Hybrid perovskite photovoltaics (PV) combine the promises of cost-effective solution printing with high power conversion efficiencies (PCEs) – already exceeding 25% in small scale perovskite solar cells (PSCs)[1,2]. Furthermore, the bandgap tunability of the perovskite material class to more than 2 eV make PSCs an ideal candidate for top cells of next-generation tandem PV[3]. However, despite these inherent advantages, the scale-up of the emerging technology poses a major challenge. The reason is the complex formation of the perovskite morphology from solution - involving solvent evaporation, crystal growth and nucleation[1]. High-quality perovskite absorber films feature a homogeneous, specularly-reflecting macrostructure and a polycrystalline microstructure of densely-packed nanometer to micrometer-sized crystal grains. For obtaining these morphological properties, the perovskite solution needs to be driven rapidly into supersaturation such that high nucleation rates are achieved and irregular crystal growth is suppressed[4]. In practice, this is achieved by so-called quenching methods - the most promising of which are antisolvent quenching, where the perovskite solution film is rinsed with an antisolvent[5], gas quenching, where the film is rapidly tried by forced convection over the substrate[6] and vacuum quenching, where the film is placed in a closed volume chamber whose gaseous content is rapidly pumped out[7]. Currently, record PSCs are fabricated on small scales using antisolvent quenching during spin coating, ejecting the antisolvent from a pipette on the still spinning substrate[8]. Unfortunately, this routine is fundamentally non-scalable and there is no protocol of how to transfer it to industrial-scale solution deposition such as slot-die coating, inkjet printing or spray coating. Astonishingly, the majority of literature on perovskite fabrication via quenching relies on qualitative description exclusively, although extensive knowledge on heat and mass transfer in chemical engineering is available[9,10]. A detailed analysis of mass transfer dynamics during quenching is missing, which represents a fundamental hurdle to transferability of engineering routines.

In this work, we present a complete analysis of mass transfer dynamics of all common quenching methods for the first time. We start by gas quenching where we have exactly provided and tested the exact dynamics in earlier works[11,12]. Herein, we provide a retrospective generalization including different air flow dynamics and solvent systems. We continue by modelling quenching in a vacuum chamber for the first time and find an astonishing degree of similarity with the gas quenching dynamics. The impact of the reduced chamber pressure is determined quantitatively both for the case of quenching at stabilized and exponentially decaying chamber pressure. To test the results, we measure chamber pressure and drying rate by in situ characterization. Lastly, we model the mass transfer caused by interdiffusion of antisolvent into a perovskite solution film during antisolvent quenching. To achieve quantitative relations, we experimentally determine the change of equilibrium concentration of the perovskite solution introduced an increasing ratio of antisolvent molecules. Finally, we compare all mass transfer dynamics quantitatively by determining the exact supersaturation apparent in the three quenching methods. We demonstrate further that supersaturation is the decisive benchmark of the effectiveness of the applied quenching method. In this way, we present a quantitative platform of comparability between all quenching methods for the first time. Via determination and comparison of supersaturation, it becomes possible to predict the impact of all process parameters on the quenching effectiveness. This predictability marks the critical step from fabricating PSCs as an art of qualitatively described trying-and-error recipes to a quantitative, scientific control model of PSC solution processing. This control model provides a new level of comparability of engineering recipes by maximum supersaturation values, such that large-area fabrication can be planned and modelled without the need of expensive test campaigns.