Cubic Cesium Lead Bromide Stabilized by Ethylammonium Incorporation

Lead halide perovskites are widely studied as semiconductors for optoelectronic applications, in particular, for solar cells and room temperature radiation detectors. Although many lead halide perovskite compounds exhibit excellent properties, achieving their optimal performance is hindered by structural distortion from an ideal cubic to orthorhombic or monoclinic symmetries. To address this issue and stabilize the cubic structure in CsPbBr₃, we employed ethylammonium cation to form a series of Cs_x(EtNH₃)_1-xPbBr₃ solid solutions. We found that, unlike the widely utilized formamidinium CH(NH₂)₂⁺ that has been previously reported to stabilize up to ≈30% Cs⁺ content, larger ethylammonium EtNH₃⁺ cation increases the incorporation of Cs⁺ up to 65% while maintaining the cubic structure. The resulting samples exhibit increased stability in humid air and show only slight signs of decomposition onset in 24 h. Optical measurements determined a bandgap of 2.27 eV for Cs_0.65(EtNH₃)_0.35PbBr₃, which is almost the same as that of pristine CsPbBr₃, indicating that the optoelectronic properties of the resulting phase remain largely unchanged. Electrical property measurements confirm a large resistivity of 40.1 MΩ·cm in the resulting phase for a pressed pellet sample.