Organic Photodetectors Research Articles

Vertically Phase Separated Photomultiplication Organic Photodetectors with p-n Heterojunction Type Ultrafast Dynamic Characteristics.

Photomultiplication (PM)-type organic photodetectors (OPDs), which typically form a homogeneous distribution (HD) of n-type dopants in a p-type polymer host (HD PM-type OPDs), have achieved a breakthrough in device responsivity by surpassing a theoretical limit of external quantum efficiency (EQE). However, they face limitations in higher dark current and slower dynamic characteristics compared to p-n heterojunction (p-n HJ) OPDs due to inherent long lifetime of trapped electrons. To overcome this, a new PM-type OPD is developed that demonstrates ultrafast dynamic properties through a vertical phase separation (VPS) strategy between the p-type polymer and n-type acceptor, referred to as VPS PM-type OPDs. Notably, VPS PM-type OPDs show three orders of magnitudeincrease in -3dB cut-off frequency (120kHz) and over a 200-fold faster response time (rising time = 4.8 µs, falling time = 8.3 µs) compared to HD PM-type OPDs, while maintaining high EQE of 1121% and specific detectivity of 2.53 × 1013 Jones at -10V. The VPS PM-type OPD represents a groundbreaking advancement by demonstrating the coexistence of p-n HJ and PM modes within a single photoactive layer for the first time. This innovative approach holds the potential to enhance both static and dynamic properties of OPDs.

Highly-efficient low-cost polarization-sensitive organic photodetectors based on laminated self-assembly planar and bulk heterojunctions

To overcome the severe problems arising from the insufficient light absorption of ultrathin self-assembly active layers and the high cost use of atomic force deposition (ALD)-grown low-leakage-current transport layers, we successfully developed a low-cost, simple and facile strategy of floating-film transfer and multilayer lamination (FFTML) for constructing highly-efficient ALD-free broadband polarization-sensitive organic photodetectors (OPDs) with the two commonly used structures of donor/acceptor planar heterojunction (PHJ) and donor:acceptor multilayer bulk heterojunction (BHJ). It was found that the PHJ-based polarization-sensitive OPD by FFTML possesses a low dark current due to the high carrier injection barrier, indicating it is more suitable to be applied in low polarized light detection scenarios. In contrast, the BHJ-based device by FFTML has a higher spectral responsivity in the whole wavelength due to more photo-excitons transferred to the donor:acceptor interface and dissociated into photoexcited carrirers. Furthermore, the film thickness, which is tuned by increasing lamination number of BHJ layers, has a big effect on the polarization-sensitive photodetection performance. The polarization-sensitive 4-BHJ OPD by FFTML finally achieved a high specific detectivity of 8.33 × 1010 Jones, which was much higher than 2.72 × 1010 Jones for the 2-BHJ device at 0 V. This work demonstrates that layer-by-layer lamination of self-assembly films can effectively improve the polarized-light detection performance, contributing significantly to the rapid development of the field.

Nonfiltered organic photodetector with high narrowband response in near-infrared for optical communication

Nonfiltered organic photodetector with high narrowband response in near-infrared for optical communication

Optimizing P3HT/PCBM-Based Organic Photodetector Performance: Insights from SCAPS 1D Simulation Studies.

Organic electronics have great potential due to their flexible structure, high performance, and their ability to build effective and low-cost photodetectors. We investigated the parameters of the P3HT and PCBM layers for device performance and optimization. SCAPS-1D simulations were employed to optimize the thicknesses of the P3HT and PCBM layers, investigate the effects of shallow doping in the P3HT layer, and assess the influence of the back contact electrode's work function on device performance. Furthermore, this study explored the impact of interface defect layer density on the characteristics of the device. Through systematic analyses, the optimal parameters for enhancing device responsivity were identified. The findings indicate that a P3HT layer thickness of 1200 nm, a PCBM layer thickness of 20 nm, and a back contact electrode with a work function of 4.9 eV achieve the highest responsivity. Notably, at a bias of -0.5 V, the responsivity exceeds 0.4 A/W within the wavelength range of 450 nm to 630 nm. These optimized parameters underscore the significant potential of the developed device as an organic photodetector, particularly for visible light detection.

A microsized optical spectrometer based on an organic photodetector with an electrically tunable spectral response

A microsized optical spectrometer based on an organic photodetector with an electrically tunable spectral response

Improved Performance of Inverted Near-Infrared Organic Photodetectors Based on ZnO/PFN as Double-Layer Interfacial Materials

Improved Performance of Inverted Near-Infrared Organic Photodetectors Based on ZnO/PFN as Double-Layer Interfacial Materials

Fabrication of hybrid organic and inorganic photodetector

Fabrication of hybrid organic and inorganic photodetector

A fully-fluorinated all-fused-ring acceptor for highly sensitive near-infrared organic photodetectors

A fully-fluorinated all-fused-ring acceptor for highly sensitive near-infrared organic photodetectors

Dual-Band Photomultiplication-Type Organic Photodetectors with Ultrahigh Signal-to-Noise Ratios.

A series of dual-band photomultiplication (PM)-type organic photodetectors (OPDs) were fabricated by employing a donor(s)/acceptor (100:1, wt/wt) mixed layer and an ultrathin Y6 layer as the active layers, as well as by using PNDIT-F3N as an interfacial layer near the indium tin oxide (ITO) electrode. The dual-band PM-type OPDs exhibit the response range of 330-650 nm under forward bias and the response range of 650-850 nm under reverse bias. The tunable spectral response range of dual-band PM-type OPDs under forward or reverse bias can be explained well from the trapped electron distribution near the electrodes. The dark current density (JD) of the dual-band PM-type OPDs can be efficiently suppressed by employing PNDIT-F3N as the anode interfacial layer and the special active layers with hole-only transport characteristics. The light current density (JL) of the dual-band PM-type OPDs can be slightly increased by incorporating wide-bandgap polymer P-TPDs with relatively large hole mobility (μh) in the active layers. The signal-to-noise ratios of the optimized dual-band PM-type OPDs reach 100,980 under -50 V bias and white light illumination with an intensity of 1.0 mW·cm-2, benefiting from the ultralow JD by employing wide-bandgap PNDIT-F3N as the anode interfacial buffer layer and the increased JL by incorporating appropriate P-TPD in the active layers.

High‐Detectivity UV–Visible–NIR Broadband Polymer Photodetector with Polymer Charge Blocking Layer Cross‐Linked by Organic Photocrosslinker

AbstractUltraviolet (UV), visible, and near‐infrared (NIR) broadband organic photodetectors are fabricated by sequential solution‐based thin film coatings of a polymer electron blocking layer (EBL) and a polymer photoactive layer. To avoid damage to a preceding polymer EBL during a subsequent solution‐based film coating of a polymer photoactive layer due to lack of solvent orthogonality, 2‐(((4‐azido‐2,3,5,6‐tetrafluorobenzoyl)oxy)methyl)−2‐ethylpropane‐1,3‐diyl bis(4‐azido‐2,3,5,6‐tetrafluorobenzoate) (FPA‐3F) is used as a novel organic cross‐linking agent activated by UV irradiation with a wavelength of 254 nm. Solution‐processed poly[N,N′‐bis(4‐butylphenyl)‐N,N′‐bis(phenyl)‐benzidine] (poly‐TPD) films, which are cross‐linked with a FPA‐3F photocrosslinker, are used for a preceding polymer EBL. A ternary blend film composed of PTB7‐Th, COi8DFIC, and PC71BM is used as a NIR‐sensitive organic photoactive layer with strong photosensitivity in multispectral (UV–visible–NIR) wavelengths of 300–1,050 nm. Poly‐TPD films are successfully cross‐linked even with a very small amount of 1 wt% FPA‐3F. Small amounts of FPA‐3F have little detrimental effect on the electrical and optoelectronic properties of the cross‐linked poly‐TPD EBL. Finally, organic NIR photodetectors with a poly‐TPD EBL cross‐linked by the small addition of FPA‐3F (1 wt%) show the detectivity values higher than 1 × 1012 Jones for the entire UV–visible–NIR wavelengths from 300 nm to 1050 nm, and the maximum detectivity values of 1.41 × 1013 Jones and 8.90 × 1012 Jones at the NIR wavelengths of 900 and 1000 nm, respectively.

Ultraflexible Ring‐Shaped Organic Photodetectors for Motion Artifact‐Less Photoplethysmography

AbstractOwing to compact size and affordability, wearable photoplethysmogram sensors provide real‐time physiological parameters that are critical for vital signs monitoring. However, the measurement accuracy, especially during physical activities, is the main obstacle toward clinical practice. Here, ring‐shaped ultraflexible organic photodetectors （OPDs） are proposed that can form conformal contact with the skin fingerprints and monitor pulse wave under faint light source of ≈22 µW cm−2. The ring‐shape and ultraflexible design, together with optimized donor‐acceptor composition, active layer thickness, and large active area (0.1 cm2) endow the OPDs with low dark current (3.66 × 10−10 A cm−2 at −1 V), high detectivity (1.5 × 1013 Jones), and motion artifact‐free when moving at a speed of 5 cm s−1.

Bias‐Switchable Dual‐Mode Organic Photodetector with High Operational Stability Using Self‐Trapped Cs3Cu2I5 Interfacial Layer

AbstractConventional photovoltaic (PV)‐photodetectors are hard to detect fainted signals, while photomultiplication (PM)‐capable devices indispensable for detecting weak light and are prone to degrade under strong light illumination and large bias, and it is urgent to realize highly efficient integrated detecting system with both PM and PV operation modes. In this work, one lead‐free Cs3Cu2I5 nanocrystals with self‐trapping exciton nature was introduced as interfacial layer adjacent to bulk and layer‐by‐layer heterojunction structure, and corresponding organic photodetectors with bias‐switchable dual modes are demonstrated. The fabricated device exhibits low operating bias (0 V for PV mode and 0.8 V for PM mode), high specific detectivity (~1013 Jones), fast response speed as low as 1.59 μs, large bandwidth over 0.2 MHz and long‐term operational stability last for 4 months in ambient condition. This synergy strategy also validated in different materials and device architectures, providing a convenient and scalable production process to develop highly efficient bias‐switchable multi‐functional organic optoelectrical applications.

Bias-Switchable Dual-Mode Organic Photodetector with High Operational Stability Using Self-Trapped Cs3Cu2I5 Interfacial Layer.

Conventional photovoltaic (PV)-photodetectors are hard to detect fainted signals, while photomultiplication (PM)-capable devices indispensable for detecting weak light and are prone to degrade under strong light illumination and large bias, and it is urgent to realize highly efficient integrated detecting system with both PM and PV operation modes. In this work, one lead-free Cs3Cu2I5 nanocrystals with self-trapping exciton nature was introduced as interfacial layer adjacent to bulk and layer-by-layer heterojunction structure, and corresponding organic photodetectors with bias-switchable dual modes are demonstrated. The fabricated device exhibits low operating bias (0 V for PV mode and 0.8 V for PM mode), high specific detectivity (~1013 Jones), fast response speed as low as 1.59 μs, large bandwidth over 0.2 MHz and long-term operational stability last for 4 months in ambient condition. This synergy strategy also validated in different materials and device architectures, providing a convenient and scalable production process to develop highly efficient bias-switchable multi-functional organic optoelectrical applications.

Optimizing the π-Bridge of Non-fullerene Acceptors to Suppress Dark Current in NIR Organic Photodetectors

Optimizing the π-Bridge of Non-fullerene Acceptors to Suppress Dark Current in NIR Organic Photodetectors

Octupole moment driven free charge generation in partially chlorinated subphthalocyanine for planar heterojunction organic photodetectors

In this study, high-performance organic photodetectors are presented which utilize a pristine chlorinated subphthalocyanine photoactive layer. Optical and optoelectronic analyses indicate that the device photocurrent is primarily generated through direct charge generation within the chlorinated subphthalocyanine layer, rather than exciton separation at layer interfaces. Molecular modelling suggests that this direct charge generation is facilitated by chlorinated subphthalocyanine high octupole moment (−80 DÅ2), which generates a 200 meV shift in molecular energetics. Increasing the thickness of chlorinated subphthalocyanine leads to faster response time, correlated with a decrease in trap density. Notably, photodetectors with a 50 nm thick chlorinated subphthalocyanine photoactive layer exhibit detectivities approaching 1013 Jones, with a dark current below 10−7 A cm−2 up to −5 V. Based on these findings, we conclude that high octupole moment molecular semiconductors are promising materials for high-performance organic photodetectors employing single-component photoactive layer.

Ultralow dark current in near-infrared organic photodetector via crosslinked conjugated polyelectrolyte hole-transporting layer

Ultralow dark current in near-infrared organic photodetector via crosslinked conjugated polyelectrolyte hole-transporting layer

Ultralow Dark Current Density of Organic Photodetectors and Organic Light-Emitting Diodes Endowed by Highly Thermally Stable Derivatives of 2,7-Di-tert-butyl-9,9-dimethyl-9,10-dihydroacridine and Phenanthroimidazole Exhibiting Balanced Bipolar Charge Transport

Ultralow Dark Current Density of Organic Photodetectors and Organic Light-Emitting Diodes Endowed by Highly Thermally Stable Derivatives of 2,7-Di-<i>tert</i>-butyl-9,9-dimethyl-9,10-dihydroacridine and Phenanthroimidazole Exhibiting Balanced Bipolar Charge Transport

Ligand‐Triggered MXene Quantum Dots with Tunable Work Function as Anode and Cathode Interlayers for Organic Solar Cells

The interfacial layers of organic optoelectronic devices generally suffer from the problems of difficulty in regulating the work function (WF) and low mobility, which are prone to mismatch of interfacial energy levels and loss of carrier transport energy. Herein, O‐terminated and NH2‐terminated Ti3C2Tx MXenes quantum dots (MQDs) are synthesized to develop efficient O‐MQD hole transfer layer (HTL) and E‐MQD electron transfer layer (ETL) for organic optoelectronic devices of organic solar cells (OSCs) and organic photodetectors (OPDs). It is found that the strong electronic coupling interaction between the surface terminations and matrices enables O‐MQD and E‐MQD with tunable WF and satisfactory conductivity. Consequently, in a binary D18:L8‐BO system, the power conversion efficiencies of the OSC device based on O‐MQD HTL and E‐MQD ETL are 18.62% and 18.15%, respectively. Moreover, the OPDs with O‐MQD HTL and E‐MQD ETL exhibit higher shot‐noise‐limited detectivity (Dshot*) of 1.24 × 1013 and 1.10 × 1013 Jones, respectively, compared to the devices using classic interlayers. These findings provide some insights into the design of advanced dual‐function interlayers for organic optoelectronic devices.

Highly sensitive water pollution monitoring using colloid-processed organic photodetectors

Highly sensitive water pollution monitoring using colloid-processed organic photodetectors

An n-type organoboron polymer for red-light-selective organic photodetectors

An n-type organoboron polymer for red-light-selective organic photodetectors