Synthesis of SnO2 nanofibers and nanobelts electron transporting layer for efficient perovskite solar cells

Tin/Tin Oxide Nanostructures: Formation, Application, and Atomic and Electronic Structure Peculiarities

For a very long period, tin was considered one of the most important metals for humans due to its easy access in nature and abundance of sources. In the past, tin was mainly used to make various utensils and weapons. Today, nanostructured tin and especially its oxide materials have been found to possess many characteristic physical and chemical properties that allow their use as functional materials in various fields such as energy storage, photocatalytic process, gas sensors, and solar cells. This review discusses current methods for the synthesis of Sn/SnO2 composite materials in form of powder or thin film, as well as the application of the most advanced characterization tools based on large-scale synchrotron radiation facilities to study their chemical composition and electronic features. In addition, the applications of Sn/SnO2 composites in various fields are presented in detail.

Metal oxide charge transporting layers for stable high-performance perovskite solar cells

This review summarizes the recent progress in metal oxide charge transporting layers to achieve stable high-performance perovskite solar cells.

g-C3N4-Stabilised Organic–Inorganic Halide Perovskites for Efficient Photocatalytic Selective Oxidation of Benzyl Alcohol

The outstanding optoelectronic performance and facile synthetic approach of metal halide perovskites has inspired additional applications well beyond efficient solar cells and light emitting diodes (LEDs). Herein, we present an alternative option available for the optimisation of selective and efficient oxidation of benzylic alcohols through photocatalysis. The materials engineering of hybrids based on formamidine lead bromide (FAPbBr3) and graphic carbon nitride (g-C3N4) is achieved via facile anti-solvent approach. The photocatalytic performance of the hybrids is highly reliant on weight ratio between FAPbBr3 and g-C3N4. Besides, the presence of g-C3N4 dramatically enhances the long-term stability of the hybrids, compared to metal oxides hybrids. Detailed optical, electrical and thermal studies reveal the proposed novel photocatalytic and stability behaviours arising in FAPbBr3 and g-C3N4 hybrid materials.

Strategies for High-Performance Large-Area Perovskite Solar Cells toward Commercialization

Perovskite solar cells (PSCs) have received a great deal of attention in the science and technology field due to their outstanding power conversion efficiency (PCE), which increased rapidly from 3.9% to 25.5% in less than a decade, comparable to single crystal silicon solar cells. In the past ten years, much progress has been made, e.g. impressive ideas and advanced technologies have been proposed to enlarge PSC efficiency and stability. However, this outstanding progress has always been referred to as small-area (<0.1 cm2) PSCs. Little attention has been paid to the preparation processes and their micro-mechanisms for large-area (>1 cm2) PSCs. Meanwhile, scaling up is an inevitable way for large-scale application of PSCs. Therefore, we firstly summarize the current achievements for high efficiency and stability large-area perovskite solar cells, including precursor composition, deposition, growth control, interface engineering, packaging technology, etc. Then we include a brief discussion and outlook for the future development of large-area PSCs in commercialization.

Red-Carbon-Quantum-Dot-Doped SnO2 Composite with Enhanced Electron Mobility for Efficient and Stable Perovskite Solar Cells

An efficient electron transport layer (ETL) plays a key role in promoting carrier separation and electron extraction in planar perovskite solar cells (PSCs). An effective composite ETL is fabricated using carboxylic-acid- and hydroxyl-rich red-carbon quantum dots (RCQs) to dope low-temperature solution-processed SnO₂ , which dramatically increases its electron mobility by ≈20 times from 9.32 × 10^-4 to 1.73 × 10^-2 cm² V^-1 s^-1 . The mobility achieved is one of the highest reported electron mobilities for modified SnO₂ . Fabricated planar PSCs based on this novel SnO₂ ETL demonstrate an outstanding improvement in efficiency from 19.15% for PSCs without RCQs up to 22.77% and have enhanced long-term stability against humidity, preserving over 95% of the initial efficiency after 1000 h under 40-60% humidity at 25 °C. These significant achievements are solely attributed to the excellent electron mobility of the novel ETL, which is also proven to help the passivation of traps/defects at the ETL/perovskite interface and to promote the formation of highly crystallized perovskite, with an enhanced phase purity and uniformity over a large area. These results demonstrate that inexpensive RCQs are simple but excellent additives for producing efficient ETLs in stable high-performance PSCs as well as other perovskite-based optoelectronics.

Novel 3D hierarchically structured cauliflower-shaped SnO2 nanospheres as effective photoelectrodes in hybrid photovoltaics

Optical and electrical characteristics of wide bandgap metal oxides, namely the charge mobility, bandgap and energy level, directly define the performance and stability of photovoltaics. For the first time, novel three-dimensional (3D) hierarchically structured cauliflower-shaped SnO2 nanospheres with nanorods on their surface were obtained by a simple hydrothermal method without any additives at low temperature. The obtained hierarchically structured SnO2 nanospheres show large specific surface areas, proven to be efficient for sensitizer loading in both perovskite solar cells (PSCs) and dye-sensitized solar cells (DSSCs). The nanospheres could improve light harvesting and also enhance electron transport through the grain boundaries. Ultimately, a maximum power conversion efficiency of 10.37% is obtained for 3D hierarchically structured SnO2 nanosphere-based DSSCs in which SnO2 is used as the scattering layer, and a remarkable efficiency of 20.01% is achieved when 3D hierarchically structured SnO2 nanospheres are employed as the electron transport material in PSCs. We trust that our work provides a new insight into construction and structural design of highly efficient hybrid photovoltaics.

Room-Temperature Sputtered SnO2 as Robust Electron Transport Layer for Air-Stable and Efficient Perovskite Solar Cells on Rigid and Flexible Substrates

Extraordinary photovoltaic performance and intriguing optoelectronic properties of perovskite solar cells (PSCs) have aroused enormous interest from both academic research and photovoltaic (PV) industry. In order to bring PSC technology from laboratory to market, material stability, device flexibility, and scalability are important issues to address for vast production. Nevertheless, PSCs are still primarily prepared by solution methods which limit film scalability, while high-temperature processing of metal oxide electron transport layer (ETL) makes PSCs costly and incompatible with flexible substrates. Here, we demonstrate rarely-reported room-temperature radio frequency (RF) sputtered SnO₂ as a promising ETL with suitable band structure, high transmittance, and excellent stability to replace its solution-processed counterpart. Power conversion efficiencies (PCEs) of 12.82% and 5.88% have been achieved on rigid glass substrate and flexible PEN substrate respectively. The former device retained 93% of its initial PCE after 192-hour exposure in dry air while the latter device maintained over 90% of its initial PCE after 100 consecutive bending cycles. The result is a solid stepping stone toward future PSC all-vapor-deposition fabrication which is being widely used in the PV industry now.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Facile Synthesis of Hierarchical Tin Oxide Nanoflowers with Ultra-High Methanol Gas Sensing at Low Working Temperature

In this work, the hierarchical tin oxide nanoflowers have been successfully synthesized via a simple hydrothermal method followed by calcination. The as-obtained samples were investigated as a kind of gas sensing material candidate for methanol. A series of examinations has been performed to explore the structure, morphology, element composition, and gas sensing performance of as-synthesized product. The hierarchical tin oxide nanoflowers exhibit sensitivity to 100 ppm methanol and the response is 58, which is ascribed to the hierarchical structure. The response and recovery time are 4 s and 8 s, respectively. Moreover, the as-prepared sensor has a low working temperature of 200 °C which is lower than that for other gas sensors of such type has been reported elsewhere. The excellent sensitivity of the sensor is caused by its complex phase mixture of SnO, SnO2, Sn2O3, and Sn6O4 revealed by XRD analysis. The proposed hierarchical tin oxide nanoflowers gas sensing material is promising for development of methanol gas sensor. The as-obtained hierarchical tin oxide nanoflower (HTONF) gas sensor shows excellent gas-sensing performance at low working temperature (200 °C) and high annealing temperature (400 °C).

Crystal recombination control by using Ce doped in mesoporous TiO2 for efficient perovskite solar cells

Efficient electron transport layers (ETLs) are the crucial issue for electron transport and hole blocking in organic-inorganic hybrid perovskite solar cells (PSCs). To date, most of the reported effective ETLs have comprised TiO2, which exhibits limited electron mobility and numerous defect states and restricts the enhancement of the performance of PSCs. Hence, the investigation of effective tactics for improving the electronic properties of TiO2 is critical for the fabrication of high-efficiency devices. In this study, a cerium doping method was adopted in mesoporous TiO2, which was prepared via a traditional one-step hydrothermal process, to improve its electron transport properties by recombining nanocrystals and optimizing the negative flat band potential of TiO2. Continuous, aligned and regulated recombined crystals of mesoporous TiO2 were obtained with optimized pathways of electron transport from the ETL to the FTO layer. Moreover, a small amount of Ti4+ ions was replaced by Ce4+ ions in the TiO2 lattice, which led to deformation of the TiO2 lattice and influenced the growth process of TiO2 grains. With an optimized mole proportion of Ce element in the TiO2 precursor, the power conversion efficiency (PCE) of perovskite solar cells was typically boosted to 17.75% in comparison with 15.92% in the case of undoped TiO2.

Low-temperature electrospray-processed SnO2 nanosheets as an electron transporting layer for stable and high-efficiency perovskite solar cells

Semiconducting metal oxide electron transporting layers (ETLs) with distinct morphologies have the ability to produce the less-hysteric and high efficiency perovskite solar cells (PSCs). Here, for the first time we introduce a viable electrospraying route for one-step deposition of highly mesoporous SnO₂ nanosheets, as the ETLs in PSCs with reduces hysteresis, high charge collection efficiency and improved ambient stability. Furthermore, optimization of the interfacial properties between the SnO₂ nanosheets and the perovskite absorber layer by the employment of a C60 interlayer consequences in decreasing the charge recombination, better energy level alignment, and significantly improved power conversion efficiency (PCE). Consequently, the efficient PSCs based on C60-modified SnO₂ nanosheets ETLs have almost hysteresis-free behavior, with a best PCE of 20.2% thanks to the highly porous nature of nanosheets and better perovskite infiltration. This study reveals that hierarchical SnO₂ is a possible ETL for producing low-cost and efficient PSCs with long-term stability.