Metal halide perovskite photodiodes (PPDs) offer high responsivity and broad spectral sensitivity, making them attractive for low-cost visible and near-infrared sensing. A significant challenge in ...achieving high detectivity in PPDs is lowering the dark current density (J
) and noise current (i
). This is commonly accomplished using charge-blocking layers to reduce charge injection. By analyzing the temperature dependence of J
for lead-tin based PPDs with different bandgaps and electron-blocking layers (EBL), we demonstrate that while EBLs eliminate electron injection, they facilitate undesired thermal charge generation at the EBL-perovskite interface. The interfacial energy offset between the EBL and the perovskite determines the magnitude and activation energy of J
. By increasing this offset we realized a PPD with ultralow J
and i
of 5 × 10
mA cm
and 2 × 10
A Hz
, respectively, and wavelength sensitivity up to 1050 nm, establishing a new design principle to maximize detectivity in perovskite photodiodes.
Organic photodetectors (OPDs) have gained increasing interest as they offer cost‐effective fabrication methods using low temperature processes, making them particularly attractive for large area ...image detectors on lightweight flexible plastic substrates. Moreover, their photophysical and optoelectronic properties can be tuned both at a material and device level. Visible‐light OPDs are proposed for use in indirect‐conversion X‐ray detectors, fingerprint scanners, and intelligent surfaces for gesture recognition. Near‐infrared OPDs find applications in biomedical imaging and optical communications. For most applications, minimizing the OPD dark current density (Jd) is crucial to improve important figures of merits such as the signal‐to‐noise ratio, the linear dynamic range, and the specific detectivity (D*). Here, a quantitative analysis of the intrinsic dark current processes shows that charge injection from the electrodes is the dominant contribution to Jd in OPDs. Jd reduction is typically addressed by fine‐tuning the active layer energetics and stratification or by using charge blocking layers. Yet, most experimental Jd values are higher than the calculated intrinsic limit. Possible reasons for this deviation are discussed, including extrinsic defects in the photoactive layer and the presence of trap states. This provides the reader with guidelines to improve the OPD performances in view of imaging applications.
Organic photodetectors (OPDs) are promising for large area image detectors. Minimizing the dark current density (Jd) is crucial in most applications; nevertheless, a wide range of Jd values has been reported. Here, possible reasons that lead to this large variation are discussed. A quantitative analysis of intrinsic Jd processes shows that charge injection from the electrodes is the dominant mechanism.
Organic bulk heterojunction photodiodes (OPDs) attract attention for sensing and imaging. Their detectivity is typically limited by a substantial reverse bias dark current density (Jd). Recently, ...using thermal admittance or spectral photocurrent measurements, Jd has been attributed to thermal charge generation mediated by mid‐gap states. Here, the temperature dependence of Jd in state‐of‐the‐art OPDs is reported with Jd down to 10−9 mA cm−2 at −0.5 V bias. For a variety of donor‐acceptor bulk‐heterojunction blends it is found that the thermal activation energy of Jd is lower than the effective bandgap of the blends, by ca. 0.3 to 0.5 eV, but higher than expected for mid‐gap states. Ultra‐sensitive sub‐bandgap photocurrent spectroscopy reveals that the minimum photon energy for optical charge generation in OPDs correlates with the dark current thermal activation energy. The dark current in OPDs is attributed to thermal charge generation at the donor‐acceptor interface mediated by intra‐gap states near the band edges.
The dark current in optimized organic donor‐acceptor photodiodes is thermally activated with an energy lower than the effective bandgap and that corresponds to the minimum energy for optical charge generation as determined by photocurrent spectroscopy. This demonstrates that dark current is caused by thermal charge generation at the donor‐acceptor interface and mediated by intra‐gap states near the band edges.
Photovoltaic retinal prostheses show great potential to restore sight in patients suffering from degenerative eye diseases by electrical stimulation of the surviving neurons in the retinal network. ...Herein, organic photodiodes (OPDs) sensitive to near‐infrared (NIR) light are evaluated as photovoltaic pixels for future application in retinal prostheses. Single‐junction and tandem OPDs are compared. In the latter, two nominally identical single‐junction cells are processed on top of each other, effectively doubling the open‐circuit voltage (V
OC). Both single‐junction and tandem OPD micropixels can deliver the required charge to stimulate neurons under pulsed NIR light at physiologically safe intensities when connected to stimulating microelectrodes in a physiological saline solution. However, only tandem OPD pixels can cover the entire charge per pulse neural stimulation window due to their higher V
OC (≈1.4 V). This demonstrates the viability of high‐resolution retinal prostheses based on flexible OPD arrays.
Organic photodiodes (OPDs) sensitive to near‐infrared light are evaluated for their application in artificial retinal implants. The electrical charge photogenerated by tandem OPD micropixels reaches the typical neural stimulation levels upon 4 ms light pulses at physiologically safe intensities. This paves the way toward the future development of high‐resolution retinal prostheses based on flexible OPD arrays.
Acute myeloid leukemia remains difficult to treat due to strong genetic heterogeneity between and within individual patients. Here, we show that Pyruvate dehydrogenase kinase 1 (PDK1) acts as a ...targetable determinant of different metabolic states in acute myeloid leukemia (AML). PDK1
AMLs are OXPHOS-driven, are enriched for leukemic granulocyte-monocyte progenitor (L-GMP) signatures, and are associated with FLT3-ITD and NPM1cyt mutations. PDK1
AMLs however are OXPHOS
, wild type for FLT3 and NPM1, and are enriched for stemness signatures. Metabolic states can even differ between genetically distinct subclones within individual patients. Loss of PDK1 activity releases glycolytic cells into an OXPHOS state associated with increased ROS levels resulting in enhanced apoptosis in leukemic but not in healthy stem/progenitor cells. This coincides with an enhanced dependency on glutamine uptake and reduced proliferation in vitro and in vivo in humanized xenograft mouse models. We show that human leukemias display distinct metabolic states and adaptation mechanisms that can serve as targets for treatment.
Minimizing 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.
The reverse bias dark current density in organic bulk heterojunction photodiodes and its activation energy are measured and successfully reproduced in terms of thermal charge injection from the contacts into a broadened density of states at the interface. The agreement is excellent for five polymer semiconductors with widely varying energy levels and charge transport characteristics.
Low‐dimensional perovskites attract increasing interest due to tunable optoelectronic properties and high stability. Here, it is shown that perovskite thin films with a vertical gradient in ...dimensionality result in graded electronic bandgap structures that are ideal for photodiode applications. Positioning low‐dimensional, vertically‐oriented perovskite phases at the interface with the electron blocking layer increases the activation energy for thermal charge generation and thereby effectively lowers the dark current density to a record‐low value of 5 × 10−9 mA cm−2 without compromising responsivity, resulting in a noise‐current‐based specific detectivity exceeding 7 × 1012 Jones at 600 nm. These multidimensional perovskite photodiodes show promising air stability and a dynamic range over ten orders of magnitude, and thus represent a new generation of high‐performance low‐cost photodiodes.
Perovskite thin films with a 2D–3D gradient result in graded electronic bandgap structures that are ideal for photodiode applications. Low‐dimensional perovskite phases at the interface with the electron blocking layer increase the activation energy for thermal charge generation and thereby effectively lower the dark current density to a record‐value of 10–9 mA cm–2, resulting in maximized sensitivity.
•Depth of invasion (DOI) is associated with lymph node metastasis in oral cancer (OC).•The AJCC (8th edition) definition of DOI in OC is recommended.•DOI ≥ 4 mm is an accurate cut-off value for ...elective neck dissection (END).•END performed for patients with DOI ≥ 4 mm results in lower regional recurrence.
Depth of invasion (DOI) is the most important predictor for lymph node metastasis (LNM) in early stage (T1-T2) oral cancer. The aim of this study is to validate the cut-off value of 4 mm on which the decision to perform an Elective Neck Dissection (END) is made.
We performed a retrospective study in patients with pathologically proven early stage oral cavity squamous cell carcinoma (OCSCC) without clinical or radiological signs of LNM, who were treated between 2013 and 2018. An END was performed when DOI was ≥ 4 mm and a watchful waiting protocol was applied in patients with DOI < 4 mm.
Three hundred patients were included. END was performed in 77% of patients with DOI ≥ 4 mm, of which 36% had occult LNM (pN+). Patients in the watchful waiting group (48%) developed a regional recurrence in 5.2% for DOI < 4 mm and 24.1% for DOI ≥ 4 mm. For DOI ≥ 4 mm, regional recurrence free survival was higher for patients who were treated with END compared to watchful waiting (p = 0.002). A Receiver-Operator-Curve -analysis showed that a DOI cut-off value of 4.0 mm was the optimal threshold for the prediction of occult LNM (95.1% sensitivity, 52.9% specificity).
A DOI of ≥ 4 mm is an accurate cut-off value for performing an END in early stage OCSCC. END results in higher survival rates and lower regional recurrence rates in patients with DOI ≥ 4 mm.
An enriched environment for residents with dementia may have a positive effect on the rest-activity rhythm. A small scaled homelike special care unit might be such an enriched environment. The ...present study shows whether the rest-activity rhythm of residents with moderate to severe dementia responds positively to a transfer from a regular Special Care Unit (SCU) to a small scaled homelike SCU.
Initially, a group of 145 residents living in a regular SCU participated. Out of this group, 77 residents moved to a small scaled homelike SCU. This group was compared to the group of 68 residents that remained at the regular SCU. Rest-activity rhythm was assessed by means of actigraphy and observation scales before and after relocation.
No significant main effects nor significant interaction effects in intradaily and interdaily activity were found for the data of 38 residents in the small scaled homelike SCU and 20 residents of the regular SCU. The effect sizes, however, ranged from small to large.
Considering the effect sizes, a new study with a larger number of participants is necessary before firm conclusions can be drawn.
Current Controlled Trials ISRCTN11151241 . registration date: 21-06-2017. Retrospectively registered.
Trap states in organic semiconductors are notoriously detrimental to the performance of organic electronics. However, the origin and energetics of trap states remain largely elusive and under debate, ...especially for bulk‐heterojunction (BHJ) photodiodes consisting of electron donor and acceptor materials. Combining three sensitive techniques now enables locating the origin and energy of trap states in six state‐of‐the‐art polymer – non‐fullerene acceptor organic photodiodes (OPDs) with noise‐based specific detectivities exceeding 1013 Jones. Analyzing the temperature dependence of the reverse‐bias dark current density (Jd) identifies intra‐gap states in the polymers, lying 0.3−0.4 eV above the energy of the highest occupied molecular orbital, as being responsible for Jd. Sub‐bandgap external quantum efficiency spectra of donor‐only and acceptor‐only diodes confirm that intra‐gap states are much more abundant in the polymers. Likewise, responsivity measurements at ultra‐low light intensities (10−7 mW cm−2) show trap‐mediated charge recombination in BHJ and polymer‐only diodes, but not in acceptor‐only devices. The results imply that to further improve the specific detectivity of near‐infrared OPDs, the intra‐gap state energy, and density need to be reduced.
Temperature‐dependent dark current measurements, combined with sensitive photocurrent spectra and responsivity measurements at ultra‐low light intensities, show that intra‐bandgap states located ≈0.3−0.4 eV above the highest occupied molecular orbital energy of the donor are the origin of the thermally activated reverse dark current in state‐of‐the‐art organic photodiodes comprising conjugated polymer donors and non‐fullerene acceptors.
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