Wide Bandgap Polymer with Narrow Photon Harvesting in Visible Light Range Enables Efficient Semitransparent Organic Photovoltaics

Piezo-phototronic effect promoted carrier separation in coaxial p-n junctions for self-powered photodetector

The power conversion efficiency (PCE) of organic photovoltaics (OPVs) has exceeded 18% with narrow bandgap, non-fullerene materials Y6 or its derivatives when used as an electron acceptor. The PCE improvement of OPVs is due to strong photon harvesting in near-infrared light range and low energy loss. Meanwhile, ternary strategy is commonly recognized as a convenient and efficient means to improve the PCE of OPVs. In this review article, typical donor and acceptor materials in prepared efficient OPVs are summarized. From the device engineering perspective, the typical research work on ternary strategy and tandem structure is introduced for understanding the device design and materials selection for preparing efficient OPVs.

https://www.mdpi.com/1996-1073/14/14/4200/pdf

Recent Progress of Organic Photovoltaics with Efficiency over 17

UV-Vis-NIR broad-band organic photomultiplication-type photodetectors (OPMPDs) were fabricated with a device structure of indium tin oxide (ITO)/zinc oxide (ZnO)/(∼150 nm) active layers/Au. The active layers consisted of a 2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3-undecyl-9-(undecyloxy)-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2′′,3′′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[3,2-b]indole-2,10-diyl)bis(methaneylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H,1-diylidene))dimalononitrile (Y6-1O):5-(5-(4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)-6-methylbenzo[1,2-b:4,5-b′]dithiophen-2-yl)-4-(2-butyloctyl)-2-yl)-8-(4-(2-butyloctyl)-5-thiophen-2-yl)dithieno[3′,2′:3,4;2′′,3′′:5,6]benzo[1,2-c][1,2,5]thiadiazole (D18-Cl) (1.6 : 1, wt/wt) layer determining the spectral response range and one photomultiplication (PM) layer [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM):poly(3-hexylthiophene-2,5-diyl) (P3HT) (100 : 5, wt/wt). The spectral response of the double-layered OPMPDs was determined by the trapped-hole distribution in PC71BM:P3HT near by Au electrode, which mainly originated from the photogenerated hole in the Y6-1O:D18-Cl layer. The trapped-hole in P3HT induced interfacial band-bending for efficient electron-tunneling injection from the Au electrode. The trapped-hole-induced electron-tunneling injection could be markedly enhanced by increasing the applied voltage, leading to markedly improved external quantum efficiency (EQE) values. The double-layered OPMPDs exhibited a broad spectral response range from 300 to 1000 nm, and achieved a highly effective EQE of approximately 50 400% at 360 nm under an applied voltage of 5 V, which was the highest value among organic photodetectors (OPDs) under the same applied voltage. Moreover, the maximum specific detectivity (D*) of 3 × 1012 jones and a linear dynamic range (LDR) of 120 dB at 810 nm under an applied voltage of 5 V were achieved in the double-layered OPMPDs. This study brings forward a smart strategy to achieve high performance broad-band OPMPDs by employing double-layered thin active layers.

Highly sensitive, broad-band organic photomultiplication-type photodetectors covering UV-Vis-NIR

Bottom surface of active layers and interface of indium tin oxide (ITO) electrodes and active layers play a crucial role in determining the performance of polymer photodetectors with photomultiplication (PM-PPDs). The interfacial trapped electron distribution closing to ITO electrodes will determine spectral response range and external quantum efficiency (EQE) of PMPPDs. The bottom interface is more sensitive than top interface when light is coming from the ITO side, and the larger density of generated charge on the bottom interfaces will induce interfacial band more bending for efficient charge tunneling injection. Highly sensitive and sub-microsecond PM-PPDs are achieved with PMBBDT:Y6 (100:7, w/w) as active layers under forward bias, yielding EQE of 18,700% at 320 nm, 21,700% at 600 nm and 16,400% at 810 nm under a bias of 7 V, respectively, as well as fast response time of 79 μs. The high EQE of the PM-PPDs is attributed to efficient hole tunneling injection from ITO electrode under forward bias. The electron traps closing to ITO electrode will be quickly filled up when light is coming from ITO side, leading to interfacial band more bending for hole tunneling injection. Importantly, the PM-PPDs is performed to measure heart rate (HR) and blood oxygen saturation (SpO2), and the measured data by the PM-PPDs are very similar with those obtained by commercial photodetectors.

Highly sensitive, sub-microsecond polymer photodetectors for blood oxygen saturation testing

The propulsion system is one of the important and vulnerable sub-systems in a strap-on launch vehicle. Among different failure modes, the thrust drop fault is the most common and remediable one. It degrades vehicle attitude tracking ability directly. To this end, this paper focuses on the design and application of attitude reconstruction problems with a thrust loss fault during the ascending flight phase. We firstly analyze the special failure modes and impacts on the propulsion system through a Failure Modes and Effects Analysis (FMEA). Then, six degrees of freedom dynamic and kinematic models are formulated, which are integrated into the Matlab/Simulink environment afterward. The above models’ validation is realized through numerical simulations with different fault severity. Simulation results show that the max attitude deviation is only 0.67° approximately in the pitch angle channel under normal conditions, and the flight attitude angle deviation is directly proportional to the thrust loss percentage when the thrust drop fault occurs. Based on the validated models, a practical reconfigurable ideal through adjusting the control allocation matrix is analyzed. Then, an automation redistribution mechanism based on the moment equivalent principle before and after the thrust drop is proposed to realize proportional allocation of virtual control command among the actuators. The effectiveness of the designed attitude reconstruction method is demonstrated through numerical simulations and comparison analysis under various fault scenarios. The results show that the rocket attitude can be quickly adjusted to the predetermined program angle within about 2.5 s after the shutdown failure of a single engine, and the flight speed and altitude can also reach the required value with another 17 s engine operation. Therefore, the designed control reconfiguration strategy can deal with the thrust loss fault with high practicability and can be applied to real-time FTC systems. Last but not least, conclusions and prospects are presented to inspire researchers with further exploration in this field.

/pdf/autonomous-attitude-reconstruction-analysis-for-propulsion-1aycewc3.pdf

Changlin Xie

Papers

Highly sensitive, sub-microsecond polymer photodetectors for blood oxygen saturation testing

Autonomous Attitude Reconstruction Analysis for Propulsion System with Typical Thrust Drop Fault