Ultrafast and Scalable Laser-Induced Crystallization of Titanium Dioxide Films for Planar Perovskite Solar Cells

A conventional annealing method to fabricate metal oxide films used for perovskite solar cells (PSCs) is a time-consuming batch process. Herein, a near-IR fiber laser process with a unique design of power ramping program and beam configuration is developed to achieve ultrafast and scalable processing of TiO ₂ films for PSCs. Highly crystalline anatase TiO ₂ films can be synthesized in only 18.5 s by the laser process with a peak annealing temperature up to 800–850 °C, compared with that of the furnace-annealing at 500 °C for 30 min and an overall processing time of 3 h. Then, a unique capability of using this laser process is presented to anneal stacked layers of substrates coated with the TiO ₂ films simultaneously, with a uniform annealing area up to 15.2 cm ², thereby potentially achieving an in-line production rate of over 43 cm ² min ⁻¹ (1 cm ² in ≈1.4 s). Planar PSCs fabricated under a high relative humidity of 60–70% based on the TiO ₂ films annealed under optimal laser conditions show enhanced photovoltaic performance than the furnace-annealed samples. This laser process potentially opens a new avenue for scalable annealing and rapid production of thin films.