Perovskite solar cells (PSCs) have developed rapidly over the past few years, and the power conversion efficiency of PSCs has exceeded 20%. Such high performance can be attributed to the unique properties of perovskite materials, such as high absorption over the visible range and long diffusion length. Due to the different diffusion lengths of holes and electrons, electron transporting materials (ETMs) used in PSCs play a critical role in PSCs performance. As an alternative to TiO ETM, ZnO materials have similar physical properties to TiO but with much higher electron mobility. In addition, there are many simple and facile methods to fabricate ZnO nanomaterials with low cost and energy consumption. This review focuses on recent developments in the use of ZnO ETM for PSCs. The fabrication methods of ZnO materials are briefly introduced. The influence of different ZnO ETMs on performance of PSCs is then reviewed. The limitations of ZnO ETM-based PSCs and some solutions to these challenges are also discussed. The review provides a systematic and comprehensive understanding of the influence of different ZnO ETMs on PSCs performance and potentially motivates further development of PSCs by extending the knowledge of ZnO-based PSCs to TiO -based PSCs.

Electronics on flexible and transparent substrates have received much interest due to their new functionalities and high-speed roll-toroll manufacturing processes. The properties of substrates are crucial, including flexibility, surface roughness, optical transmittance, mechanical strength, maximum processing temperature, etc.Although plastic substrates have been used widely in flexible macroelectronics, there is still a need for next-generation sustainable, high-performance substrates which are thermally stable with tunable optical properties and a higher handling temperature. In this communication, we focus on cellulose-based transparent, biodegradable substrates incorporating either nanopaper or a regenerated cellulose film (RCF). We found that both their optical and mechanical properties are dramatically different due to the difference of their building blocks. Highly flexible organic-light-emitting diodes (OLEDs) are also demonstrated on the biodegradable substrates, paving the way for next-generation green and flexible electronics.

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With the rapid development of organic-inorganic lead halide perovskite photovoltaics, increasingly more attentions are paid to explore the growth mechanism and precisely control the quality of perovskite films. In this study, we propose a "stitching effect" to fabricate high quality perovskite films by using chlorobenzene (CB) as an anti-solvent and isopropyl alcohol (IPA) as an additive into this anti-solvent. Because of the existence of IPA, CB can be efficiently released from the gaps of perovskite precursors and the perovskite film formation can be slightly modified in a controlled manner. More homogeneous surface morphology and larger grain size of perovskite films were achieved via this process. The reduced grain boundaries ensure low surface defect density and good carrier transport in the perovskite layer. Meanwhile, we also performed the Fourier transform infrared (FTIR) spectroscopy to investigate the film growth mechanism of unannealed and annealed perovskite films. Solar cells fabricated by using the "stitching effect" exhibited a best efficiency of 19.2%. Our results show that solvent and solvent additives dramatically influenced the formation and crystallization processes for perovskite materials due to their different coordination and extraction capabilities. This method presents a new path towards controlling the growth and morphology of perovskite films.

To date, various stretchable conductors have been fabricated, but simultaneous realization of the transparency, high stretchability, electrical conductivity, self-healing capability, and sensing property through a simple, fast, cost-efficient approach is still challenging. Here, α-lipoic acid (LA), a naturally small biological molecule found in humans and animals, is used to fabricate transparent (>85%), electrical conductivity, highly stretchable (strain up to 1100%), and rehealable (mechanical healing efficiency of 86%, electrical healing efficiency of 96%) ionic conductor by solvent-free one-step polymerization. Furthermore, the ionic conductors with appealing sensitivity can be served as strain sensors to detect and distinguish various human activities. Notably, this ionic conductor can be fully recycled and reprocessed into new ionic conductors or adhesives by a direct heating process, which offers a promising prospect in great reduction of electronic wastes that have brought acute environmental pollution. In consideration of the extremely facile preparation process, biological available materials, satisfactory functionalities, and full recyclability, the emergence of LA-based ionic conductors is believed to open up a new avenue for developing sustainable and wearable electronic devices in the future.features. [1][2][3][4] These conductors provide huge opportunities for promising applications of artificial muscles, skin sensors, biological actuators, stretchable displays, electronic eye cameras, intelligent robot arms, and others. [5][6][7][8][9][10][11] It was well known that the conventional electronic conductors are normally prepared from waferbased materials, which possess several drawbacks including fragility, rigidity, and low conductivity under large-scale deformations. [12] They cannot satisfy the demands of high stretchability, flexibility, durability, and stability. To achieve these criteria, strain engineering and nanocomposites are the two most adoptable strategies to fabricate stretchable conductors. In the first strategy, nonstretchable inorganic materials, such as silicon and metals, are geometrically patterned into buckled, serpentine structures on elastomeric substrates that renders the conductors excellent sensitivity and larger workable range of strain. [10,13,14] Nonetheless, most resultant conductors still show narrow range of strain from 20% to 70%, [15] and presents out-of-plane patterns that is difficult to encapsulate. Meanwhile, this strategy usually involves expensive and very complicated techniques, which greatly limits the further development of these conductors. Integrating conductive fillers into polymer matrix to produce nanocomposites used as stretchable conductors is the second strategy. [16] So far, various nanomaterials, such as carbon nanotubes, [17][18][19][20] carbon black, [21] graphene-based materials, [22,23] metal nanowires, and nanoparticles, [24,25] have been used as conductive fillers because of their unique mechanical and electrical properties. Although the robu...

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Despite dramatically improved efficiency of inorganic-organic metal hybrid perovskite solar cells (PSCs), electron transport is still a challenging issue. In this paper, we report the use of ZnO nanorods prepared by hydrothermal self-assembly as the electron transport layer in perovskite solar cells. The efficiency of perovskite solar cells is dramatically enhanced by passivating the interface defects via atomic layer deposition of Al2O3 monolayers on ZnO nanorods. By employing Al2O3 monolayers, the power conversion efficiency (PCE) of CH3NH3PbI3 (MAPbI3) PSCs is typically boosted from 10.33% to 15.06% on average, with the highest efficiency of 16.08%. We suggest that passivation of defects using atomic layer deposition of monolayers might provide a new pathway for improving all types of PSCs. 1 Instruction Although sunlight is a clean, cheap, abundant, and renewable energy source, it is poorly utilized. The growing demand for cheap and renewable energy sources has led to substantial research effort to invent low-cost and highly-efficient photovoltaic materials and devices. third generation solar cells, halide perovskite solar cells (PSCs) have a great

Ionic conductors are normally prepared from water-based materials in the solid form and feature a combination of intrinsic transparency and stretchability. The sensitivity toward humidity inevitably leads to dehydration or deliquescence issues, which will limit the long-term use of ionic conductors. Here, a novel ionic conductor based on natural bacterial cellulose (BC) and polymerizable deep eutectic solvents (PDESs) is developed for addressing the abovementioned drawbacks. The superstrong three-dimensional nanofiber network and strong interfacial interaction endow the BC−PDES ionic conductor with significantly enhanced mechanical properties (tensile strength of 8 × 10 5 Pa and compressive strength of 6.68 × 10 6 Pa). Furthermore, compared to deliquescent PDESs, BC−PDES composites showed obvious mechanical stability, which maintain good mechanical properties even when exposed to high humidity for 120 days. These materials were demonstrated to possess multiple sensitivity to external stimulus, such as strain, pressure, bend, and temperature. Thus, they can easily serve as supersensitive sensors to recognize physical activity of humans such as limb movements, throat vibrations, and handwriting. Moreover, the BC−PDES ionic conductors can be used in flexible, patterned electroluminescent devices. This work provides an efficient strategy for making cellulose-based sustainable and functional ionic conductors which have broad application in artificial flexible electronics and other products.