Optimization of precursor concentration in formamidinium lead bromide thin films for perovskite-based light-emitting diode applications

Formamidinium lead bromide perovskite (FAPbBr3) are known as promising materials for light emitting diode (LED) applications in green range of electromagnetic waves due to their excellent optical and electrical properties and photoluminescence maxima located in 520–540 nm range. LED device performance based on FAPbBr3 is hindered by crystallinity of the film and morphological issues. In this study, we fabricated green FAPbBr3 LEDs using a two-step preparation method. We used thermal evaporation method to deposit PbBr2 films and then perovskite films were formed after spin coating FA solution on evaporated samples. By controlling the solution concentration, we obtained thin films with optimized morphology and grain size which resulted in LED device with green electroluminescence (EL). Turn-on voltage (and threshold voltage) is of importance. Lower threshold voltage and/or turn-on voltage is desirable for electronic devices. The EL spectrum has a full width at half-maximum (FWHM) parameter as narrow as 36 nm, a turn-on voltage of 2 V, and a luminance of 100 Cd cm−2. Moreover, the issue of color is very important in Pe-LED, and therefore, our finding is important. The novelty of the work is that to our knowledge, no one has obtained this value with the present synthesize method (Solution process method).