Influence of substrate temperature on the chemical, microstructural and optical properties of spray deposited CH3NH3PbI3 perovskite thin films

Influence of Deposition and Annealing Parameters on the Degradation of Spray-Deposited Perovskite Films

“…Samples prepared at higher deposition temperatures and shorter annealing times presented a similar behaviour, that is, the XRD patterns of the 24-h films deposited at 100 °C and 110 °C showed the monohydrate phase peaks only when the annealing time was less than 30 s, while those of the samples deposited at 120 °C presented the monohydrate phase peaks for annealing times below 10 s. The perovskite films that were annealed for the shortest period of time (100 °C for 30 s; 110 °C for 10 s and 120 °C for 5 s) degraded the most with almost no remaining traces of perovskite. XRD patterns of some of these samples, obtained right after deposition, are shown in a previous work 33 ; no monohydrate phase was observed in the films, confirming that it is due to humidity. On the other hand, films produced at higher temperatures and longer annealing times did not exhibit the monohydrate phase.…”

“…Therefore, samples annealed at higher temperatures during long times are more resistive to moisture infiltration because they have larger grains. Indeed, in a previous paper 33 we observed that grain size increased with annealing temperature, but SEM images of perovskite films deposited at 120 o C (Figure 2) indicates that grain size was not affected by annealing time.…”

“…A commercial spray gun, Steula BC 66-08 airbrush, with 0.8-mm nozzle size, was incorporated in a homemade automatic system to provide better reproducibility 33 . The system was based on a solenoid and a computer software, which was used to control the deposition time and pull the airbrush trigger.…”

“…Under these conditions, the thickness of the films was roughly 2 µm. Low deposition temperatures and short annealing times were chosen to avoid thermal degradation without compromising film crystallization 33 .…”

“…Although perovskite degradation has been extensively investigated, the correlation between the manufacturing process and the degradation mechanism is not well understood. In a previous work 33 , we determined the best conditions to rapidly deposit and crystallize sprayed CH 3 NH 3 PbI 3 perovskite thin films in a single step. Crystalline films with high coverage and large equiaxed grains (4-5 μm) were obtained in a very short annealing time (30 s) at 120 °C.…”