Role of additives and surface passivation on the performance of perovskite solar cells

Outstanding improvement in power conversion efficiency (PCE) over 25% in a very short period and promising research developments to reach the theoretical PCE limit of single junction solar cells, 33%, enables organic–inorganic perovskite solar cells (OIPSCs) to gain much attention in the scientific and industrial community. The simplicity of production of OIPSCs from precursor solution either on rigid or flexible substrates makes them even more attractive for low-cost roll-to-roll production processes. Though OIPSCs show as such higher PCE with simple solution processing methods, there are still unresolved issues, while attempts are made to commercialize these solar cells. Among the major problems is the instability of the photoactive layer of OIPSCs at the interface of the charge transport layers and /or electrodes during prolonged exposure to moisture, heat and radiation. To achieve matched PCE and stability, several techniques such as molecular and interfacial engineering of components in OIPSCs have been applied. Moreover, in recent times, engineering on additives, solvents, surface passivation, and structural tuning have been developed to reduce defects and large grain boundaries from the surface and/or interface of organic–inorganic perovskite films. Under this review, we have shown recently developed additives and passivation strategies, which are strongly focused to enhance PCE and long-term stability simultaneously.

Passive solar house prototype design with a new bio-based material for a semi-arid climate

In this study, a passive solar house prototype was built using Trombe wall and was tested in the semi-arid region of Batna, in eastern Algeria. Traditional local materials (stone and adobe) were used for the construction of the thermal storage wall. A new local bio-based material made from date palm trunks was used for the insulation of the passive house prototype. For a better understanding of passive house heating and for a comparative study, a numerical simulation, using Fluent, was carried out. The aim of this study was to supply recommendations for improving the passive systems and to participate to the energy consumption control in the building sector. The results show that the experimental and numerical simulation results are in good agreement. The optimal orientation of the solar passive house has been determined, which is at 160° southeast. The use of local and bio-based materials has proven its effectiveness in the construction of the passive house. The thermal behavior of date palm wood has been found to be close to those of insulation materials commonly used in buildings. That means it has the same thermal insulation ability (thermal conductivity). On the other hand, the results show that the thermal efficiency of the passive solar heating system, with an adobe wall is significantly higher (50%) than that with a stone wall (30.7%).

Preparation, characterization and evaluation of x-MoO3/Al-SBA-15 catalysts for biodiesel production

Biodiesel is an alternative source of renewable energy that can be produced by a transesterification of vegetable oils. Mesoporous molecular sieves, such as SBA-15, due to high surface area and thermal stability are promising precursors for heterogeneous catalysts in the transesterification reaction. In this work, Al-SBA-15 precursor was obtained by direct hydrothermal synthesis, impregnated with different MoO3 contents (5, 10 and 15 wt%) by the pore saturation method, and evaluated as heterogeneous catalyst in the production of biodiesel from a transesterification of soybean oil with methanol. Al-SBA-15 precursor as well as MoO3/Al-SBA-15 catalyst were characterized for its structural characteristic by X-ray diffraction, textural characteristic by N2 adsorption analysis, and thermal stability by thermogravimetric analysis. An experimental planning 22 + 3 CtPt was used to evaluate the influence of MoO3 content and reaction time on biodiesel yield from soybean oil and methanol. The biodiesel content in the final product was obtained by gas chromatography. An average biodiesel yield of 96% was obtained with the catalyst 10%MoO3/Al-SBA-15 under the following reaction conditions: 20:1 methanol/soybean oil molar ratio, and 3 wt% of catalyst loading at 150 °C in 3 h. After five consecutive reaction cycles, the biodiesel yield decreased by about 34%. The density and acidity of the biodiesel produced are within the specified values for commercialization according to international standards. Graphical abstract

Oxygen (O2) reduction reaction on Ba-doped LaMnO3 cathodes in solid oxide fuel cells: a density functional theory study

The oxygen adsorption and subsequent reduction on the {100} and {110} surfaces of 25% Ba-doped LaMnO3 (LBM25) have been studied at the density functional theory (DFT) with Hubbard correction and the results compared with adsorption on 25% Ca-doped LaMnO3 (LCM25) and Sr-doped LaMnO3 (LSM25). The trend in the reduction energies at the Mn cation sites are predicted to be in the order LSM25 < LBM25 < LCM25. In addition, the trend in dissociation energies for the most exothermic dissociated precursors follow the order LBM25 < LSM25 < LCM25. The adsorption energies (− 2.14 to − 2.41 eV) calculated for the molecular O2 precursors at the Mn cation sites of LCM25, LSM25 and LBM25 are thermodynamically stable, when compared directly with the adsorption energies (Eads = − 0.56 to − 1.67 eV) reported for the stable molecular O2 precursors on the Pt, Ni, Pd, Cu and Ir {111} surfaces. The predicted Gibbs energies as a function of temperature (T = 500–1100 °C) and pressures (p = 0.2 atm) for the adsorption and dissociation on the surfaces were negative, an indication of the feasibility of oxygen reduction reaction on the {100} and {110} surfaces at typical operating temperatures reported in this work.

Efficient photocatalytic hydrogen production over Ce/ZnO from aqueous methanol solution

Ce/ZnO crystallites along with bare ZnO were prepared by solution free mechanochemical method and characterized with powder XRD, SEM, EDX, XPS, UV–Visible and Photoluminescence (PL) spectra. The visible light photocatalytic performance of these materials was investigated for H2 evolution with the aqueous 10vol% methanol solution under one sun conditions using solar simulator. X-ray diffraction data suggests the hexagonal wurtzite structure for Ce/ZnO crystallites and the incorporation of Ce4+ ion in ZnO is supported by the shifting of XRD peaks to lower Bragg angles that indicate lattice expansion. With the increase of Ce content in ZnO, the crystallite size of Ce/ZnO decreases and the specific surface area increases. UV–Visible spectra propose the decrease in optical band gap of Ce incorporated ZnO with the increase of Ce content up to 3 mol. %. The XPS analysis supports the incorporation of Ce4+ in Ce/ZnO. The PL spectra propose that, with the insertion of Ce ions into ZnO, intensity of UV emission band decreases that reflects the low recombination rate of photogenerated charge carriers, which is responsible for higher photocatalytic H2 production. The extent of hydrogen production is affected by calcination temperature of Ce/ZnO. 2 mol. % Ce incorporated ZnO calcined at 600 °C produces43 μmolh−1 g−1 of hydrogen.

Synthesis of activated carbon derived from chicken feather for Li-ion batteries through chemical and physical activation process

The use of activated carbon from biomass as an electrode for lithium-ion batteries is promising because of the low cost, natural abundance, and environmentally friendly. Chicken feather is a biomass that has the potential to be a source of activated carbon, because it contains keratin. The activation process affects the quality of activated carbon, thereby increasing battery performance. In this study, chicken feather waste was chemically activated using KOH and combined with physical activation at temperature variations of 750, 850 and 950 °C. The activation process significantly influenced electrochemical properties because of the difference in their microstructure. The activated carbon pyrolyzed at 850 °C (CFCA-850) shows the highest discharge capacity of 285.78 mAhg−1, good cycling stability and rate performance due to its higher interlayer spacing and large surface area. Furthermore, electronic conductivity and ion increase, thus improve battery performance.

Ambient fabrication of perovskite solar cells through delay-deposition technique

The establishment of perovskite solar cells (PSCs) in terms of their power-conversion efficiency (PCE) over silicon-based solar cells is undeniable. The state-of-art of easy device fabrications of PSCs has enabled them to rapidly gain a place in third-generation photovoltaic technology. Numerous obstacles remain to be addressed in device efficiency and stability. Low performance owing to easily degraded surface and deterioration of perovskite film quality resulting from humidity are issues that often arise. This work explored a new approach to producing high-quality perovskite films prepared under high relative humidity (RH = 40%–50%). In particular, the ubiquitous 4-tert-butylpyridine (tBp) was introduced into lead iodide (PbI2) precursor as an additive, and the films were fabricated using a two-step deposition method followed by a delay-deposition technique of methylammonium iodide (MAI). High crystallinity and controlled nucleation of MAI were needed, and this approach revealed the significance of time control to ensure high-quality films with large grain size, high crystallography, wide coverage on substrate, and precise and evenly coupled MAI molecules to PbI2 films. Compared with the two-step method without time delay, a noticeable improvement in PCE from 3.2 to 8.3% was achieved for the sample prepared with 15 s time delay. This finding was primarily due to the significant enhancement in the open-circuit voltage, short-circuit current, and fill factor of the device. This strategy can effectively improve the morphology and crystallinity of perovskite films, as well as reduce the recombination of photogenerated carriers and increase of current density of devices, thereby achieving improved photovoltaic performance.

Stability, reusability, and equivalent circuit of TiO2/treated metakaolinite-based dye-sensitized solar cell: effect of illumination intensity on Voc and Isc values

In this research, treated metakaolinite (TMK) was introduced into the TiO2 photoelectrode to fabricated dye-sensitized solar cells (DSSCs). The photovoltaic cells have four main natural components, i.e., a photosensitizer (carotenoid bixin), photoelectrode (TiO2/kaolinite), electrolyte (glycerine carbonate derivative), and counter-electrode (carbon). Their stability, reusability, and equivalent circuit were studied. The presence of 5% of TMK in anatase TiO2 paste decreased the TiO2 band gap from 3.21 to 3.16 eV. The result showed that the presence of 5% of TMK in TiO2 paste was more favorable to obtain higher energy conversion efficiency. Under a light intensity of 200 W/m2, it produced an energy conversion yield of 0.086%. The combination of the electrolyte and the TMK demonstrated a synergistic effect to improve the electrical properties of the DSSC. The energy storage function worked well until the third day of analysis. The DSSC based on TiO2/TMK photoelectrode exhibited 16 times better stability than pure TiO2-based photoelectrode. The Faraday charge transfer processes showed that the TiO2/TMK photoelectrode is not in direct contact with the carbon counter-electrode.

Mechanisms of CO2 reduction into CO and formic acid on Fe (100): a DFT study

Understanding the mechanism of CO2 reduction on iron is crucial for the design of more efficient and cheaper iron electrocatalyst for CO2 conversion. In the present study, we have employed spin-polarized density functional theory calculations within the generalized gradient approximation (DFT-GGA) to elucidate the mechanism of CO2 reduction into carbon monoxide and formic acid on the Fe (100) facet. We also sort to understand the transformations of the other isomers of adsorbed CO2 on iron as earlier mechanistic studies are centred on the transformations of the C2v geometry alone and not the other possible conformations i.e., flip-C2v and Cs modes. Two alternative reduction routes were considered i.e., the direct CO2 dissociation against the hydrogen-assisted CO2 transformation through formate and carboxylate into CO and formic acid. Our results show that CO2 in the C2v mode is the precursor to the formation of both products i.e., CO and formic acid. Both the formation and transformation of CO2 in the Cs and flip-C2v is challenging kinetically and thermodynamically compared to the C2v mode. The formic acid formation is favoured over CO via the reverse water gas shift reaction mechanism on Fe (100). Both formic acid formation and CO formation will proceed via the carboxylate intermediate since formate is a stable intermediate whose transformation into formic acid is challenging both kinetically and thermodynamically. Graphic abstract

Ampoule method fabricated sulfur vacancy-rich N-doped ZnS electrodes for ammonia production in alkaline media

The electrochemical production of green and low-cost ammonia requests the development of high-performance electrocatalysts. In this work, the ampoule method was applied to modulate the surface of the zinc electrode by implanting defects and low-valent active sites. The N-doped ZnS electrocatalyst was thus generated by sulfurization with thiourea and applied for electrocatalytic nitrogen reduction reaction (ENRR). Given the rich sulfur vacancies and abundant Zn-N active sites on the surface, excellent catalytic activity and selectivity were obtained, with an NH3 yield rate of 2.42 × 10–10 mol s−1 cm−2 and a Faradaic efficiency of 7.92% at − 0.6 V vs. RHE in 0.1 M KOH solution. Moreover, the as-synthesized zinc electrode exhibits high stability after five recycling tests and a 24 h potentiostatic test. The comparison with Zn foil, non-doping ZnS/Zn and recent metal sulfide electrocatalysts further demonstrated advanced catalytic performance of N@ZnS/Zn for ENRR. By simple synthesis, S vacancies, and N-doping defects, this promising electrocatalyst would represent a good addition to the arena of transition-metal-based catalysts with superior performance in ENRR. Graphic abstract