Perovskite solar cells based on screen-printed thin films

One potential advantage of perovskite solar cells (PSCs) is the ability to solution process the precursors and deposit films from solution^1,2. At present, spin coating, blade coating, spray coating, inkjet printing and slot-die printing have been investigated to deposit hybrid perovskite thin films^3-6. Here we expand the range of deposition methods to include screen-printing, enabled by a stable and viscosity-adjustable (40-44,000 cP) perovskite ink made from a methylammonium acetate ionic liquid solvent. We demonstrate control over perovskite thin-film thickness (from about 120 nm to about 1,200 nm), area (from 0.5 × 0.5 cm² to 5 × 5 cm²) and patterning on different substrates. Printing rates in excess of 20 cm s^-1 and close to 100% ink use were achieved. Using this deposition method in ambient air and regardless of humidity, we obtained the best efficiencies of 20.52% (0.05 cm²) and 18.12% (1 cm²) compared with 20.13% and 12.52%, respectively, for the spin-coated thin films in normal devices with thermally evaporated metal electrodes. Most notably, fully screen-printing devices with a single machine in ambient air have been successfully explored. The corresponding photovoltaic cells exhibit high efficiencies of 14.98%, 13.53% and 11.80% on 0.05-cm², 1.00-cm² and 16.37-cm² (small-module) areas, respectively, along with 96.75% of the initial efficiency retained over 300 h of operation at maximum power point.