. Conjugated polymers offer low-cost and scalable fabrication, solution processability, room temperature operation, and other attributes that are not available using current technologies. Here, we demonstrate new materials and device paradigms that enable an understanding of emergent light-matter interactions and optical to electrical transduction of IR light. Photodiodes show a response to 2.0 μm, while photoconductors respond across the near- to long-wave infrared (1–14 µm). Fundamental investigations of polymer and device physics have resulted in improving performance to levels now matching commercial inorganic detectors. This is the longest wavelength light detected for organic materials and the performance exceeds graphene at longer wavelengths. Photoconductors outperform their inorganic counterparts and operate at room temperature with higher response speeds. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email