Tellurium-Based Double Perovskites A2TeX6 with Tunable Band Gap and Long Carrier Diffusion Length for Optoelectronic Applications

Lead-free hybrid perovskites have attracted immense interest as environmentally friendly light absorbers. Here, we report on tellurium (Te)-based double perovskites A(2)TeX(6) (A = MA, FA, or BA; X = Br- or I-; MA = CH3NH3; FA = CH(NH2)(2); BA = benzylamine) as potentially active materials for optoelectronic devices. These perovskites exhibit a tunable band gap (1.42-2.02 eV), a low trap density (similar to 10(10) cm(-3)), and a high mobility (similar to 65 cm(2) V-1 s(-1)). Encouragingly, the MA(2)TeBr(6) single crystal with a band gap of 2.00 eV possesses a long carrier lifetime of similar to 6 mu s and corresponding carrier diffusion lengths of similar to 38 mu m, which are ideal characteristics for a material for photodetectors and tandem solar cells. Moreover, A(2)TeX(6) perovskites are relatively robust in ambient conditions, being stable for at least two months without showing any signs of phase change. Our findings bring to the forefront a family of lead-free Te-based perovskites for nontoxic perovskite optoelectronics.