During last two decades hybrid organic/inorganic solar cells have been developing in several forms, such as perovskite solar cell (PSC) technology that is one of the most promising in terms of power conversion efficiency (PCE) [1]. Among the several still opened issues, the main challenges regard the scalability of the device from lab-scale to the module dimensions that requires manufacturing processes automatization. Indeed, in order to promote PSC technology towards industry standards, performance reproducibility should be ensured by guaranteeing spatial uniformity of the different layers deposited on large area substrates. As a result, a repeatable scaled-up process necessarily implies the employment of automatized machines. Usually, an effective blocking layer is deposited quickly by aerosol spray pyrolysis [2], normally performed by manual airbrush deposition. This work focuses on automatically in-air spray coating deposition of the TiO₂ blocking layer (bl-TiO₂) in the conventional mesoscopic direct architecture (FTO/bl-TiO₂/m-TiO₂/CH₃NH₃PbI₃/spiro-MeOTAD/Au). In this approach, first we demonstrated high uniformity in terms of electrical performances, over a large array (125 cm²) of 20 substrates, each containing a large area cell (> 1 cm²). The devices realized with an automatized spray pyrolysis at 460 °C, shown an average PCE = (15.4 ± 0.5) % with a maximum of 15.9 % and with an average blocking layer thickness θ = (65 ± 10) nm.

In order to improve the scalability of the process in terms of productivity, maintaining uniformity on large area and repeatability, the automatized deposition of the blocking layer was implemented by performing the spray process at low temperature (90°C). In this approach, we changed drastically the set of parameters within the machine, such as number of layers, speed of the recycle, pressure of jet and path of deposition. At the same time, we modified the electron transport layer (ETL) fabrication process by subsequently depositing bl-TiO₂ and m-TiO₂ and then sintered together at 480°C.

The average resulting device PCE was (14.9 ± 0.4) % with a maximum of 15.3%, comparable with those of high-temperature processed ones and with an average blocking layer thickness θ = (70 ± 10) nm. The proposed process allowed halving the number of the sintering processes and consequently reducing energy, time and material consumption. Thus, the developed deposition method paves the way for ETL large-scale production employed in the most efficient reported in literature PSC based on mesoscopic architecture [1].