Abstract
The high crystal quality of formamidium lead bromide perovskite (CH(NH2)(2)PbBr3 = FAPbBr(3)) was infiltrated in a mesoporous TiO2 network. Then, high-quality FAPbBr(3) films were evaluated as active lasing media, and were irradiated with a picosecond pulsed laser to demonstrate amplified spontaneous emission (ASE), which is a better benchmark of its intrinsic suitability for gain applications. The behavior was investigated using two excitation wavelengths of 440 nm and 500 nm. Due to the wavelength-dependent absorbance spectrum and the presence of a surface adsorption layer that could be reduced using the shorter 440 nm wavelength, the ASE power dependence was strongly reliant on the excitation wavelength. The ASE state was achieved with a threshold energy density of ~200 mu J/cm(2) under 440 nm excitation. Excitation at 500 nm, on the other hand, needed a higher threshold energy density of ~255 mu J/cm(2). The ASE threshold carrier density, on the other hand, was expected to be ~4.5 x 10(18) cm(-3) for both excitations. A redshift of the ASE peak was detected as bandgap renormalization (BGR), and a BGR constant of ~5-7 x 10(-9) eV cm was obtained.