Effects of Spin-Casting Speed on Solar Cell Performances and Corresponding Films Morphology and Optical Properties Using 2D Perovskite of PEA2MA2Pb3I10

On hot substrates with a temperature of 100 °C, the qualities of two-dimensional perovskite PEA2MA2Pb3I10 (PEA = phenethylammonium, MA = methylammonium) films have been explored which are constructed with different spin-casting speeds. These films are performed at the speed of 1000, 2000, 4000, and 6000 revolution per minute (RPM). Below 4000 r, a higher RPM results in higher crystalline quality with more uniform morphology. Correspondingly, 4000 r devices show better performance on average (4.3% power conversion efficiency) and less hysteresis in the J-V curve than 1000 r (3.6%) and 2000 r devices (3.4%). However, for devices that were fabricated at 6000 r, inferior performance (2.8% on average) may not be predicted simply by the morphology characterization or optical measurement results at room temperature; instead, carrier trapping states can occur that result in thermally activated PL below 200 K with an activation energy of 18 meV, which do not occur in the 1000 r, 2000 r, and 4000 r films. Our results suggest that for evaluating 2D perovskite films prior to fabricating optimal devices, multiple morphology characterizations and optical measurements, including of low-temperature PL, will be helpful. Graphical Abstract Integrated PL intensity as a function of the inverse temperature of 1000 r, 2000 r, 4000 r and 6000 r, respectively, shows that optical measurements (especially low-temperature PL) are needed if we want to directly linked the optical properties of perovskite materials to the performances of corresponding devices.