Inorganic Photodetectors Research Articles

Fabrication of hybrid organic and inorganic photodetector

Fabrication of hybrid organic and inorganic photodetector

Development of high-performance flexible photodetectors through band engineering and synergistic modulation in P3HT/C3N5 thin film

Flexible photodetectors, with applications ranging from large-scale photosensors to flexible solar cells and fiber-optical sensors, offer a promising avenue for technological advancement. Despite their high performance and stability, conventional inorganic photodetectors suffer from complex, costly manufacturing processes and lack mechanical flexibility. This gap is potentially bridged by organic semiconducting polymers (OSPs), which require enhancements in charge transport capabilities. Integrating exfoliated graphitic carbon nitride (C3N5) with OSPs, specifically into a poly(3-hexylthiophene-2,5-diyl) (P3HT) matrix, has shown to significantly improve electrical and optoelectronic properties due to C3N5's excellent optoelectronic features, adjustable bandgap, and stability. This study successfully fabricated flexible photodetectors with a P3HT/C3N5(3 %) mix in a Schottky barrier diodes (SBDs) configuration, achieving a 100-fold increase in photocurrent, exceptional flexibility, and rapid response to light. These findings highlight the potential of a synergistic approach in developing high-performance, commercially viable flexible photodetectors.

Machine learning-assisted chemical space generation of small molecule organic semiconductors for efficient photodetectors

Organic photodetectors (OPDs), the emerging next-generation candidates for light sensing applications, could compensate deficiencies of the traditional inorganic photodetectors. To get OPDs of highly improved performance, and broader applications, machine learning (ML) technique is employed. A chemical space of 20,000 organic semiconductors (OSCs) by RDKit via BRICKS (Breaking Retrosynthetically Interesting Chemical Substructures) method was achieved, from the selected building blocks of the OSC data obtained from the literature, contributing to big data. Out of these, top twenty OSCs were screened based on synthetic accessibility score, chemical similarity analysis, and structural behavior understanding.

Semitransparent Near‐Infrared Organic Photodetectors: Flexible, Large‐Area, and Physical‐Vapor‐Deposited for Versatile Advanced Optical Applications

AbstractOrganic photodetectors (OPDs) have experienced remarkable performance improvements over the past decade thanks to significant advancements in organic material synthesis and device architecture engineering. In this study, high‐performance near‐infrared (NIR) OPDs with versatile advanced properties, including large detection areas, mechanical flexibility, and high transparency are realized. By incorporating a thin photo‐absorbing layer, functional blocking layers with a large energy gap, and semitransparent electrodes, the OPDs achieve an average visible transmittance (AVT) of up to 53.4% and color rendering index (CRI) of up to 95 within the human vision photopic response window of 380–780 nm. Both the small (6.44 mm2) and large (256 mm2) detection‐area semitransparent OPDs demonstrate an impressive external quantum efficiency (EQE) of 34% and 36%, and specific detectivity (D*) of 1.4 × 1013 and 1.1 × 1012 Jones, respectively, comparable to silicon‐based inorganic photodetectors. As application demonstrations, OPDs with rigid and flexible substrates are employed for NIR imaging and biosensing, respectively. Notably, the flexible semitransparent OPDs are utilized as signal receivers in conjunction with semitransparent NIR organic light‐emitting diodes (OLEDs) operating as signal producers, demonstrating the feasibility of invisible optical communication. These OPDs represent the best‐performing see‐through devices with flexibility, making them promising candidates for integratable, bio‐compatible, and invisible optical‐sensing applications.

Synergistic nucleation regulation using 4,4',4''-tris(carbazol-9-yl)-triphenylamine and moisture for stably air-processed high-performance perovskite photodetectors.

Perovskite photodetectors (PPDs) offer a promising solution with low cost and high responsivity, addressing the limitations of traditional inorganic photodetectors. However, there is still room for improvement in terms of the dark current and stability of air-processed PPDs. In this study, 4,4',4''-tris(carbazol-9-yl)-triphenylamine (TCTA) was utilized as a nucleation agent to enhance the quality of perovskite films. The synergistic effect of TCTA and moisture promotes rapid nucleation of PbI2-PbCl2, resulting in an increased nucleation rate and the elimination of pinholes in the film. By employing additive engineering, we obtained a PbI2-PbCl2 layer with high coverage, leading to a low density of traps in the corresponding perovskite film. Consequently, the modified PPD exhibits a remarkable reduction in dark current density by over one order of magnitude, reaching 2.4 × 10-10 A cm-2 at -10 mV, along with a large linear dynamic range (LDR) of 183 dB. Furthermore, the resulting PPD demonstrates remarkable stability, retaining 90% of the initial external quantum efficiency (EQE) value even after continuous operation for over 3200 hours. Owing to a fast response time in the nanosecond range, the PPD could convert modulated light signals into electrical signals at a speed of 588 Kbit s-1, highlighting the great potential in the field of optical communication.

High‐Performing Acid‐Free PEDOT:PSS‐Based Organic Photodiodes for Cardiovascular Disease Diagnosis

AbstractPhotodetectors made from low‐toxicity organic materials are considered a promising alternative to conventional inorganic photodetectors. However, the performance of current organic photodetectors (OPD) needs to be further enhanced. This study aims to introduce acid‐free poly(3,4‐ethylenedioxythiophene)‐(polystyrene sulfonate) (PEDOT‐(PSS)) films in order to improve the performance of OPDs in practical applications. Utilization of heterocyclic 1,3‐diazole (HDZ) in PEDOT‐(PSS) improves the polymerization degree, carrier mobility, and other physicochemical properties. These enhanced properties also improve the comprehensive performance of OPD. In this flow, the enhanced noise suppression is also confirmed by elucidating the device's performance limitations. Consequently, the presented OPD‐based photoplethysmography sensor has the ability to diagnose blood circulation status and cardiovascular diseases. This accomplishment marks the first in single pixel‐based organic photodiode research.

Advances in Polymethine Dyes for Near‐Infrared Organic Photodiodes†

Comprehensive SummaryNear‐infrared organic photodiodes (NIR OPDs) have tremendous potential in industrial, military, and scientific applications, due to their unique features of lightweight, low toxicity, high structural flexibility, cooling‐system‐free, etc. However, the overall performance of currently available NIR OPDs still lags behind the commercial inorganic photodetectors, ascribed to the critical challenge of realizing organic semiconductors with sufficiently low optical bandgap and excellent optoelectronic properties simultaneously. Among various types of NIR‐absorbing organic semiconductors, polymethine dyes not only possess advantages of simple synthesis and structural diversity, but also show fascinating optical and aggregation features in the solid state, making them attractive material candidates for NIR OPDs. In this review, after a brief introduction of NIR OPDs and polymethine dyes, we comprehensively summarize the advances of polymethine dyes for broadband and narrowband NIR OPDs, and further introduce their applications in all‐organic optical upconversion devices and photoplethysmography sensors. In particular, the relationship between the chemical structure and the aggregation behaviors of polymethine dyes and the device performance is carefully discussed, providing some important molecular insights for developing high performance NIR OPDs.

Recent Progress on OrganicNear‐InfraredPhotodetectors: Mechanism, Devices, and Applications†

Comprehensive SummaryNear infrared light organic photodetectors have attracted tremendous attention due to their tailorable response, ease of processing, compatibility with flexible substrate, room temperature operation and broad applications such as remote sensing, health monitoring, artificial vision, night vision, and so on. Recently, the great improvement obtained on the important figures of merit performances has made organic photodetectors catch up and even surpass those of inorganic photodetectors in some respects. In this review, after a brief illustration of the organic photodetectors' figures of merit performances, we summarize the research progress of panchromatic and narrowband near infrared light organic photodetectors from their working mechanism, strategies to achieve narrowband near infrared light organic photodetectors, to some practical applications. Finally, we discuss the development challenge of the near infrared light organic photodetectors.

Highly Efficient and Stable Self-Powered Mixed Tin-Lead Perovskite Photodetector Used in Remote Wearable Health Monitoring Technology.

Realization of remote wearable health monitoring (RWHM) technology for the flexible photodiodes is highly desirable in remote-sensing healthcare systems used in space stations, oceans, and forecasting warning, which demands high external quantum efficiency (EQE) and detectivity in NIR region. Traditional inorganic photodetectors (PDs) are mechanically rigid and expensive while the widely reported solution-processed mixed tin-lead (MSP) perovskite photodetectors (PPDs) exhibit a trade-off between EQE and detectivity in the NIR region. Herein, a novel functional passivating antioxidant (FPA) strategy has been introduced for the first time to simultaneously improve crystallization, restrain Sn2+ oxidization, and reduce defects in MSP perovskite films by multiple interactions between thiophene-2-carbohydrazide (TAH) molecules and cations/anions in MSP perovskite. The resultant solution-processed rigid mixed Sn-Pb PPD simultaneously achieves high EQE (75.4% at 840 nm), detectivity (1.8 × 1012 Jones at 840 nm), ultrafast response time (trise /tfall = 94 ns/97 ns), and improved stability. This work also highlights the demonstration of the first flexible photodiode using MSP perovskite and FPA strategy with remarkably high EQE (75% at 840 nm), and operational stability. Most importantly, the RWHM is implemented for the first time in the PIN MSP perovskite photodiodes to remotely monitor the heart rate of humans at rest and after-run conditions.

Enhancing Transition Dipole Moments of Heterocyclic Semiconductors via Rational Nitrogen-Substitution for Sensitive Near Infrared Detection.

Designing ultrastrong near-infrared (NIR) absorbing organic semiconductors is a critical prerequisite for sensitive NIR thin film organic photodetectors (OPDs), especially in the region of beyond 900nm, where the absorption coefficient of commercial single crystalline silicon (c-Si) is below 103 cm-1 . Herein, a pyrrolo[3,2-b]thieno[2,3-d]pyrrole heterocyclic core (named as BPPT) with strong electron-donating property and stretched geometry is developed. Relative to their analogue Y6, BPPT-contained molecules, BPPT-4F and BPPT-4Cl, show substantially upshifted and more delocalized highest occupied molecular orbitals, and larger transition dipole moments, leading to bathochromic and hyperchromic absorption spectra extending beyond 1000nm with very large absorption coefficients (up to 3.7-4.3 × 105 cm-1 ) as thin films. These values are much higher than those (104 to 1 × 105 cm-1 ) of typical organic semiconductors, and 1-2 orders higher than those of commercial inorganic materials, such as c-Si, Ge, and InGaAs. The OPDs based on BPPT-4F or BPPT-4Cl blending polymer PBDB-T show high detectivity of above 1012 Jones in a wide wavelength range of 310-1010nm with excellent peak values of 1.3-2.2 × 1013 Jones, respectively, which are comparable with and even better than those commercial inorganic photodetectors.

Synthesis of Colloidal CsHgI3 Nanocrystals by Laser Ablation in Liquid for Organic–Inorganic Photodetectors

Synthesis of Colloidal CsHgI3 Nanocrystals by Laser Ablation in Liquid for Organic–Inorganic Photodetectors

Progress in Organic Photodiodes through Physical Process Insights

Photodetectors based on organic materials have enormous potential due to their attractive optoelectronic and mechanical properties. In recent years, some of the performance metrics comparable to the conventional inorganic photodetectors have been realized in visible‐range organic photodiodes (OPDs). These advancements in OPDs are mainly driven by innovations in device engineering and material design. However, insights into the fundamental performance limiting factors are imperative to further understand, optimize, and predict the performance metrics of OPD devices beyond conventional wisdom. In this review, the major progress in understandings related to trap state, charge transfer state, and noise/detectivity limits in OPD devices are highlighted.

Ultrasonic irradiation assisted growth of organic polypyrrole nanospheres reinforced 3D-hierarchical macroporous Ni-foam based high performance broadband photodetector

Most inorganic photodetectors are rigid and have narrow intrinsic bandgap, which severely limits their application in next generation flexible electronics. To overcome this issue, this work reports a flexible, biocompatible, organic-photodetector based on solution processed Ppy nanospheres deposited over 3D-hierarchical macro-porous Ni foam substrate using ultrasonic irradiation technique. The Ni foam substrate is used as buffering layer to bond with organic polypyrrole which has outstanding flexible photoelectric character. Morphological studies reveal the uniform growth of Ppy nanospheres over the porous Ni foam substrate that provides a large surface to volume ratio for efficient interaction of photons. Optical studies show excellent absorption in the UV region and a soret peak in the visible region while structural studies confirm the formation of polypyrrole with C=C stretching and C=N stretching modes. The Ppy/Ni foam-based photodetector displays excellent response with responsivity of 6.5 A/W, 5.4 A/W and 17.3 A/W in the UV, visible and NIR region of the spectrum, respectively for a minimum bias voltage of 1 mV. The spectral detectivity of the device was obtained as 1011 Jones demonstrating a least noise equivalent power. The acquired performance can be attributed to the synergistic effect of photon excitation as well as molecular-phonon vibration upon illumination of light. A maximum EQE of 27.56 was achieved for NIR light owing to the trap-assisted charge carrier tunneling injection from the Ppy/Ni interface. The solution processed Ppy/Ni foam photodetector proves to be a better alternative for broad band photodetection over previously reported organic photodetectors fabricated using sophisticated techniques. The strategy employed here paves new path for synthesis and fabrication of organic photodetectors towards optoelectronic applications.

Top‐Illuminated Organic Photodetectors beyond 1000 nm Wavelength Response Enabled by a Well‐Defined Interfacial Engineering

AbstractNear infrared (NIR) and shortwave infrared (SWIR) image technologies are of interest for many emerging applications. Among photodetector technologies, organic photodetectors (OPDs) are groundbreaking light sensors with unique photon‐to‐electron responses at various wavelengths that offer limitless flexibility in field applications due to the tunable design of organic semiconductors. Herein, a top‐illuminated OPD deposited on bottom aluminum electrode with a spectral response beyond a wavelength of 1000 nm is reported, which suggests a feasibility for image sensors integrated with bottom readout circuit. The results reveal that a device composed of aluminum‐doped zinc oxide, nickel oxide, and indium‐doped zinc oxide as hole blocking layer, hole transporting layer, and transparent top electrode, respectively, shows the best performance at a wavelength of ≈1000 nm, achieving an outstanding external quantum efficiency of 74% with a responsivity of 0.64 A W−1 and a detectivity of 6.6 × 1012 Jones. The device also performs a fast photocurrent response time of 9.8 µs and a linear dynamic range of 98 dB. To the best of knowledge, this device performance is one of the best reported to date for NIR and SWIR OPDs. The values are also comparable to commercially available inorganic photodetectors.

Electrically Switchable Color-Selective Organic Photodetectors for Full-Color Imaging.

The present full-color imaging techniques rely on the use of broadband inorganic photodetectors with dedicated color filters, which is one of the practical challenges for large-area, flexible, and high-solution imaging applications. The development of high-performance color-selective photodetectors is one of the key solutions to overcome this challenge. In this work, an electrically switchable color-selective organic photodetector (OPD) comprising a double organic bulk heterojunction structure has been developed for full-color imaging. The color-selective sensing capability over the visible spectrum ranges can be realized by controlling the bias across the OPD, achieving a high responsivity of ∼200 mA/W, a large linear dynamic range of 122 dB, a viewing angle of 120°, and a -3 dB cutoff frequency of >50 kHz. A full-color imaging function has been demonstrated using electrically switchable red-, green-, and blue-color selective OPD sensors with an excellent operational stability. The results of this work provide a practical solution for applications in high-resolution full-color imaging and artificial vision.

The Basic Category and Application of Graphene-based Hybrid Photodetector

A photodetector is an optoelectronic device that can be divided into inorganic photodetector, which consists of traditional semiconductors, and organic photodetector, the recent direction of researching that made of organic semiconductors with the help of organic dye molecular or other organic compounds. The core of the improvement of photodetector is graphene, a single layer of the two-dimensional (2D) carbon crystalline structure, which provides the property with wide spectral bandwidth and considerably high response speed. This review focuses on the basic knowledge about graphene-based hybrid photodetector, because the hybrid photodetectors have the advantages of breaking the limitation of light absorption and shortening the recombination time of electrons and holes to increase photoresponsivity. Photodetectors can also behave differently when lights are in the infrared, ultraviolet, and terahertz region, so that the selection of materials based on graphene to detect the specific wavelengths of light becomes a challenge. In order to explain the complicated advanced technology briefly, this review can be regarded as two main parts. The first one is the basic properties of inorganic and organic photodetectors with the addition of perovskite, a new material that has been extensively studied recently, and the second part is about how photodetectors can be applied in a different wavelength of lights.

Self-powered broadband hybrid organic–inorganic photodetectors based on PEDOT:PSS and silicon micro-nanostructures

Structural modifications to the surface of the active layer of hybrid organic-inorganic self-powered broadband photodetectors lead to a remarkable enhancement in their photoresponse.

Flexible Short-Wave Infrared Image Sensors Enabled by High-Performance Polymeric Photodetectors

High-performance short-wave infrared (SWIR) photodetectors (PDs) possess great potential in health monitoring, remote control, telecommunication, and medical diagnostics. In comparison with inorganic PDs, organic PDs (OPDs) stand out as good candidates for next-generation photodetection devices because of their ease of processing, tunable optoelectronic properties, lightweight, easy portability, and low-manufacturing cost. Herein, we reported two conjugated polymers with ultranarrow band gaps (0.6 eV) for photoconductor-mode SWIR OPDs, which exhibited broad and excellent photoresponse across the visible and IR regions as long as 1450 nm. Specifically, one of the polymers possessing longer exciton lifetimes and favorable morphology and molecular orientation was further applied for flexible OPDs, demonstrating excellent performance with the responsivity (R) and external quantum efficiency as high as 0.96 A/W and 106% at 1122 nm, respectively, comparable to those of 2D nanomaterial-based IR PDs. In addition, an image sensor composed of 16 × 16 flexible OPDs was constructed, which can detect spatial light intensity distribution (1342 nm) clearly. This contribution shed light on designing excellent conjugated polymers for high-performance photoconductor-mode OPDs, which can be employed for SWIR light image sensors.

On the Origin of Dark Current in Organic Photodiodes

AbstractMinimizing the reverse bias dark current while retaining external quantum efficiency is crucial if the light detection sensitivity of organic photodiodes (OPDs) is to compete with inorganic photodetectors. However, a quantitative relationship between the magnitude of the dark current density under reverse bias ( Jd) and the properties of the bulk heterojunction (BHJ) active layer has so far not been established. Here, a systematic analysis of Jd in state‐of‐the‐art BHJ OPDs using five polymers with a range of energy levels and charge transport characteristics is presented. The magnitude and activation energy of Jd are explained using a model that assumes charge injection from the metal contacts into an energetically disordered semiconductor. By relating Jd to material parameters, insights into the origin of Jd are obtained that enable the future selection of successful OPD materials.

Doping induced performance enhancement in inverted small molecule organic photodiodes operating below 1V reverse bias - Towards compatibility with CMOS for imaging applications

Abstract Organic photodiodes (OPDs) offer a myriad of advantages over conventional inorganic photodetectors, making them particularly attractive for imaging application. One of the key challenges preventing their utilization is the need for their integration into the standard CMOS processing. Herein, we report a CMOS-compatible top-illuminated inverted small molecule bi-layer OPD with extremely low dark leakage current. The device utilizes a titanium nitride (TiN) bottom electrode modified by a [6,6]-phenyl C61 butyric acid methyl ester (PCBM) cathode buffer layer (CBL). We systemetically show that doping the CBL enhances device's low voltage (below 1 V reverse bias) photoresponse by increasing the linear dynamic range (LDR) and making the bandwidth of the photodidoe broader without compromising the leakage current. The optimized device exhibits a dark leakage current of only ∼6 × 10−10 A/cm2 at −0.5 V. The external quantum efficiency (EQE) at 500 nm reaches 23% with a calculated specific detectivity as high as 7.15 × 1012 cm Hz1/2/W (Jones). Also the LDR approaches 140 dB and the bandwidth is about 400 kHz, at −0.5 V bias. The proposed device structure is fully compatible with CMOS processing and can be integrated onto a CMOS readout circuit offering the potential to be applied in high-performance large-scale imaging arrays.