Pressure and temperature dependencies of the Gunn and lasing thresholds in (GaIn) (AsP) semiconductor devices.

16 cm-3 n-doped LPE grownGaxIn1-xAsyP1-y samples are presented as a function of temperature, pressure and alloy composition. The threshold field and peak velocities measured across the alloy agreed with measurements made by Marsh, confirming that GalnAs is the most attractive composition for high speed microwave devices. Devices made from mid alloy material benefit from a low temperature sensitivity of the threshold current, which is less than half the sensitivity of GaAs devices. The results imply that alloy scattering remains influential even at high fields. In agreement with pressure measurements on InP and GaAs the threshold field increased with pressure primarily because of the increase in the electron effective mass. The experimental results are compared with Monte Carlo simulations for quaternary alloy compositions y=O, 0.5 and 1.0. The effect of alloy scattering on the high field measurements is discussed. High pressure studies on 1.3 and 1.55mum GalnAsP lasers were performed in order to investigate the cause of the high temperature sensitivity of the threshold current. Threshold current, spontaneous carrier lifetime and operating wavelength measurements versus pressure revealed that intervalence band absorption (IVBA) is the dominant loss mechanism at room temperature in the 1.55mum lasers. In 1.3mum lasers both IVBA and the CHHS Auger process are important processes at room temperature, the Auger process is probably the more dominant of the two. At room temperature neither carrier loss over the barrier nor the CHCC Auger process is dominant in 1.3mum or 1.55mum lasers. Carrier leakage from the active layer has been modelled theoretically using Monte Carlo simulation. Hot holes created via the CHHS Auger and IVBA processes are believed to be responsible for hole leakage to the n-InP confinement layer

Radiation Hardness of Perovskite Solar Cells Based on Aluminum‐Doped Zinc Oxide Electrode Under Proton Irradiation

Due to their high specific power and potential to save both weight and stow volume, perovskite solar cells have gained increasing interest to be used for space applications. However, before they can be deployed into space, their resistance to ionizing radiations such as high‐energy protons must be demonstrated. In this report, we investigate the effect of 150 keV protons on the performance of perovskite solar cells based on aluminium‐doped zinc oxide (AZO) transparent conducting oxide (TCO). Record power conversion efficiency of 15% and 13.6% were obtained for cells based on AZO under AM1.5G and AM0 illumination, respectively. We demonstrate that perovskite solar cells can withstand proton irradiation up to 1013 protons.cm−2 without significant loss in efficiency. At this irradiation dose, Si or GaAs solar cells would be completely or severely degraded when exposed to 150 keV protons. From 1014 protons.cm−2, a decrease in short‐circuit current of the perovskite cells is observed, which is consistent with interfacial degradation due to deterioration of the Spiro‐OMeTAD HTL during proton irradiation. Using a combination of non‐destructive characterization techniques, results suggest that the structural and optical properties of perovskite remain intact up to high fluence levels. Although shallow trap states are induced by proton irradiation in perovskite bulk at low fluence levels, they can release charges efficiently and are not detrimental to the cell's performance. This work highlights the potential of perovskite solar cells based on AZO TCO to be used for space applications and give a deeper understanding of interfacial degradation due to proton irradiation

Characterization of stability of benchmark organic photovoltaic films after proton and electron bombardments

Organic solar cells have attractive potential for space applications as they have very high specific power (power generated per weight) and ultra-high flexibility (to reduce stowed volume). However, one critical issue is whether they are stable under the harsh space environment, particularly their stability under high energy, high flux, electron and proton bombardment. In this paper, the stability of benchmark organic photovoltaic layers under proton bombardment (150 keV with a fluence of 1 × 1012/cm2) and electron bombardment (1 MeV with a fluence of 1 × 1013/cm2) under vacuum is investigated. Raman spectroscopy, photoluminescence spectroscopy, and optical reflectance spectroscopy are applied to study their chemical/structural, photo-chemical/morphological, and optical stability after the bombardments. The results show that all the benchmark organic photovoltaic films are stable under the radiation, implying that organic solar cells could be feasible for space applications

Proton Radiation Hardness of Perovskite Solar Cells Utilizing a Mesoporous Carbon Electrode

Funder: Airbus Endeavr WalesFunder: Alexander von Humboldt FoundationWhen designing spacefaring vehicles and orbital instrumentation, the onboard systems such as microelectronics and solar cells require shielding to protect them from degradation brought on by collisions with high‐energy particles. Perovskite solar cells (PSCs) have been shown to be much more radiation stable than Si and GaAs devices, while also providing the ability to be fabricated on flexible substrates. However, even PSCs have their limits, with higher fluences being a cause of degradation. Herein, a novel solution utilizing a screen‐printed, mesoporous carbon electrode to act bi‐functionally as an encapsulate and the electrode is presented. It is demonstrated that the carbon electrode PSCs can withstand proton irradiation up to 1 × 1015 protons cm−2 at 150 KeV with negligible losses (<0.07%) in power conversion efficiency. The 12 μm thick electrode acts as efficient shielding for the perovskite embedded in the mesoporous TiO2. Through Raman and photoluminescence spectroscopy, results suggest that the structural properties of the perovskite and carbon remain intact. Simulations of the device structure show that superior radiation protection comes in conjunction with good device performance. This work highlights the potential of using a carbon electrode for future space electronics which is not limited to only solar cells

Pressure and temperature dependencies of the Gunn and lasing thresholds in (GaIn) (AsP) semiconductor devices.

16 cm-3 n-doped LPE grownGaxIn1-xAsyP1-y samples are presented as a function of temperature, pressure and alloy composition. The threshold field and peak velocities measured across the alloy agreed with measurements made by Marsh, confirming that GalnAs is the most attractive composition for high speed microwave devices. Devices made from mid alloy material benefit from a low temperature sensitivity of the threshold current, which is less than half the sensitivity of GaAs devices. The results imply that alloy scattering remains influential even at high fields. In agreement with pressure measurements on InP and GaAs the threshold field increased with pressure primarily because of the increase in the electron effective mass. The experimental results are compared with Monte Carlo simulations for quaternary alloy compositions y=O, 0.5 and 1.0. The effect of alloy scattering on the high field measurements is discussed. High pressure studies on 1.3 and 1.55mum GalnAsP lasers were performed in order to investigate the cause of the high temperature sensitivity of the threshold current. Threshold current, spontaneous carrier lifetime and operating wavelength measurements versus pressure revealed that intervalence band absorption (IVBA) is the dominant loss mechanism at room temperature in the 1.55mum lasers. In 1.3mum lasers both IVBA and the CHHS Auger process are important processes at room temperature, the Auger process is probably the more dominant of the two. At room temperature neither carrier loss over the barrier nor the CHCC Auger process is dominant in 1.3mum or 1.55mum lasers. Carrier leakage from the active layer has been modelled theoretically using Monte Carlo simulation. Hot holes created via the CHHS Auger and IVBA processes are believed to be responsible for hole leakage to the n-InP confinement layer

The RhoA Activator GEF-H1/Lfc Is a Transforming Growth Factor-β Target Gene and Effector That Regulates α-Smooth Muscle Actin Expression and Cell Migration

TGFβ induces various responses, including Rho signaling. How TGFβ stimulates Rho is poorly understood. Our data indicate that GEF-H1 is a target and effector of TGFβ to regulate Rho signaling, gene expression, and cell migration, suggesting that it represents a new marker and possible therapeutic target for degenerative and fibrotic diseases