Phenomenological morphology design of hybrid organic-inorganic perovskite solar cell for high efficiency and less hysteresis

In this report, a modeling approach is employed to study the effect of the grain boundaries (GBs) and their electronic activity on the performance parameters of the perovskite solar cells (PSCs). Our model is based on the 1- dimensional drift-diffusion framework to engage the electron (hole) defects formed in the GBs and the GB's location through the perovskite layer. Power conversion efficiency (PCE) of the PSC is optimized with regards to the perovskite layer thickness, GBs location and perovskite layer band offset with GBs layer. The results shows that the location or the distribution of the GBs can vary the PCE of PSCs from 12% to around 21%, thereby making proper morphology engineering and passivation of GBs is a chief requirement for achieving high efficiency. PCEs larger than 21% require GB defect densities below 10(15) cm(-2). It is demonstrated that the band offset of about 100 meV with GB width of 1 nm could effectively suppress the negative impact of the GBs throughout the entire perovskite layer. Interestingly, GBs location at closer points to electron transport layer (ETL)/perovskite interface may give rise to higher PCEs, however, relatively stronger hysteresis in current values is observed. The results here provide insight into the effect of the GBs location and their corresponding type of defects on the hysteresis and the PSC performance and opens up new horizons to find solutions for current PSC's shortcomings

Ultra-High Precision Radiation Dosimetry via Laser Bleaching the Color Centers in Fast Recovery Optical Fiber Sensors

High energy electromagnetic radiation or heavy charged particles are extensively used for medical treatment of certain cancers. Precise prediction or measurements of energy deposition of any types of radiation on tissue is critical in radiation therapy. In this research, the sensitivity of optical fiber dosimeters specifically doped with phosphor (P), Germanium (Ge) and Erbium (Er) are analyzed using Co-60 source at 169 cGy/min. The sensors are calibrated and the values of radiation induced attenuation (RIA) are evaluated at different temperatures. Nondestructive method of laser bleaching is shown superior to thermal bleaching for sensor recovery. The error in P- doped and Er- doped fiber sensors are estimated to be 6 and 4%, respectively. The fastest recovery is assigned to Er- doped fiber. The results show that Er- doped optical fiber sensor can perform ultrahigh sensitive low dosimetry of gamma- ray for medical application. The results of the present work can provide implications for further enhancement of radiation sensing for real- time dosimetry

ZnO-SrAl2O4:Eu Nanocomposite-Based Optical Sensors for Luminescence Thermometry

Conventional thermometers fail to operate in a variety of medical procedures due to the harsh and sensitive environments required for such applications, and therefore, the development of optical fiber thermometers has gained significant attention. In this study, a ZnO-SrAl2O4:Eu (ZnO-SAO:Eu) nanocomposite has been synthesized by using a CO2 laser, which showed enhanced optical properties and a dynamic range in comparison with the crystalline ones. XRD, EDAX, SEM, and PL spectroscopy investigated the crystalline and optical properties of precursors, and the final nanostructure, and the findings were in agreement with references. Further analysis of the PL spectra in a 0-100 degrees C range suggests that the optical properties of the ZnO-SAO:Eu nanocomposite show a linear behavior toward temperature alterations. Considering this inter-relation and measuring the decay time for various frequencies helped us calibrate the temperature based on phase angle shift alterations. The curve obtained at 30 Hz frequency exhibits the highest linearity and accuracy (0.33%) due to its relatively high phase shift (60 degrees C) in the studied temperature range. The fabricated sensor exhibited great sensitivity and repeatability while maintaining an unprecedented structure. Finally, the thermometer's applicability for future industries was tested by measuring the interior temperature of a dead muscle tissue as it was being heated by a diode laser and it was accompanied by remarkable results. This achievement could make this device a promising addition to the drug delivery science and industry as it could aid the study and optimization of medications that increase the targeted tissues temperature and therefore can be employed in treating tumors that are formed in organic tissues