Toward Large-Area and Fully Solution-Sheared Perovskite Solar Cells

Modular slot-die coater for in situ grazing-incidence x-ray scattering experiments on thin films

Multimodal in situ experiments during slot-die coating of thin films pioneer the way to kinetic studies on thin-film formation. They establish a powerful tool to understand and optimize the formation and properties of thin-film devices, e.g., solar cells, sensors, or LED films. Thin-film research benefits from time-resolved grazing-incidence wide- and small-angle x-ray scattering (GIWAXS/GISAXS) with a sub-second resolution to reveal the evolution of crystal structure, texture, and morphology during the deposition process. Simultaneously investigating optical properties by in situ photoluminescence measurements complements in-depth kinetic studies focusing on a comprehensive understanding of the triangular interdependency of processing, structure, and function for a roll-to-roll compatible, scalable thin-film deposition process. Here, we introduce a modular slot-die coater specially designed for in situ GIWAXS/GISAXS measurements and applicable to various ink systems. With a design for quick assembly, the slot-die coater permits the reproducible and comparable fabrication of thin films in the lab and at the synchrotron using the very same hardware components, as demonstrated in this work by experiments performed at Deutsches Elektronen-Synchrotron (DESY). Simultaneous to GIWAXS/GISAXS, photoluminescence measurements probe optoelectronic properties in situ during thin-film formation. An environmental chamber allows to control the atmosphere inside the coater. Modular construction and lightweight design make the coater mobile, easy to transport, quickly extendable, and adaptable to new beamline environments.

Eco-Friendly Solvent Engineered CsPbI2.77 Br0.23 Ink for Large-Area and Scalable High Performance Perovskite Solar Cells

The performance of large-area perovskite solar cells (PSCs) has been assessed for typical compositions, such as methylammonium lead iodide (MAPbI3 ), using a blade coater, slot-die coater, solution shearing, ink-jet printing, and thermal evaporation. However, the fabrication of large-area all-inorganic perovskite films is not well developed. This study develops, for the first time, an eco-friendly solvent engineered all-inorganic perovskite ink of dimethyl sulfoxide (DMSO) as a main solvent with the addition of acetonitrile (ACN), 2-methoxyethanol (2-ME), or a mixture of ACN and 2-ME to fabricate large-area CsPbI2.77 Br0.23 films with slot-die coater at low temperatures (40-50 °C). The perovskite phase, morphology, defect density, and optoelectrical properties of prepared with different solvent ratios are thoroughly examined and they are correlated with their respective colloidal size distribution and solar cell performance. The optimized slot-die-coated CsPbI2.77 Br0.23 perovskite film, which is prepared from the eco-friendly binary solvents dimethyl sulfoxide:acetonitrile (0.8:0.2 v/v), demonstrates an impressive power conversion efficiency (PCE) of 19.05%. Moreover, the device maintains ≈91% of its original PCE after 1 month at 20% relative humidity in the dark. It is believed that this study will accelerate the reliable manufacturing of perovskite devices.

Promoting Large-Area Slot-Die-Coated Perovskite Solar Cell Performance and Reproducibility by Acid-Based Sulfono-γ-AApeptide

Homogeneous and pinhole-free large-area perovskite films are required to realize the commercialization of perovskite modules and panels. Various large-area perovskite coatings were developed; however, at their film coating and drying stages, many defects were formed on the perovskite surface. Consequently, not only the devices lost substantial performance but also their long-term stability deteriorated. Here, we fabricated a compact and uniform large-area MAPbI₃-perovskite film by a slot-die coater at room temperature (T) and at high relative humidity (RH) up to 40%. The control slot-die-coated perovskite solar cell (PSC) produced 1.082 V open-circuit voltage (V_oc), 24.09 mA cm^-2 short current density (J_sc), 71.13% fill factor (FF), and a maximum power conversion efficiency (PCE) of 18.54%. We systematically employed a multi-functional artificial amino acid (F-LYS-S) to modify the perovskite defects. Such amino acids are more inclined to bind and adhere to the perovskite defects. The amino, carbonyl, and carboxy functional groups of F-LYS-S interacted with MAPbI₃ through Lewis acid-base interaction and modified iodine vacancies significantly. Fourier transform infrared spectroscopy revealed that the C═O group of F-LYS-S interacted with the uncoordinated Pb²⁺ ions, and X-ray photoelectron spectroscopy revealed that the lone pair of -NH₂ coordinated with the uncoordinated Pb²⁺ and consequently modified the I^- vacancies remarkably. As a result, the F-LYS-S-modified device demonstrated more than three-fold charge recombination resistance, which is one of the primary requirements to fabricate high-performance PSCs. Therefore, the device fabricated employing F-LYS-S demonstrated remarkable PCE of 21.08% with superior photovoltaic parameters of 1.104 V V_oc, 24.80 mA cm^-2 J_sc, and 77.00%. FF. Concurrently, the long-term stability of the PSCs was improved by the F-LYS-S post-treatment, where the modified device retained ca. 89.6% of its initial efficiency after storing for 720 h in air (T ∼ 27 °C and RH ∼ 50-60%).

Recent Developments in Upscalable Printing Techniques for Perovskite Solar Cells

Just over a decade, perovskite solar cells (PSCs) have been emerged as a next-generation photovoltaic technology due to their skyrocketing power conversion efficiency (PCE), low cost, and easy manufacturing techniques compared to Si solar cells. Several methods and procedures have been developed to fabricate high-quality perovskite films to improve the scalability and commercialize PSCs. Recently, several printing technologies such as blade-coating, slot-die coating, spray coating, flexographic printing, gravure printing, screen printing, and inkjet printing have been found to be very effective in controlling film formation and improving the PCE of over 21%. This review summarizes the intensive research efforts given for these printing techniques to scale up the perovskite films as well as the hole transport layer (HTL), the electron transport layer (ETL), and electrodes for PSCs. In the end, this review presents a description of the future research scope to overcome the challenges being faced in the printing techniques for the commercialization of PSCs.