Reducing the dark current density (Jd) of organic photodetectors (OPD) is an effective way to improve some important figures of merits such as on-off ratio and specific detectivity (D*). Many studies have demonstrated that increasing the thickness of the active layer can effectively reduce the Jd of OPD, but at the same time it can cause a sharp decrease in responsivity and external quantum efficiency (EQE). In this work, a preheating spin coating method was used on the thick bulk-heterojunction (BHJ) active layer, which is composed of a polymer donor PBDB-T and a non-fullerene acceptor (NFA) Y6 with near-infrared (NIR) absorption. As a result, the thick BHJ OPD maintains a low Jd while the responsivity and EQE are greatly improved, therefore the optimized devices display a high D* over 1012 Jones at -0.5 V from 400 nm to 900 nm, indicating its application potential in visible-to-NIR detection. This work provides an effective strategy to enhance the performance of thick BHJ devices.
In this work, a modeling for reactive sputtering has been presented where the non-uniform current density is taken into account. The model in this paper can be used to understand the process of reactive magnetron sputtering. The results are compared with those that assume uniform discharge current density distributed on the target. It can be concluded that the process with the non-uniform discharge density shows a higher flow of gas reactive when occurring the hysteresis behavior. In addition, a study of the radial variation of the target composition in metallic and compound mode is also performed.
Hydrogen-bond acidic (HBA) polymers are widely used for the detection of dimethyl methyl phosphonate (DMMP, a simulant of real nerve agents) based on surface acoustic wave (SAW) sensors. This paper presented an HBA polymer PLF, and subsequently the polymer was dissolved into chloroform and spray-coated on a SAW device to fabricate a gas sensor. Then the sensor was equipped into a SAW test platform to investigate its sensitive property to soman vapor and its simulant DMMP at the concentrations below 20 mg/m3. Results revealed that the sensor showed high sensitivity to the analyte vapors, furthermore, the response of the sensor to soman vapor was relatively smaller and slower than that to DMMP. Tests to some common interference vapors were studied at the concentration of 10 mg/m3, and the results indicated that the sensor showed a good selective property.
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