Lead-Free Semiconducting Organic–Inorganic Hybrid Perovskite with Mixed Organic Cations

Hybrid perovskites with mixed organic cations have recently received extensive focus from researchers for their structural tunability, enhanced performance, and stability. However, because there are certain requirements for the size of different organic cations to form hybrid perovskites with mixed organic cations, reports on hybrid perovskites that can contain both phosphonium and ammonium cations have been rare. Here, we report an organic–inorganic hybrid perovskite (Me3PCH2CH2CH3)2(CH3CH2CH2NH3)Sb2Br9 (1) with [Me3PCH2CH2CH3]+ cations and [CH3CH2CH2NH3]+ cations. Compound 1 exhibits a reversible phase transition at 371.3/353.2 K. Compared with the organic–inorganic hybrid perovskites only with [Me3PCH2CH2CH3]+ cations or [CH3CH2CH2NH3]+ cations, the phase transition temperature of the organic–inorganic hybrid perovskite formed by mixing [Me3PCH2CH2CH3]+ cations and [CH3CH2CH2NH3]+ cations is significantly increased, and the thermal stability is improved. Structural analysis shows the disorder of [CH3CH2CH2NH3]+ cations and the twisting motion of [Me3PCH2CH2CH3]+ cations and the inorganic skeleton are the major reasons for the phase transition of 1 at high temperatures. Furthermore, 1 possesses semiconductor properties with an optical band gap of 2.945 eV. This discovery will shed light on exploring more excellent functional perovskite materials with mixed organic cations.