Suppression of Coffee‐Ring Effect in Air‐Processed Inkjet‐Printed Perovskite Layer toward the Fabrication of Efficient Large‐Sized All‐Printed Photovoltaics: A Perovskite Precursor Ink Concentration Regulation Strategy

Abstract

Inkjet‐printing technology is anticipated to play a forefront role in the future prototyping of perovskite solar cells (PSCs) to enable their ultralow‐cost and scalable manufacturing. However, key inkjet challenges related to fluid dynamics should be first addressed to allow the fabrication of high‐quality printed materials and subsequently competitive photovoltaics to the established market. Herein, piezoelectric drop‐on‐demand inkjet‐printing is employed with the aim of developing high‐efficiency, stable, and reproducible large‐sized all‐printed perovskite modules under ambient atmospheric conditions. The focus of this work is put on the study of the influence of perovskite precursor ink concentration on the jet‐ability of the ink, on the wettability of the substrate by the ink, as well as on the characteristics of the inkjet‐printed perovskite layers and correspondingly of the PSCs. The results show that by employing a facile and universal perovskite precursor ink concentration regulation strategy, the coffee‐ring effect (recorded by in situ video microscopy) is greatly suppressed, leading to the fabrication of much better quality perovskite layers and correspondingly more efficient and stable photovoltaics. Finally, the development of all‐printed carbon‐based hole‐transport‐material‐free perovskite submodules is demonstrated, along with low upscaling efficiency losses (8.1%rel dec−1) and outstanding stability (<5% performance degradation after 1000 h of ageing).

Development of Greener and Stable Inkjet‐Printable Perovskite Precursor Inks for All‐Printed Annealing‐Free Perovskite Solar Mini‐Modules Manufacturing

“…Talking about the periodical morphological defects that appear in the perovskite films developed by the 1.8 m DMF-based ink, these arise from the coffee-ring effect and Marangoni convection evolved during the inkjet-printing procedure, as is also demonstrated in previous investigations. [13,31] According to these reports, the different evaporation rates of the solvent in a drop surface induce high capillary flows, while the surface tension gradient from the regions of high material concentration to the regions of low material concentration produces Marangoni convection, finally leading to the development of a zone of low material density (called "depletion zone"). Herein, the evolution of the coffee-ring effect for both cases of inks can be viewed in the drying drop experiments demonstrated in Video S1 (Supporting Information).…”

“…However, as indicated by comparing the crystallization kinetics of the two cases, the fluid dynamics are significantly more prominent for the wet film produced by the 1.8 m According to previous studies, this phenomenon is much more pronounced in the case of inks composed of low-concentration perovskite precursors. [13] On the other side, by the usage of GVLbased ink, a better wetting of the ETM by the ink is achieved, while the development of perovskite crystals is found to be totally uniform, favored under the tailored evaporation of the GVL solvent. At this point, it is noteworthy to mention that the vapor pressure of GVL solvent presents a low variation with temperature (ranging from 0.65 kPa at 25 °C to 3.5 kPa at 80 °C), unlike the commonly used solvents in PSCs development, such as DMF.…”

“…[10] Nevertheless, continuous efforts are also put toward the maturation of the inkjet-printing processing of PSCs, with the key inkjet challenges to be thoroughly considered in case studies devoted to provide sustainable solutions to the faced manufacturing issues, with one of the most critical ones being the coffee-ring effect. [12,13] To these challenges, several critical steps should be yet taken to proceed with a real high-quality and throughput industrial manufacturing of PSCs.…”

Rapid 2D Patterning of High‐Performance Perovskites Using Large Area Flexography

“…Nozzle-based methods such as inkjet printing have been applied for patterning of perovskite features down to 250 μm, [17,18] which can be an advantage in fabrication of perovskite photodetectors, [19] LEDs, [18] and solar cells. [20,21] However, this method has been applied at very low speeds (< 0.06 m min −1 ), requiring long processing times that are not ideal for high throughput or large area device fabrication. [18] Pushing the resolution of this technology causes drastic drops in throughput as finer features require smaller nozzles and require excessive amounts of time to raster patterns on the substrate, creating a significant tradeoff between speed and resolution (DPI) when Table 1.…”

High-Quality Patterning of CsPbBr3 Perovskite Films through Lamination-Assisted Femtosecond Laser Ablation toward Light-Emitting Diodes

“…On account of the remarkable optoelectronic properties of tunable emission wavelength, high color purity, and high optical absorption coefficient, metal halide perovskites have been regarded as promising candidates for diverse applications, such as photodetectors, lasers, photovoltaic devices, and light-emitting diodes (LEDs). − However, confronting the requirements of practical applications such as image sensors and displays, the realization of high-quality and high-precision patterned halide perovskite films is of central importance. − The conventional photolithography and inkjet printing are the most extensively employed and promising patterning technologies. − However, limited by the chemical instability of perovskite materials in various solvents, challenges still remain in ensuring the photophysical properties of the high-precision patterned perovskite films in the photolithography process. , In addition, the coffee ring effect and the subsequent solvent evaporation process in the process of inkjet printing could result in the non-uniformity of the patterned perovskite films, hindering further fabrication of perovskite-based optoelectronic devices. − In this regard, a high-precision and facile patterning technique for highly uniform and high-quality perovskite films without superfluous chemicals toward perovskite-based optoelectronic devices is highly desirable. , …”