Hybrid Photodiode Research Articles

Benzyl viologen dichloride as a novel ligand for CdSe CQDs in hybrid QDs/organic photodiodes

The use of colloidal quantum dots (CQDs) in advanced optoelectronic devices requires the substitution of bulky long ligands with short organic ligands. The search for a short-ligand that can create stable quantum solids without compromising the confinement of the CQDs is of paramount importance.Within this context, we present a novel surface passivation ligand, benzyl viologene dichloride (BVD-Cl), as a replacement for the conventional trioctylphosphine oxide (TOPO) capping of CdSe CQDs. BVD-Cl enables the creation of a CdSe quantum solid while retaining quantum confinement. To demonstrate the efficacy of this ligand-exchange process, we utilised Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectrometry (EDX), high-resolution transmission electron microscopy (HR-TEM), and X-ray photoemission spectroscopy (XPS). We then implanted the new BVD-Cl:CdSe quantum film as the main inorganic QDs layer into a hybrid photodiode combined with poly 3-hexylthiophene (P3HT) as the organic layer. The photodiode demonstrated high sensitivity to light stimuli and rectifying behaviour, with a responsivity of 70 mA/W at 550 nm. Our observations imply that using BVD-Cl as a surface passivation ligand for CQDs has significant implications for the development of advanced optoelectronic devices.

Silicon distyryl-BODIPY hybrid photodiode: moving a step ahead from organic interface layer to type II band alignment

Organic-inorganic heterojunctions are becoming an attractive topic of research for their applications in hybrid photodetectors, solar cells, resistive switching memory devices etc. The easy chemical synthesis and low-cost fabrication for organic thin films come with the benefit of high light absorptivity, high fluorescence quantum yield and band gap tunability along with high charge carrier lifetime that could be combined with the existing silicon-based technology. In this aspect, various organic dyes utilised as an interfacial layer with silicon Schottky junction are reported earlier. However, the photo responses are quite limited. Here, in this report, a Type II Silicon/Distyryl-BODIPY p-n junction has been proposed as an organic-inorganic hybrid photodetector which has not been explored extensively yet. The transformation from a mere organic interfacial layer to band aligned junction enhances the charge carrier separation providing higher photo-responsive behaviour. With the simple spin-coating technique, the Distyryl-BODIPY derivative with phenolic functionalities is coated to fabricate the p-n junction diode. To further improve the performance, pyramidal surface texturization on silicon is deployed using wet chemical etching that supplements the light absorption with internal reflections. Both the devices have been investigated for their photo-response characteristic where a high photo-responsivity of 4353 A W−1 is attained for the textured device as compared to 118 A W−1 for the planar silicon device at a − 3 V bias with an ultra-high specific detectivity of 1012 Jones and 1010 Jones respectively. The behaviours of interfacial states have been demonstrated using the capacitance (C), conductance (G) and series resistance (RS) vs voltage (V) curves at different frequencies. Further calculations of interfacial state density revealed the existence of 1000 times higher interfacial states in planar device leading to lower performance as compared to pyramidal device. The findings in this report suggest that dye-based organic-inorganic heterostructures find potential applications in photodetectors and other optoelectronic devices.

Recent advances in two-dimensional graphitic carbon nitride based photodetectors

Graphitic carbon nitride (g-C3N4) is a kind of low cost and environment-friendly 2D polymer semiconductor that exhibits a tunable band gap, high thermal stability, intriguing optoelectronic properties and broad device applications. However, there is hardly any review of g-C3N4′s recent development in photodetection devices. Herein, we summarized the recent advances in the 2D g-C3N4 based photodetector. Firstly, the structure and optoelectronic properties of 2D g-C3N4 were introduced. Secondly, recent progress in 2D g-C3N4 based photodetectors with different device types, such as 2D g-C3N4 based photoconductor, hybrid nanostructure photodetector, photodiode, perovskite photodetector and piezo-phototronic photodetector were summarized. Finally, some major challenges and opportunities towards the practical optoelectronic device applications of 2D g-C3N4, which need be further investigated, had been discussed. As a pioneer, this review systematically presented the development of 2D g-C3N4 based photodetector in the past years and highlighted their great potential in field of broadband, low-cost, fast-response and high-performance photodetectors. We hope that this review could guide the following development and research of g-C3N4 based photodetectors.

Investigation of fundamental electrical and optoelectronic properties of an organic- and carbon-based MnPc/GC photodiode with high photosensitivity

The aim of this work is to provide an alternative to optoelectronic devices that use carbon and organic materials. To achieve this, we coated a modified MnPc organic semiconductor compound onto a graphite-like carbon (GC) thin film using the thermal evaporation technique, and fabricated an organic-based, highly light-sensitive MnPc/GC hybrid heterojunction. The heterojunction had a transmittance of approximately 60% in the visible region, an absorption coefficient of ∼106 m−1, and an energy band gap of 2.6 eV. Subsequently, Ag contacts were grown on the surface of each layer, and the Ag/MnPc/GC/Ag photodiode was subjected to fundamental electrical analysis at various light intensities and a ±3 V applied potential. Analysis in a dark environment revealed that the photodiode had a rectification ratio of 2.59 × 103, a series resistance of 28 Ω, and a shunt resistance of 4.17 × 104 Ω, as calculated from Ohm’s law. The diode ideality factor and barrier height of the photodiode were determined from thermionic emission theory to be 5.60 and 0.71 eV, respectively, and it was observed that these decreased with increasing light intensity. The photodetector parameters of the MnPc/GC hybrid photodiode were determined under positive and negative applied potentials at various light intensities. The highest photocurrent, photoconductive responsivity, photosensitivity, and specific detectivity were determined to be 1.512 × 10−1 A, 11.52 A.W−1, 9.83 × 105, and 2.48 × 1012 Jones, respectively, which were significantly higher than those reported in literature for organic and inorganic-based photodiodes. Based on the findings, it was concluded that the Ag/MnPc/GC/Ag photodiode holds promise as an alternative for sensors, solar cells, photodetectors, and optoelectronic communications applications.

Organic and Hybrid Diode Features of an n-Type 1,8-Naphthalimide Derivative

Organic–inorganic hybrid photodiodes have garnered research interest to achieve high-performance optoelectronic devices with longer lifetime. In the present study, a fluorescent 1,8-naphthalimide (NI) derivative BHSHNI was synthesized through bromination of 3-hydroxy naphthalic anhydride and subsequent imidation reaction with salicyloyl hydrazide. The IR, NMR and mass spectrometry studies confirmed the molecular structure of the NI derivative. Intramolecular charge transfer was confirmed using theoretical and fluorescence emission studies. Thermal investigations suggested good stability of BHSHNI and cyclic voltammetry indicated an electrochemical band gap of 1.10 eV. Surface uniformity and pit-free morphology was observed in SEM and AFM images of thin films formed by BHSHNI. The organic (PEDOT:PSS) and hybrid (organic–inorganic) p–n type diodes were successfully constructed using BHSHNI. The hybrid diode exhibited better features with ideality factors of 9.3 and 15.2 in dark and visible light, respectively, with a dielectric constant of 7.65 at 30 kHz. The calculated responsivity of the hybrid diode was found to be 66.26 mu mathrm{A}/mathrm{W}. The device incorporating BHSHNI as functional material with NiO can be further explored for photodiode applications.Graphical

Phase 1 upgrade of the CMS Hadron Barrel Calorimeter

The Phase 1 upgrade of the CMS Hadron Calorimeter (HCAL) involved the installation of new silicon photomultiplier devices (SiPMs), which replaced older hybrid photodiodes (HPDs). SiPMs measure the scintillator light output with better signal/noise. The upgraded readout electronics also allow for increased longitudinal segmentation and better performance. This report describes the design, testing, installation, and commissioning of the HCAL Barrel Phase 1 upgrade. Performance results for the HCAL Endcap during Run 2 are presented and expectations for the HCAL Barrel during Run 3 are discussed.

Pomegranate derivative dye/silicon hybrid photodiode for sensor applications

Here, we describe the use of pomegranate peel (PG) biomolecules as a light sensor. For this purpose, PG/n-Si hybrid photodiode was fabricated by coating PG biomolecule on the Si with spin coating method. The density functional theory (DFT) approach was utilized to optimize the geometry of the PG molecules. In the I-V measurements performed in the dark and under the visible light, it was observed that the device exhibited photodiode characteristics. Namely, it was seen that the photo-generated current was extremely larger than the dark current for the reverse current and thus the I-V measurements were performed by expanding it under different light intensity. The open-circuit voltage, the short circuit current, and the on/off ratio of the hybrid photodiode were determined as a function of light intensity. Furthermore, Current-voltage (I-V) and Capacitance-voltage (C-V) measurements of the device were analyzed in detail for dark conditions. The ideality factor, the barrier height, the Fermi level, the diffusion potential, and the series resistance of the PG/n-Si hybrid device were determined.

Phase Retrieval-Based Coherent Receivers: Signal Design and Degrees of Freedom

Kramers-Kronig (KK) detection exploits properties of minimum-phase, single-sideband signals to recover the phase of a signal from its intensity. It offers many of the benefits of standard coherent detection, while not requiring a local oscillator, quadrature hybrid, or balanced photodiodes. Adding a carrier to a transmitted signal to render it minimum-phase, however, causes a power penalty for KK detection relative to standard coherent detection. We study the mutual information (MI) achieved by KK detection and the impact of signal and system design parameters, including excess bandwidth, carrier-to-signal power ratio, modulation order, probabilistic shaping, and chromatic dispersion, making comparisons to standard coherent detection and standard direct detection. We study the effective degrees of freedom for KK detection, confirming that it tends towards unity at high signal-to-noise ratio (SNR), supporting the classification of KK detection as coherent detection. At low SNR, however, KK detection is outperformed by standard direct detection in terms of MI per symbol. This study focuses on the fundamental performance of the detection methods under comparison, by numerically approximating ideal continuous-time signals and signal processing operations. The results and conclusions reported here will be constrained, in practice, by limitations of practical implementation, including those addressed in the Discussion section.

Fabrication of MoS2/ZnO Hybrid Nanostructures for Enhancing Photodetection

In this article, the effect of MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and ZnO blend ratio on the performance of MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> :ZnO hybrid photodiodes is investigated. The UV and visible performance parameters for five different devices consisting of semiconducting layers like MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , ZnO, MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> :ZnO (1:1), MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> :ZnO (1:2), and MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> :ZnO (2:1) each are analyzed. The device MoS2:ZnO (1:2) shows the best performance in the UV region with a responsivity of 17.04 A/W, detectivity of 6.84 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> Jones and external quantum efficiency (EQE) of 6604% at 320nm, -1 V bias. On the other hand, the device MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> :ZnO (2:1) gives the best performance in the visible region with a responsivity of 2.27 A/W, detectivity of 0.60 × 1013 Jones, and EQE of 533% at 529nm, -1 V.

Influence of illumination intensity on electrical characteristics of Eosin y dye-based hybrid photodiode: comparative study

We reported the optoelectronic performance of organic/inorganic hybrid junction photodiode based on Eosin y/silicon (Si). For this purpose, we fabricated Eosin y/n-Si and Eosin y/p-Si structures and demonstrated that both devices exhibited strong photodiode characteristics to the increasing light power depending on current–voltage (I–V) measurements. Furthermore, the XRD and SEM analyses of Eosin y film were performed to analyze structural and topographical features of the film. The electrical measurements of Eosin y/n-Si and Eosin y/p-Si photodiodes were carried out in both dark and under various illumination intensities in the range of 100–400 mW/cm2. The main device parameters, such as ideality factor, barrier height, and responsivities of both devices, were determined from the I–V characteristics. The obtained photocurrent values in reverse biases are higher than the dark current at the same reverse bias for both Eosin y/n-Si and Eosin y/p-Si photodiodes. So, this confirmed that light produces photocurrent due to the formation of electron–hole pairs as a result of light absorption in the Eosin y film. Moreover, the C–V measurements were performed on both photodiodes to characterize capacitive performance of the Eosin y films. The fabricated photodiodes based on Eosin y thin films present great promise for future optoelectronic device applications.

Ultrahigh photovoltage responsivity of PEDOT:PSS–silicon hybrid heterojunction photodiodes

Strong inversion at the poly(3,4-ethylenedioxythiophene): polystyrene sulfonate PEDOT:PSS/silicon interface facilitates the separation of excess carriers and obstructs surface recombination, both are of utmost importance for optoelectronic detectors. In this view, low-temperature solution-processed PEDOT:PSS/silicon hybrid heterojunctions possess great potential for light detection applications. We investigate the performance of hybrid PEDOT:PSS/silicon photodetectors following long-period exposure to ambience. In addition, the effect of PEDOT:PSS conductivity on the performance of hybrid heterojunction photodiodes is also explored. In the self-powered photovoltage mode, the hybrid photodiode displays an ultrahigh responsivity of 106 V/W, a noise equivalent power of 10 pW/Hz, and a detectivity up to 1010 Jones. Thermal noise is identified as the main limiting factor in the device performance. The hybrid photodetector demonstrates a desirable stability over long-time storage in air.

Influence of thermal annealing of Ag NWs/AZO composite films on behavior of Ag NWs/AZO-P3HT photodetectors

Solution-processed silver nanowires (Ag NWs)/AZO composite films were deposited on indium-free transparent conductive layers to yield hybrid photo-diodes. In this study, high-quality Ag NWs/AZO films were prepared by simple and controllable annealing process at 340 °C under nitrogen atmosphere instead of low annealing temperature used previously. P-type polymer poly-3-hexylthiophene-2,5 -diyl (P3HT) was then spin-coated on Ag NWs/AZO top to form p–n junction. Devices annealed under nitrogen showed significant improvement in rectification ratios when compared to those annealed under air at low temperature. The proposed method improved p–n junction diode behavior through tuning defect properties of Ag NWs/AZO by annealing. Ag NWs/AZO photodiode devices exhibited high on/off ratio reaching ∼8 × 103 using Ag NWs/AZO-340 when compared to ∼4 × 102 obtained with Ag NWs/AZO-200. The solution processed indium free Ag NWs/AZO composite film demonstrated superior performance as transparent electrodes, promising for reliable hybrid photodiodes in practical sensors. These findings look promising for simple and competitive detection of defect in Ag NWs/AZO for better future applications in optoelectronics.

Phenol red based hybrid photodiode for optical detector applications

In this study, the phenol red (PR) dye film has been deposited on n-type silicon wafer and SEM, XRD measurements of the film have taken. Then, the PR/n-Si photodiode has been fabricated and (dark) electrical and photoresponse characterization has been analysed. The current-Voltage (I-V) measurements have been carried out at varied light power ranging from 100 mW/cm2 to 400 mW/cm2. Rectification ratios (RR) have been determined as a function of illumination intensities and they are determined as 115.47 for 100 mW/cm2 and 30.26 for 400 100 mW/cm2, respectively. The ideality factor and the barrier height of the Co/PR/n-Si photodiode have been determined as 2.80 and 0.52 eV, respectively in dark. Therefore, it has been seen that the PR/n-Si photodiode performances are strongly dependent on the incident optical power. Namely, the current density has increased remarkably with the power of light at the same reverse bias voltage and this behavior is explained by strong capability of converting a light signal into an electrical for the PR/n-Si photodiode device. Responsivity (R) and detectivity (D*) of the PR/n-Si photodiode are also plotted as a function of illumination intensities for reverse biases and it is found that both parameters are dependent on the illumination intensity. Finally, the capacitance–voltage (C-V) characteristics of the device have been carried out at various frequencies. Obtained experimental results indicate that the PR dye can be used in various optoelectronic applications.

Analysis on different detection mechanisms involved in ZnO-based photodetector and photodiodes

The present study reports on the comparison between the ultraviolet (UV) light detection mechanisms in ZnO-based photodetectors and ZnO/PEDOT:PSS hybrid photodiodes. Using spray pyrolysis method, ZnO thin films were deposited upon glass substrates. The deposition temperature was varied from 350 to 425 °C and the physical properties of ZnO thin films were investigated. The structural analysis reveals that all the prepared ZnO thin films have a preferred orientation along the (002) plane with hexagonal wurtzite structure. The morphological analysis reveals that the grains are uniformly distributed. Electrical properties reveal that the ZnO thin film deposited at 425 °C shows a higher carrier concentration of 3.76 × 1016 cm−3 with low electrical resistivity value of 2.59 × 102 Ω cm. For fabrication of UV photodetectors, the optimum ZnO layer with good electrical and optical property was deposited on ITO substrate with substrate temperature maintained at 425 °C. For the fabrication of hybrid UV photodiodes, poly (3,4 ethylene dioxythiophene):poly (styrene sulphonate) (PEDOT:PSS) and zinc oxide (ZnO) was used as the hole and electron transporting layers, respectively. The current–voltage (I–V) and photoresponse switching characteristics under UV light of the fabricated ZnO-based photodetector and photodiodes were studied and the detection mechanisms of such devices were analysed. It was observed that the ZnO-based photodiodes show higher photoresponsivity (R) value of 0.25 A/W with fast photoresponse switching speed.

Effect of illumination intensity on the characteristics of Co/Congo Red/p-Si/Al hybrid photodiode

In this study, Congo Red (CR) organic dye interlayer was covered by sping coating on p-Si semiconductor wafer and Co/CR/p-Si/Al photodiode was fabricated. The surface morphology of CR film was characterized by SEM measurement. Current–voltage (I–V) characteristics of the photodiode were obtained under different illumination intensities. The electrical, sensitivity, and photoresponsivity properties of Co/CR/p-Si/Al photodiode were investigated using the current–voltage and capacitance–voltage measurements. While the calculated barrier height (Φb) and ideality factor (n) were 0.58 eV and 1.52 under the dark, these values were 0.55 eV and 1.62 under the 400 mW cm−2, respectively. The exponent of photocurrent was found to be 1.10. This value indicates that the photodiode exhibited a linear photocurrent variation with power of the light. It was found that the interface-state intensity of the photodiode decreased from 1.64 × 1015 to 8 × 1012 eV−1 cm−2 under the 400 mW cm−2 light intensity. The rectification rate of photodiode (RR) of the photodiode was found under the dark and illumination. All experimental results indicate that the photodiode exhibits a photoconducting characteristic.

Fabrication of hybrid photodiode systems: BODIPY decorated cyclotriphosphazene covalently grafted graphene oxides

Combination of graphene sheets with various organic/inorganic functional groups could enhance the applications of graphene-based hybrid materials.

The effect of coumarin addition on the electrical characteristics of Al/Coumarin:CdO/p-Si/Al photodiode prepared by drop casting technique

In this study, cadmium oxide thin films deposited on p-Si with different weight ratio of coumarin were prepared by drop casting technique. The effect of coumarin addition in different weight ratios was investigated on the electrical and photosensivity properties of Al/Coumarin:CdO/p-Si organic-inorganic hybrid photodiodes. The current-voltage (I–V) and capacity-conductivity-voltage (C-G–V) characteristics of the diodes were determined in the dark and under various illumination intensities. It is concluded that all samples have excellent rectification properties due to good rectifying ratios found from I–V characteristics of the devices. All photodiodes produced with different coumarin weight ratios were found to have higher photo-current under illuminated conditions than dark conditions. In addition, the highest Iphoto/Idark photosensitivity value was found as 448.78 for the device with a 5% coumarin doping rate under 5 V and 100 mW/cm2 light intensity. Transient photo-current measurements showed that all devices are sensitive to light intensity. Furthermore, capacitance/conductivity-voltage measurements were performed at frequencies ranging from 10 kHz to 1 MHz. The fact that the capacity decreases and conductivity increases with the increasing frequency values was explained with the presence of interface states. The ideality factors of Al /Coumarin:CdO/p-Si/Al photodiodes, prepared with various coumarin doping ratios, are between 4.39 and 7.83. Additionally, the interfacial density (Dit) and serial resistance (Rs) values of the devices were determined to be dependent on the frequency and the coumarin concentration. As a result, produced Al/Coumarin:CdO/p-Si/Al organic-inorganic hybrid devices can be used as photocapacitors and/or photodiodes in electro-optic applications.

(Invited) Efficient Photodetection in 2D Materials and 2D/3D Heterostructures

This talk will focus on efficient and broadband photodetectors made from heterostructures of two-dimensional materials and conventional semiconductors [1], [2]. Graphene/silicon photodiodes show particularly high response, when the graphene is partly separated from the silicon by an oxide [3]. This effect is utilized in a specific contact pattern scheme that includes both regions of graphene/silicon Schottky diodes and graphene/silicon oxide/silicon (MOS) structures to enable highly sensitive G/Si photodiodes [4]. With this design, we achieve an external quantum efficiency (EQE) of > 80% for wavelengths between 380 and 930 nm. The maximum EQE of 98% is observed at 850 nm, where the responsivity also peaks to 635 mA/W. This high value is attributed to the highly effective collection of charge carriers in the MOS parts of the diodes and outperforms conventional Si p-n photodiodes. Based on these results, we define the ‘true’ active area in G/Si photodiodes. The transition metal dichalcogenide (TMD) molybdenum disulfide (MoS2) is an n-type semiconducting 2D material with a direct band gap of ~1.8 eV in single layer form, while bulk MoS2 has an additional indirect band gap of ~1.3 eV. MoS2/Si heterostructure diodes made with multilayer, CVD grown MoS2 yield a maximum spectral response of 8.6 mA/W [1]. Furthermore, MoS2-based photodiodes on flexible substrates will be discussed. Finally, recent results on the TMD platinum diselenide (PtSe2) will be presented. Made from thermally converted platinum at low temperatures [5], [6], PtSe2 is semimetallic and is an efficient absorber in the infrared range [7]. [1] C. Yim et al., “Heterojunction Hybrid Devices from Vapor Phase Grown MoS2,” Sci. Rep., vol. 4, Jun. 2014. [2] S. Riazimehr et al., “Spectral sensitivity of graphene/silicon heterojunction photodetectors,” Solid-State Electron., vol. 115, Part B, pp. 207–212, Jan. 2016. [3] S. Riazimehr et al., “High Photocurrent in Gated Graphene–Silicon Hybrid Photodiodes,” ACS Photonics, vol. 4, no. 6, pp. 1506–1514, Jun. 2017. [4] S. Riazimehr et al., “High Responsivity and Quantum Efficiency of Graphene / Silicon Photodiodes Achieved by Interdigitating Schottky and Gated Regions,” ACS Photonics, 2018. [5] C. Yim et al., “High-Performance Hybrid Electronic Devices from Layered PtSe2 Films Grown at Low Temperature,” ACS Nano, vol. 10, no. 10, pp. 9550–9558, Oct. 2016. [6] C. Yim et al., “Electrical devices from top-down structured platinum diselenide films,” Npj 2D Mater. Appl., vol. 2, no. 1, p. 5, Feb. 2018. [7] C. Yim et al., “Wide Spectral Photoresponse of Layered Platinum Diselenide-Based Photodiodes,” Nano Lett., vol. 18, no. 3, pp. 1794–1800, Mar. 2018.

Electrical and fotoconducting characterization of Al/coumarin:ZnO/Al novel organic-inorganic hybrid photodiodes

Coumarin doped ZnO/p-Si photodiodes were prepared by using the drop casting technique. The effect of coumarin contribution on the photoresponse properties of fabricated Al/Coumarin:ZnO/p-Si/Al organic-inorganic hybrid devices was investigated. Electrical characterization of Al/Coumarin:ZnO/p-Si/Al photodiodes was carried out in the dark and under various illumination intensities with current-voltage (I–V) and capacity/conductivity-voltage (C-G-V) characteristics. The photocurrent of the diodes were found to be higher under illuminated conditions than the dark situation. It was determined that the prepared photodiodes exhibit photovoltaic behavior. Also, the photosensitivity properties of photodiodes were investigated. The highest photosensitivity expressed as Iphoto/Idark ratio was found as 894.73 for the specimen having 3% coumarin weight ratio under the conditions of 100 mW/cm2 and 5 V. Transient photocurrent measurements confirmed that the photocurrent is sensitive to light intensity. In addition, capacitance/conductivity-voltage measurements were accomplished in frequencies between 10 kHz and 1 MHz. As a result of the continuous distribution of interface states, the capacity decreased with increasing frequency. It was determined that all photodiodes produced exhibit a linear photoconductivity behavior. The calculated ideality factors for Al/Coumarin:ZnO/p-Si/Al photodiodes prepared with various coumarin weight ratios exhibited that the non-ideal behaviors due to surface states and oxide layer. In addition, it was understood that the values of the barrier height and the interfacial density of the diodes could be changed with the doped of coumarin. As a result, it is concluded that the produced organic-inorganic devices can be used as optical sensors for optoelectronic applications.

New method of out-of-time energy subtraction for the CMS hadronic calorimeter

The CMS hadronic calorimeter employs plastic scintillator active material in the barrel and endcap (HBHE). In Run 2, the LHC operates at 13 TeV center-of-mass energy with up to 50 simultaneous collisions per bunch crossing (pileup) and a 25 ns bunch spacing. The HBHE scintillator light pulse is only 60% contained in a 25 ns window, resulting in significant pulse overlap for consecutive events (out-of-time pileup). This talk presents a novel algorithm that will be used in 2018 for subtracting out-of-time pileup in HBHE both online in the software trigger and offline. The algorithm includes methods for both the barrel with hybrid photodiode photosensors and QIE8 digitizers, and the endcap with silicon photomultipliers and QIE11 digitizers, including the challenging charge-dependent pulse shaping effects of the QIEs. The on-detector pulse shape measurement method and results are also shown. The new algorithm is five-to-ten times faster than the previous one, and for the first time CMS will use the offline method at the trigger level.