Photoluminescence and Photoconductivity of Lead Halide Perovskite Films Modified with Mixed Cellulose Esters-=SUP=-1-=/SUP=-

We have investigated the photoluminescence (PL) and photoconductivity of lead halide perovskite (CH3NH3PbBr3) films modified with different mixed cellulose esters (CEs). It was shown that the absorbance and PL spectra of CH3NH3PbBr3 : CE films contain contributions of both the CH3NH3PbBr3 and CE with the dominant contribution to the PL from perovskite component. The dependences of the integral PL intensities of the CH3NH3PbBr3 : CE films on the optical excitation power turned out to be sublinear. This indicates that exciton recombination, as well as recombination via impurity levels, occur in CH3NH3PbBr3 : CE films at high excitation power levels. The conductivity of CH3NH3PbBr3 : CE films at 300 K increases up to ~90 times when illuminated by a solar simulator, and this effect is environmentally stable due to the formation of hydrogen bonds between CE and the lead halide perovskite CH3NH3PbBr3. It is expected that appropriate selection of CE and optimization of CE inclusion will improve the optoelectronic properties and stability of composite films based on lead halide perovskite-CE composites.

Фотоэлектрические свойства композитных пленок на основе металлоорганического перовскита CH-=SUB=-3-=/SUB=-NH-=SUB=-3-=/SUB=-PbBr-=SUB=-3-=/SUB=- модифицированного смешанным эфиром целлюлозы

It is shown that the introduction of a mixed cellulose esters with acetrimethyl acetate into films of organometallic perovskite CH3NH3PbBr3 significantly increases their stability while maintaining the optical and photoelectric properties of perovskite. It was found that with the introduction of 10-20 wt% mixed cellulose ester in CH3NH3PbBr3, the resistivity of the composite increases by 5-10 times within 60-70 days, while in pure perovskite films such changes are observed within 10-15 days. When the films are irradiated with a simulated sunlight, the resistance of the samples drops by 2-3 orders of magnitude, and the effect of photosensitivity persist for more than 2 months. The formation of hydrogen bonds between mixed cellulose ester and organometallic perovskite is, in our opinion, the main factor that increases the stability of the composite film in comparison with pure perovskite. The investigated composite films are promising for the design of degradation-resistant perovskite solar cells and light-emitting diodes.

Терагерцевое поглощение в композитных пленках на основе металлоорганического перовскита и смешанного эфира целлюлозы

Composites based on the organometallic perovskite CH3NH3PbI3 and mixed cellulose ester were studied by terahertz time-domain spectroscopy. It is shown that the introduction of mixed cellulose esters into the precursor of organometallic perovskite CH3NH3PbI3 significantly modifies the parameters of perovskite in the terahertz region and also improves the stability of such composite films. It is found that the addition of mixed cellulose ester to the perovskite film leads to a significant weakening of the THz absorption bands in the frequency range of the order of 1 and 2 THz, which are caused by the excitation of low-frequency vibrational modes in CH3NH3PbI3 perovskite molecules. This can be explained by the fact that cellulose ester molecules enveloping perovskite molecules dampen low-frequency vibrations in them.

Case Study on Risk Evaluation of Silver Nanoparticle Exposure from Antibacterial Sprays Containing Silver Nanoparticles

This study evaluated the risk of silver nanoparticle (AgNP) exposure from antibacterial sprays containing AgNPs. Using an exposure simulation chamber as the setting for the experiment, various instruments, including a scanning mobility particle sizer (SMPS), condensation particle counter (CPC), dust monitor, and mixed cellulose esters (MCE) filters, are connected to the chamber to measure the exposure levels of AgNPs when using the sprays. To assess potential risks to consumers, margin of exposure (MOE) approach was used to assess risk in which a calculated MOE was compared with a target MOE. When evaluating the risk of antibacterial sprays to inhalation exposure using the MOE, spraying a whole can and spraying an air conditioner both resulted in a high-risk concern level with a MOE ranging from 59 to 146 that was much lower than the no-risk concern level of 1000, while some spray showed a MOE 2049 with no-risk concern level. The dermal exposure levels with a single layer of clothing were estimated at 2–50 μg/kg/day with a MOE ranging from 20,000 to 500,000. Therefore, the current results showed the possibility of high-risk inhalation exposure to AgNPs released when using antibacterial sprays.