Development of High Efficiency, Spray-Coated Perovskite Solar Cells and Modules Using Additive-Engineered Porous PbI2 Films.

The development of anti-solvent free, scalable, and printable perovskite film is crucial to realizing the low-cost roll-to-roll development of perovskite solar cells (PSCs). Herein, large-area perovskite film fabrication is explored using a spray-assisted sequential deposition technique. How propylene carbonate (PC) solvent additive affects the transformation of lead halide (PbI2 ) into perovskite at room temperature is investigated. The result shows that PC-modified perovskite films exhibit a uniform, pinhole-free morphology with oriented grains compared with pristine perovskite films. The PC-modified perovskite film also has a prolonged fluorescence lifetime that indicates lower carrier recombination. The champion PSC devices based on PC-modified perovskite film realize a power conversion efficiency (PCE) of 20.5% and 19.3% at an active area (A) of 0.09 cm2 and 1 cm2 , respectively. The fabricated PSCs are stable and demonstrate ≥85% PCE retention following 60 days of exposure to ambient conditions. Furthermore, perovskite solar modules (A ≈ 13 cm2 ) that yield a PCE of 15.8% are fabricated. These results are among the best reported for the state-of-art spray-coated PSCs. Spray deposition coupled with a PC additive is highly promising for economical and high-output preparation of PSCs.

Selective aerobic coupling of amines to imines using solar spectrum-responsive flower-like Nen-graphene quantum dots (GQDs) decorated with 2, 4-dinitrophenylhydrazine (PH) as a photocatalyst.

Indeed, the development of ecologically benign molecular fabrication methods for highly efficient graphene quantum dots-based photocatalysts is of great significant. Graphene quantum dots-based photocatalysts have promising applications in various field, including environmental remediation, energy conversion, and splitting of water. However, ensuring resource reusability and minimizing the environmental impact are crucial considerations in the development. From this perspective, attention has also been paid to the creation of easy to make solar light harvesting graphene quantum dots-based photocatalysts for synthesising pharmaceuticals and functional imines compounds. Imines are excellent significant building blocks in pharmaceutical chemistry and excellent examples of these valuable compounds' synthetic intermediates, and the environmentally friendly oxidative synthesis of imines from amines. Therefore, herein, we designed a facile and efficient condensation route to synthesize the Nen-GQDs@PH photocatalyst. This route involves coupling of 2,4-dinitrophenylhydrazine (PH) with nitrogen-enriched graphene quantum dots (Nen-GQDs). The Nen-GQDs@PH as photocatalyst functions in a highly selective and efficient manner, leading to high amines conversion efficiency to imines (95%). Our results highlight a novel and environmentally safe approach for generating highly selective imines from various types of amines, setting a new benchmark in the current research field.

Room-Temperature Spray Deposition of Large-Area SnO2 Electron Transport Layer for High Performance, Stable FAPbI3 -Based Perovskite Solar Cells.

The performance and scalability of perovskite solar cells (PSCs) is highly dependent on the morphology and charge selectivity of the electron transport layer (ETL). This work demonstrates a high-speed (1800 mm min-1 ), room-temperature (25 °C-30 °C) deposition of large-area (62.5 cm2 ) tin oxide films using a multi-pass spray deposition technique. The spray-deposited SnO2 (spray-SnO2 ) films exhibit a controllable thickness, a unique granulate morphology and high transmittance (≈85% at 550 nm). The performance of the PSC based on spray-SnO2 ETL and formamidinium lead iodide (FAPbI3 )-based perovskite is highly consistent and reproducible, achieving a maximum efficiency of ≈20.1% at an active area (A) of 0.096 cm2 . Characterization results reveal that the efficiency improvement originates from the granular morphology of spray-SnO2 and high conversion rate of PbI2 in the perovskite. More importantly, spray-SnO2 films are highly scalable and able to reduce the efficiency roll-off that comes with the increase in contact-area between SnO2 and perovskite film. Based on the spray-SnO2 ETL, large-area PSC (A = 1.0 cm2 ) achieves an efficiency of ≈18.9%. Furthermore, spray-SnO2 ETL based PSCs also exhibit higher storage stability compared to the spin-SnO2 based PSCs.

High-performance, color-tunable fiber shaped organic light-emitting diodes.

In recent years, extensive research has been undertaken to develop fiber-shaped optoelectronic devices, because they are aesthetically pleasing, light in weight, and exhibit superior light emitting properties when compared with conventional planar analogues. In this work, we have successfully developed hollow-fiber shaped organic light emitting diodes (HF-OLED) with an exceptionally high luminance and facile color tunability. The HF-OLED device was fabricated by hierarchically depositing amorphous indium-doped tin oxide electrode on a hollow-fiber, followed by the sequential deposition of light-emitting organic layers and Al cathode. The external quantum efficiency of the HF-OLED is more than ∼2.0 times higher than that of a planar-OLED. The experimental results are in good agreement with the output of optical simulations, revealing that the use of a hollow-fiber has contributed to a ∼2.3 times improvement in light extraction efficiency. Furthermore, the color emission of a single HF-OLED device could be easily tuned from a green to yellowish-green wavelength after the injection of a super-yellow solution. The novel color tunable nature of the HF-OLED further broadens its application in the field of modern lighting and display technology.

Fabrication of perovskite films using an electrostatic assisted spray technique: the effect of the electric field on morphology, crystallinity and solar cell performance.

An electric field assisted spray deposition method is employed for improving the perovskite film morphology, crystallinity, and surface coverage, and for further fabricating an efficient solar cell. By applying different voltages ranging from 0.5 to 2.0 kV during spray deposition, we observed a large variation in the film morphology and surface coverage compared to those fabricated without an electric field, which is due to improved atomization from the Coulomb fission process. The optimized applied voltage of 1.5 kV during spraying led to completion of the reaction between CH3NH3I and PbI2 on a hot substrate for pure phase CH3NH3PbI3 thin film formation with improved grain growth and surface coverage. The cells fabricated using perovskite films showed clear applied voltage dependence in the energy conversion process and alleviation in J-V hysteresis; with 1.5 kV applied voltage the average cell efficiency of 8.9% was obtained compared to films fabricated without applying voltage providing only 6.5%. The best efficiencies are 10.9% and 7.37% for applied voltages of 1.5 kV and 0 kV, respectively. The enhancement in efficiency with applied voltage is due to the formation of more uniform and dense films with large perovskite crystals, which resulted in efficient electron transportation (enhanced photocurrent and modified series and shunt resistances) by minimizing the charge carrier recombination at grain boundaries (resulting in enhanced open circuit voltage). With further optimization of the perovskite film thickness by adjusting the CH3NH3I spray volume, the average cell efficiency of ∼11.0% was obtained.

Fabrication of polymer/cadmium sulfide hybrid solar cells [P3HT:CdS and PCPDTBT:CdS] by spray deposition.

This paper investigates fabrication of surfactant free CdS nanoparticles (NPs) and application in the fabrication of P3HT:CdS and PCPDTBT:CdS bulk-heterojunction hybrid solar cells using high-throughput, large-area, low cost spray deposition technique. Both the hybrid active layers and hole transport layers are deposited by spray technique. The CdS/Poly(3-hexylthiophene-2,5-diyl) (P3HT) and CdS/Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) hybrid devices are fabricated by spray deposition process at optimized conditions (i.e. film thickness, spray solution volume, distance between sample and spray nozzle, substrate temperature, etc.). The power conversion efficiency of η=0.6% and 1.02% is obtained for P3HT:CdS and PCPDTBT:CdS hybrid devices, respectively. Spray coating holds significant promise as a technique capable of fabricating large-area, high performance hybrid solar cells.