Predicting Low Toxicity and Scalable Solvent Systems for High Speed Roll-to-Roll Perovskite Manufacturing

Abstract

This manuscript introduces solvent toxicity in solar perovskite ink chemistries as a major technoeconomic limitation for the growth of the technology. More specifically, the capital and operational cost of handling such toxic chemicals to maintain a safe working environment can lead to significant added costs. As all record power conversion efficiency devices to date have been solution processed, this represents a major challenge for the perovskite optoelectronic field and of printed electronics as a whole. Knowing this limitation, we propose that solvent selections for ink chemistries should be more quantitative and focus on lowering toxicity. To this end, we show that a Hansen solubility model is effective in predicting ink systems using lower toxicity solvents. We also show that inks formed from this method are applicable for high-speed slot-die coating, limiting the need for long anneal times. These methods and results demonstrate a useful framework for quantitatively engineering solvent systems with reduced toxicity while simultaneously maintaining and surpassing performance. It therefore provides a pathway and major step forward towards the commercialization of solution coated perovskite technologies.

Solvent–antisolvent interactions in metal halide perovskites

“…Further, also acetonitrile (ACN), N-methyl-2-pyrrolidone (NMP), g-butyrolactone (GBL), tetrahydrofuran (THF) and dimethylacetamide (DMAc) are among the most commonly investigated solvents. [53][54][55] Motivated by the search for a ''green'' solvent, even water has been successfully tested on certain perovskite compositions and device structures. 56 The range of antisolvents employed by the perovskite research community is significantly broader, including polar, protic, aprotic and non-polar solvents with high and low dipole moments and boiling points.…”

“…72,74 A more sophisticated model to describe these interactions is given by the Hansen Solubility Parameters. Furthermore, these parameters are easily applicable to solvents, antisolvents and solvent-or antisolvent mixtures, 54 as well as precursors 75,76 and can be plotted in Hansen parameter space, giving a good visual and numerical guideline of the interactions between the component materials included in the perovskite formation. While some studies on perovskite solar cells have considered HSPs, these so far focused solely on solvent-perovskite interactions and thus, an overview of the positions in HSP space of commonly used solvents and antisolvents combinations which would be useful for the field has yet to be presented.…”

“…Some reports have proven the potential of using HSP theory to lower the toxicity of MHP films, not only by substituting hazardous chemicals by ones with low toxicity, but also by predicting the compatibility of low toxicity solvents with salt precursors towards a greener fabrication of metal halide perovskite-based PV devices. 54,75,96 In this context the Hansen solubility model can be highly effective in finding suitable, non-hazardous solvents to solubilize lead salts for the fabrication of lead halide perovskite films by providing insight into the interaction between the salts and the solvents employed, as suggested by Dooling et al 96 The substitution of hazardous solvents for greener ones would aid avoiding unintended consequences from adopting alternative solvent systems Visually inspecting the plotted Hansen space in Fig. 5(b), candidates to substitute DMF can be elucidated, such as DMAc.…”

“…Some reports have proven the potential of using HSP theory to lower the toxicity of MHP films, not only by substituting hazardous chemicals by ones with low toxicity, but also by predicting the compatibility of low toxicity solvents with salt precursors towards a greener fabrication of metal halide perovskite-based PV devices. 54,75,96 …”

One-Step Blade Coating of Inverted Double-Cation Perovskite Solar Cells from a Green Precursor Solvent

“…33,34 Multi-cation perovskite precursor solutions usually utilize solvent mixtures of toxic N,N-dimethylformamide (DMF) as the main component and only little amount of cosolvents 29,30,39 also in order to guarantee the solubility of all precursor materials including cesium iodide (CsI). 40,41 However, for upscaling to mass production and commercialization, appropriate handling of the toxic main constituent of the solvent system must be already considered during the initial development phase, 42,43 which is the focus of this work.…”