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Anti‐solvent assisted crystallization (ASAC) is currently one of the most widely used methods to obtain perovskite films with great quality due to its advantage of low cost and easy operation. The commonly used anti‐solvents, toluene, and chlorobenzene (CB), are well recognized to be contaminants in drinking water and exhibit high toxicity levels. It is desirable to develop environmentally benign solvents for the fabrication of perovskite solar cells by ASAC method. As a green solvent, methoxybenzene (PhOMe) has the advantages of low toxicity, moderate saturated vapor pressure, and similar solvent features with toluene and CB. Here, we report highly efficient planar perovskite solar cells (PSCs) prepared by ASAC method using PhOMe green anti‐solvent, achieving a power conversion efficiency (PCE) of 19.42%, which is better than CB processed PSCs (19.09%). Compared to CB processed perovskite films, perovskites produced by PhOMe exhibit smoother surfaces, larger grains, and lower carrier recombination rates, while the crystallization and absorption features remain basically unchanged. These results demonstrate that PhOMe is an excellent anti‐solvent alternative for high‐quality perovskites and thus provide new opportunities for environmental‐friendly manufacturing of PSCs and other optoelectronic devices.

It is essential to minimize the interfacial trap states and improve the carrier collection for high efficiency perovskite solar cells (PSCs). Herein, we present a facile method to construct a p-type graded heterojunction (GHJ) in normal PSCs by deploying a gradient distribution of hole-transporting materials (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], PTAA, in this case) in the shallow perovskite layer. The formation of the GHJ structure facilitates charge transfer and collection, and passivates interfacial trap states, thus delivering a power conversion efficiency (PCE) of 20.05 % along with steady output efficiency of 19.3 %, which is among the highest efficiencies for cesium formamidinium (Cs-FA) lead halide PSCs. Moreover, the unencapsulated devices based on these (Cs-FA) lead halide perovskites show excellent long-term stability; more than 95 % of their initial PCE can be retained after 1440 h storage under ambient conditions. This study may provide an effective strategy to fabricate high-efficiency PSCs with great stability.

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A kind of one step and in situ etching method is developed to fabricate a highly optically transparent and flexible self-cleaning superhydrophobic film (SSF). This SSF exhibits a very rough surface morphology with hierarchical structure, which makes it have a contact angle of 154.6° and a sliding angle of smaller than 1°. And the SSF can also be self-cleaned in the wind. The SSF hierarchical structure scatters the incident light, but it almost doesn't attenuate the light. So the SSF has antireflection properties and a high light transmittance of 94%. The excellent self-cleaning property, high light transmittance and antireflection property mean that the SSF greatly enhances the performance of solar cells in practical working conditions. The solar cell's efficiency maintains at 95.8% of its initial value after covering with the SSF, which is about 1.7 times higher than that of the solar cell covered with dust, as in practical conditions.

TiO2 is the most widely used electron transport layer (ETL) in high performance perovskite solar cells (PSCs). However, TiO2 often induces a rapid decay in performance under ultraviolet (UV) light illuminations. So, high performance ETL is urgently needed for PSCs. Here, a new kind of Nb2O5 nanoparticles ETL was developed for fabricating efficient planar PSCs with excellent UV stability. The matched band alignment between perovskites and Nb2O5 promotes electron injection at the ETL/perovskite interface, and decreases the energy barrier for electron injection. Decreased energy loss during electron transfer from perovskite to Nb2O5 and lower recombination rates in the devices contribute to the improved open-circuit voltage (V oc) of PSCs on Nb2O5 compared to devices on TiO2. Power conversion efficiency (PCE) surpassing 20% with a high V oc of 1.19 V was demonstrated for planar PSCs with Nb2O5 ETL. The unencapsulated devices based on Nb2O5 retained 93% of their initial short-circuit current density (J sc) after 10 h exposure to concentrated 365 nm UV light (46 mW/cm2), versus 40% for devices based on TiO2, which was attributed to the excellent chemical stability nature of Nb2O5 under UV light.

Highly crystalline Nb:TiO2 nanospindles have been successfully exploited as efficient ETMs in planar perovskite solar cells, achieving a power conversion efficiency of 20.8%, superior to that of the undoped one (19.1%).

Flexible perovskite solar cells (PSCs) possess compatible features with low-cost, high throughput production approaches, showing great potentials in wearable, portable, flyable, and deployable applications. However, flexible PSCs with superior efficiency are commonly fabricated with an anti-solvent assisted crystallization (ASAC) method, which uses highly toxic solvents as the processed solvents. In this work, we use environmentally benign anti-solvents for the fabrication of flexible PSCs. Benefiting from the low-temperature solution processability of a high quality SnO2 electron transport layer (ETL) with superior electron extraction and transfer features, flexible PSCs show an impressive PCE over 17% under reverse scan. This, to the best of our knowledge, is among the highest performances for flexible PSCs and is the first report for flexible PSCs fabricated by green anti-solvent processed techniques. These results provide new opportunities for environmental-friendly manufacturing of high performance flexible PSCs.