The development of Formamidinium lead Iodide based Perovskite Solar Cells: Efficiency and Stability

Perovskite materials have been particularly eye-catching by virtue of its excellent properties, such as high light absorption coefficient, long carrier lifetime, low exciton binding energy and bipolarity transmission, etc. Limited...

The optical properties and in-situ observational evidence for the formation of brown carbon in cloud

Atmospheric brown carbon (BrC) makes a substantial contribution to aerosol light-absorbing and thus the global radiative forcing. Although BrC may change the lifetime of the cloud and ultimately affect precipitation, little is known regarding the optical properties and formation of BrC in the cloud. In the present study, the light-absorption properties of cloud droplet residual (cloud RES) were measured by coupled a ground-based counterflow virtual impactor (GCVI) and an Aethalometer (AE-33), in addition to the cloud interstitial (cloud INT) and ambient (cloud-free) particles by PM2.5 inlet-AE-33, at Mt. Tianjing (1690 m a.s.l.), a remote mountain site in southern China, from November to December 2020. Meanwhile, the light-absorption and fluorescence properties of water-soluble organic carbon (WSOC) in the collected cloud water and PM2.5 samples were also obtained, associated with the concentration of water-soluble ions. The mean light-absorption coefficient (Abs370) of the cloud RES, cloud INT, and cloud-free particles were 0.25 ± 0.15, 1.16 ± 1.14, and 1.47 ± 1.23 Mm−1, respectively. The Abs365 of WSOC was 0.11 ± 0.08 Mm−1 in cloud water and 0.40 ± 0.31 Mm−1 in PM2.5, and the corresponding mass absorption efficiency (MAE365) was 0.17 ± 0.07 and 0.31 ± 0.21 m2·g−1, respectively. A comparison of the light-absorption coefficient between BrC in the cloud RES/cloud INT and WSOC in cloud water/PM2.5 indicates a considerable contribution (48–75 %) of water-insoluble BrC to total BrC light-absorption. Secondary BrC estimated by minimum R squared (MRS) method dominated the total BrC in cloud RES (67–85 %), rather than in the cloud-free (11–16 %) and cloud INT (9–23 %) particles. It may indicate the formation of secondary BrC during cloud processing. Supporting evidence includes the enhanced WSOC and dominant contribution of secondary formation/biomass burning factor (> 80 %) to Abs365 in cloud water provided by Positive Matrix Factorization (PMF) analysis. In addition, we showed that the light-absorption of BrC in cloud water was closely related to humic-like substances and tyrosine/proteins-like substances (r > 0.63, p < 0.01), whereas only humic-like substances for PM2.5, as identified by excitation-emission matrix fluorescence spectroscopy.

ON THE THEORY OF ONE-PHOTON ABSORPTION OF POLARIZED LIGHT IN NARROW-GAP CRYSTALS. EXCLUDING THE EFFECT OF COHERENT SATURATION

In this work, from a microscopic point of view, the linear-circular dichroism of one-photon between band absorption of light in the Kane approximation in narrow-gap crystals is investigated. The matrix elements of onephoton interband optical transitions and the spectral dependence of the light absorption coefficient are calculated.

ON THE THEORY OF ONE-PHOTON ABSORPTION OF POLARIZED LIGHT IN NARROW-GAP CRYSTALS. TAKING INTO ACCOUNT THE EFFECT OF COHERENT SATURATION

In the article, from a microscopic point of view, the linear-circular dichroism of one-photon between band absorption of light in the Kane approximation in narrow-gap crystals is investigated. The linear-circular dichroism of one-photon absorption of polarized light is calculated taking into account the effect of coherent saturation in photoexcited charge carriers. The matrix elements of one-photon interband optical transitions and the corresponding linear-circular dichroism and the spectral dependence of the light absorption coefficient are calculated.

Spectral bio-optical properties of water of Atlantic sector of Antarctic

Studies of variability of spectral bio-optical properties of water of Atlantic sector of Antarctic were carried out during the 79th cruise of the RV “Akademik Mstislav Keldysh” (11.01.2020–04.02.2020). Chlorophyll a and phaeopigment concentration varied in the layer studied from 0.1 to 1.8 mg·m−3, except for two stations with content reaching 2.2 and 4.4 mg·m−3. The relationship was revealed between light absorption coefficient by phytoplankton and chlorophyll a concentration at a wavelength, corresponding to spectrum maxima: aph(438) = 0.044 × Ca1.2, r2 = 0.84 (n = 117); aph(678) = 0.021 × Ca1.1, r2 = 0.89 (n = 117). Spectral distribution of light absorption coefficient by non-algal particles and colored dissolved organic matter was described by exponential function. Absorption parameterization coefficients were retrieved: (1) light absorption coefficient by non-algal particles (0.001–0.027 m−1) and by colored dissolved organic matter (0.016–0.19 m−1) at a wavelength of 438 nm; (2) spectral slope coefficients of these components (0.005–0.016 and 0.009–0.022 nm−1, respectively).

Performance of Optical Coupling Materials in Scintillation Detectors Post Temperature Exposure

In this paper, the room-temperature performance of different optical coupling materials post temperature exposure was tested. The tested couplers included OC431A-LVP, OG0010 optical grease, BLUESIL V-788, and SAINT-GOBAIN BC-630. This was done by subjecting the whole detector with newly applied optical coupling materials to a 2-h temperature exposure—ranging from −20 to 50 °C and then by letting it return to room temperature before collecting a spectrum from a Cs-137 source. The energy resolution at 662 keV was computed as the metric for evaluating the performance. Three trials were run at each coupler–temperature combination. Our results reveal that the performance of all coupling agents do indeed change with temperature after the 2-h exposure. Over all the tested temperature trials, the energy resolution ranged from 11.4 to 14.3% for OC431A-LVP; 10.2 to 14.6% for OG0010; 10 to 13.4% for BLUESIL V-788; and 9.8 to 13.3% for SAINT-GOBAIN BC-630. OC431A-LVP had the lowest variance over the full range, while BC-630 was the most constant for temperatures above 20 °C. Ultraviolet-visible (UV-Vis) spectra experiments were also performed on isolated optical coupling materials to measure the light absorption coefficient. The results show that the temperature-induced variance in light absorption coefficient of each optical coupling materials is one of the reasons for the variance in energy resolution performance. Our findings suggest the need for further investigation into this effect and the recommendation that optical coupling materials need to be selected for the task at hand with greater scrutiny.

Determination of black carbon mass concentration from aerosol light absorption using variable mass absorption cross-section

Atmospheric black carbon (BC) is the strongest visible solar radiative absorber in the atmosphere, exerting significant influences on the earth’s radiation budget. The mass absorption cross-section (MAC) is a crucial parameter for converting light absorption coefficient (bab) to mass equivalent BC concentration (mBC). Traditional filter-based instrument, such as AE33, uses a constant MAC of 7.77 m2/g to derive mBC, which may lead to uncertainty in mBC. In this paper, a new method of converting light absorption coefficient to BC mass concentration is proposed by incorporating the variations of MAC attributed to the influences of aerosol coating state. Mie simulation showed that MAC varied dramatically with different core-shell structures. We compared our new method with traditional method during a field measurement at a site of North China Plain. The results showed that the MAC was smaller (larger) than 7.77 m2/g for particle smaller (larger) than 280 nm, resulting in BC mass size distribution derived from new method was higher (lower) than traditional method for particle smaller (larger) than 280 nm. Size-integrated BC mass concentration derived from new method was 16 % higher than traditional method. Sensitivity analysis indicated that the uncertainty in mBC caused by refractive index (RI) was with in 35 % and the imaginary part of RI had dominant influence on the derived mBC. This study emphasizes the necessity to take variations of MAC into account when deriving mBC from bab and can help constrain the uncertainty in mBC measurements.

The Effect of Carbon Defects in the Coal–Pyrite Vacancy on the Electronic Structure and Optical Properties: A DFT + U Study

Pyrite is a mineral often associated with coal in coal seams and is a major source of sulfur in coal. Coal–pyrite is widely distributed, easily available, low-cost, and non-toxic, and has high light absorption coefficient. So, it shows potential for various applications. In this paper, the density-functional theory (DFT + U) is used to construct coal–pyrite with carbon doped in the sulfur and iron vacancies of pyrite. The effects of different carbon defects, different carbon doping concentrations, and different doping distributions in the same concentration on the electronic structure and optical properties of coal–pyrite were studied. The results show that the absorption coefficient and reflectivity of coal–pyrite, when its carbon atom substitutes the iron and sulfur atoms in the sulfur and iron vacancies, are significantly higher than those of the perfect pyrite, indicating that coal–pyrite has potential for application in the field of photovoltaic materials. When carbon is doped in the sulfur vacancy, this impurity state reduces the width of the forbidden band; with the increase in the doping concentration, the width of the forbidden band decreases and the visible-light absorption coefficient increases. The distribution of carbon impurities impacts the band gap but has almost no effect on the light absorption coefficient, complex dielectric function, and reflectivity, indicating that the application of coal–pyrite to photovoltaic materials should mainly consider the carbon doping concentration instead of the distribution of carbon impurities. The research results provide a theoretical reference for the application of coal–pyrite in the field of photoelectric materials.

Оптические свойства легированных нанопроволок во внешних электрическом и магнитном поляx

The impurity absorption of light in quantum wires in the presence of external electric and magnetic fields directed parallel to each other and perpendicular to the axis of the nanowire is studied theoretically. Impurities doped in a quantum wire are modeled by a zero-range potential. Expressions are obtained for the light absorption coefficient and the features of impurity absorption of light are studied for all possible directions of polarization of the light wave. In particular, in the presence of external fields, some optical transitions, which are forbidden in the absence of fields, become allowed. The frequency dependences of the light absorption coefficient and the influence of electric and magnetic fields on the value of the impurity light absorption coefficient are investigated. The possibility of controlling the optical characteristics of nanowires using an electric field is shown.