Lights and Shadows of DMSO as Solvent for Tin Halide Perovskites

In 2020 dimethyl sulfoxide DMSO , the ever present solvent for tin halide perovskites, was identified as an oxidant for SnII. Nonetheless, alternatives are lacking and few efforts have been devoted to replacing it. To understand this trend it is indispensable to learn the importance of DMSO on the development of tin halide perovskites. Its unique properties have allowed processing compact thin films to be integrated into tin perovskite solar cells. Creative approaches for controlling the perovskite crystallization or increasing its stability to oxidation have been developed relying on DMSO based inks. However, increasingly sophisticated strategies appear to lead the field to a plateau of power conversion efficiency in the range of 10 15 amp; 8201; . And, while DMSO based formulations have performed in encouraging means so far, we should also start considering their potential limitations. In this concept article, we discuss the benefits and limitations of DMSO based tin perovskite processin

Pyridine Controlled Tin Perovskite Crystallization

Controlling the crystallization of perovskite in a thin film is essential in making solar cells. Processing tin based perovskite films from solution is challenging because of the uncontrollable faster crystallization of tin than the most used lead perovskite. The best performing devices are prepared by depositing perovskite from dimethyl sulfoxide because it slows down the assembly of the tin iodine network that forms perovskite. However, while dimethyl sulfoxide seems the best solution to control the crystallization, it oxidizes tin during processing. This work demonstrates that 4 tert butyl pyridine can replace dimethyl sulfoxide to control the crystallization without oxidizing tin. We show that tin perovskite films deposited from pyridine have a 1 order of magnitude lower defect density, which promotes charge mobility and photovoltaic performanc

An open-access database and analysis tool for perovskite solar cells based on the FAIR data principles

Large datasets are now ubiquitous as technology enables higher-throughput experiments, but rarely can a research field truly benefit from the research data generated due to inconsistent formatting, undocumented storage or improper dissemination. Here we extract all the meaningful device data from peer-reviewed papers on metal-halide perovskite solar cells published so far and make them available in a database. We collect data from over 42, 400 photovoltaic devices with up to 100 parameters per device. We then develop open-source and accessible procedures to analyse the data, providing examples of insights that can be gleaned from the analysis of a large dataset. The database, graphics and analysis tools are made available to the community and will continue to evolve as an open-source initiative. This approach of extensively capturing the progress of an entire field, including sorting, interactive exploration and graphical representation of the data, will be applicable to many fields in materials science, engineering and biosciences. © 2021, The Author(s)

Small angle scattering to reveal the colloidal nature of halide perovskite precursor solutions

Halide perovskites are crystalline semiconductors gaining increasing attention as low cost, high performance materials for optoelectronics. Their processing from solution at low temperatures is compatible with rapid manufacturing of thin film devices, including solar cells and light emitting diodes. Therefore, understanding the coordination chemistry in metal halide perovskite precursor solutions would allow controlling the crystallization of thin films, their material properties and device performance. Here, we present a direct nanostructural technique to characterize the colloidal structure of perovskites in precursor solutions. Small angle scattering is particularly adept for measuring nanoparticles in solution. Applying this technique to perovskite precursor solutions, we can study their colloidal properties. We show that not only do the colloids themselves matter, but also we can reveal their strong interactions in the early stages of crystallization. In particular, we focus on the prearrangement of particles into cluster like formations. As an example, we present the concentration dependence, which is additionally supported using 207Pb NM

Role of Terminal Group Position in Triphenylamine Based Self Assembled Hole Selective Molecules in Perovskite Solar Cells

The application of self assembled molecules SAMs as a charge selective layer in perovskite solar cells has gained tremendous attention. As a result, highly efficient and stable devices have been released with stand alone SAMs binding ITO substrates. However, further structural understanding of the effect of SAM in perovskite solar cells PSCs is required. Herein, three triphenylamine based molecules with differently positioned methoxy substituents have been synthesized that can self assemble onto the metal oxide layers that selectively extract holes. They have been effectively employed in p i n PSCs with a power conversion efficiency of up to 20 . We found that the perovskite deposited onto SAMs made by para and ortho substituted hole selective contacts provides large grain thin film formation increasing the power conversion efficiencies. Density functional theory predicts that para and ortho substituted position SAMs might form a well ordered structure by improving the SAM s arrangement and in consequence enhancing its stability on the metal oxide surface. We believe this result will be a benchmark for the design of further SAM

20.8 Slot Die Coated MAPbI 3 Perovskite Solar Cells by Optimal DMSO Content and Age of 2 ME Based Precursor Inks

Solar cells incorporating metal-halide perovskite (MHP) semiconductors are continuing to break efficiency records for solution-processed solar cell devices. Scaling MHP-based devices to larger area prototypes requires the development and optimization of scalable process technology and ink formulations that enable reproducible coating results. It is demonstrated that the power conversion efficiency (PCE) of small-area methylammonium lead iodide (MAPbI3) devices, slot-die coated from a 2-methoxy-ethanol (2-ME) based ink with dimethyl-sulfoxide (DMSO) used as an additive depends on the amount of DMSO and age of the ink formulation. When adding 12 mol% of DMSO, small-area devices of high performance (20.8%) are achieved. The effect of DMSO content and age on the thin film morphology and device performance through in situ X-ray diffraction and small-angle X-ray scattering experiments is rationalized. Adding a limited amount of DMSO prevents the formation of a crystalline intermediate phase related to MAPbI3 and 2-ME (MAPbI3-2-ME) and induces the formation of the MAPbI3 perovskite phase. Higher DMSO content leads to the precipitation of the (DMSO)2MA2Pb3I8 intermediate phase that negatively affects the thin-film morphology. These results demonstrate that rational insights into the ink composition and process control are critical to enable reproducible large-scale manufacturing of MHP-based devices for commercial applications

Role of the Alkali Metal Cation in the Early Stages of Crystallization of Halide Perovskites

ABX3 metal halide perovskites revolutionized the research and development of new optoelectronics, including solar cells and light emitting diodes. Processing polycrystalline thin films from precursor solutions is one of the core advantages of these materials since it enables versatile and cost effective manufacturing. The perovskite film morphology, that is, continuous substrate coverage and low surface roughness, is of paramount importance for highly efficient solar cells and optoelectronic devices in general. Controlling the chemistry of precursor solutions is one of the most effective strategies to manage the perovskite film morphology. Herein, we show the fundamental influence of the A site cation composition on the perovskite precursor arrangement and the consequent film formation. Extended X ray absorption fine structure spectroscopy and small angle X ray scattering give unprecedented insights into the complex structural chemistry of the perovskite precursors and, in particular, their epulsive interactions as a crucial parameter for colloidal stability. Combining these techniques with in situ grazing incidence wide angle X ray scattering during thin film formation allows us to identify the mechanism for using alkali metals as a decisive criterion to control the colloidal stability of the perovskite precursor and thus the thin film morphology. We illustrate the fundamental principle behind the systematic use of alkali metals regardless of whether they are incorporated in the lattice or not. Hence, this work provides tools to selectively control the morphology and crystal growth in present and future system