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Rapid monitoring of carbon monoxide (CO) is crucial because of its detrimental effects on human health and other living organisms. Metal oxide semiconductor (MOS) nanostructures are identified as promising materials for gas sensors, but they have several limitations, such as inadequate selectivity, high operating temperature, and substantial power consumption. This article presents the design, simulation, and evaluation of a CO gas sensor that utilizes silver-loaded zinc oxide/reduced graphene oxide (ZnO/rGO). Operating conditions for the sensor have been optimized for high performance and fast response/recovery times. An optimized load of 1.5 wt.% of Ag into ZnO/rGO with a weight ratio of 2:1 allows the sensor to detect CO with a response magnitude of 6.26 even at a temperature as low as $30~^{\circ }$ C. Furthermore, it shows a response time of 25 s and a recovery time of 49 s when exposed to a CO concentration of 30 ppm. The incorporation of 1.5 wt.% Ag into ZnO/rGO also improves its selectivity toward CO against various interfering gases. The improvement in sensor performance is attributed to the high surface area of rGO, which promotes the adsorption of CO gas molecules and the catalytic effect of Ag content which reduces the activation energy. The simulation result agrees well with the experimental data, demonstrating superior sensitivity at low temperatures. This research can facilitate identifying appropriate sensing materials and optimal designs for high-performance gas sensors and forecast their behavior before the fabrication process begins.

Description: In this review, we have highlighted recent developments in one-dimensional electron transport materials for perovskite solar cells. The potential strategies to further boost device performance are also discussed.

Electron- and hole-current in forward and reverse scans manifest severe hysteresis during space-charge-limited-current measurements, which causes significant differences in the extracted values of carrier transport properties in forward and reverse scans.

All-inorganic perovskite solar cells (IPSCs) have gained massive attention due to their less instability against common degradation factors (light, heat, and moisture) than their organic–inorganic hybrid counterparts. Inorganic perovskites bear a general formula of CsPbX3(X = Cl, I, Br). The mixed halide CsPbIBr2perovskite possesses an intermediate band gap of 2.03 eV with enhanced stability, which is still available for photovoltaic applications and the research focus of this work. We present a synergistic approach of pre-heated solution dropping with inorganic additive inclusion to deposit the organic-free triple anion CsPbIBr2PSC. Erbium (Er)-passivated triple-anion CsI(PbBr2)0.97(ErCl3)0.03IPSCs with inorganic carrier selective layers (CTLs), that is, organic-free, are fabricated with enhanced carrier diffusion length and crystalline grain size while lessening the grain boundaries near perovskite active layer (PAL)-bulk/carrier selective interfaces. As a result, the trap-state densities within the perovskite bulk were suppressed with stabilized CTL/PAL interfaces for smooth and enhanced carrier transportation. Therefore, for the first time, we contradict the common belief of VOCloss due to halide segregation, as a nice VOCof about 1.34 V is achieved for an organic-free IPSC through enriching initial radiative efficiency, even when halide segregation is present. The optimized organic-free IPSC yielded a power conversion efficiency of 11.61% and a stabilized power output of 10.72%, which provides the potential opportunity to integrate into agrivoltaics (AgV) projects.

A water-stable thin film composed of C6H4NH2CuCl2I was fabricated using spin-coating precursor solutions that dissolved equimolar amounts of C6H4NH2I and CuCl2in N,N-dimethylformamide. Photoelectrochemical characteristics show that the C6H4NH2CuCl2I film demonstrated a stable photocurrent (∼1 μA/cm2) in an aqueous solution under white light (11.5 mW/cm2) even after 3000 s, while exhibiting a photon-to-current efficiency of 0.093% under AM1.5 (100 mW/cm2) illumination. However, these values were significantly lower than those of the CH3NH3PbX3(X = I, Cl) film in solid devices. The electron diffusion length L(e–) (373 nm) and hole diffusion length L(h+) (177 nm) in the C6H4NH2CuCl2I photoelectrode were significantly lower than those of CH3NH3PbX3, limiting the photoelectrochemical and photocatalysis performances. Moreover, L(h+) was shorter than L(e–) in the C6H4NH2CuCl2I photoelectrode, resulting in the hole-collecting efficiency [ηc(h+)] being lower than the electron-collecting efficiency [ηc(e–)]. A CuO interlayer was introduced as a hole transport layer for the C6H4NH2CuCl2I photoelectrode, which improved L(h+) and ηc(h+).

Perovskites have been unprecedented with a relatively sharp rise in power conversion efficiency in the last decade. However, the polycrystalline nature of the perovskite film makes it susceptible to surface and grain boundary defects, which significantly impedes its potential performance. Passivation of these defects has been an effective approach to further improve the photovoltaic performance of the perovskite solar cells. Here, we report the use of a novel hydrazine-based aromatic iodide salt or phenyl hydrazinium iodide (PHI) for secondary post treatment to passivate surface and grain boundary defects in triple cation mixed halide perovskite films. In particular, the PHI post treatment reduced current at the grain boundaries, facilitated an electron barrier, and reduced trap state density, indicating suppression of leakage pathways and charge recombination, thus passivating the grain boundaries. As a result, a significant enhancement in power conversion efficiency to 20.6% was obtained for the PHI-treated perovskite device in comparison to a control device with 17.4%.

The combination of organic ligands and inorganic Pb–I frameworks in layered perovskites has bestowed upon them high structural tunability and stability, while their microscopic degradation mechanism remains unclear. Here, we found the key role of ligands in intrinsic structural stability and the consequent morphological evolution in layered perovskites during long-term ambient aging based on (GA)(MA)nPbnI3n+1(GA = guanidinium, = 4) and (BDA)(MA)n−1PbnI3n+1(BDA = 1,4-butanediammonium, < n> = 4) perovskites. The BDA-based perovskites have a low intrinsic stability due to high crystal formation energy (ΔH), which are prone to hydration during ambient aging. We overserved changed crystal orientation from perpendicular to parallel, a delayed charge populating time from <1 ps to >50 ps, an inhibited carrier transfer kinetics between quantum wells, an increase of 0.9 μs of charge carrier transport time and a decrease of 1.2 μs of charge carrier lifetime in the BDA-based film during ambient aging, which accounts for a large power-conversion efficiency (PCE) loss (14.2% vs 11.2%). By contrast, the GA ligand increases the intrinsic structural stability of perovskites, which not only yields an initial PCE as high as 20.0% but also helps retain excellent optoelectronic properties during aging. Therefore, only a slight PCE loss (20.0% vs 19.1%) was observed. Our work reveals the key role of organic–inorganic interaction affecting the intrinsic structural stability and optoelectronic properties, and provides a theoretical basis for the future design of stable and efficient optoelectronic devices.