Automated Scalable Spray Coating of SnO2 for the Fabrication of Low-Temperature Perovskite Solar Cells and Modules

In the renewable energy field, the use of hybrid perovskite materials has opened up new directions to fabricate cost effective and highly efficient photovoltaic devices. Despite impressive power conversion efficiency (PCE), exceeding 25.2% [1], demonstrated on lab-scale devices (0.1 cm2), scalability and stability of device are still topical issues. In this context, large area deposition procedures and automatized fabrication protocols are required in order to achieve high throughput serial production of modules and panels. Tin oxide (SnO2) is a low-cost Electron Transport Layer (ETL) that it is commonly deposited by Spin-Coating [2, 3]. In this work, we demonstrated a first-ever spray coated SnO2 layer processed at low temperature for the realization of planar direct Perovskite Solar Cells (PSCs) and modules. This demonstrates that this is an effective scalable technique in producing perovskite solar devices. The devices employing sprayed SnO2 layer achieve an efficiency that is comparable with respect to that obtained using spin-coated one. We report on an efficient low-temperature solution-processed SnO2 nanoparticles in applications for ETL of PSCs. Using sprayed nano particles of SnO2 (Np-SnO2) as ETL, CH3NH3PbI3 based solar device showed a maximum PCE of 16.77% (avg. 15.01%) with respect to 17% (avg.15.5%) of spin coated Np-SnO2. Furthermore, long-term stability of devices has not worsened for the sprayed SnO2. Unencapsulated cells based on sprayed SnO2 stored in 25°C and 50% relative humidity showed shelf life stability by retaining 85% of the initial PCE value after more than 1000 hours. Similar behaviour was observed for the PCE of the spin coated SnO2 cells. Moreover, we demonstrated the feasibility of fabrication of the modules with 15cm2 active area which reached 9.37% of PCE from uniform spray deposited SnO2 film on large area 20×20 cm2. Additionally, by using Np-SnO2 we demonstrated the possibility of decreasing PSC fabrication temperature down to 100°C, that would be very attractive for flexible PSCs. This provides a viable route to easily combine low-cost, stability and high efficiency for the next generation perovskite photovoltaic devices