Doping-Enhanced Visible-Light Absorption of CH3NH3PbBr3 by the Bi3+-Induced Impurity Band without Sacrificing a Band gap

Intrinsic organic-inorganic metal-halide perovskites have shown widespread applications in optoelectronic devices. Also, controllable doping is a very convenient route to tailor the performance of perovskites and endow them with new properties. Here, we add dopants into the perovskite precursor solution to achieve controllable incorporation of trivalent cations (Bi3+) into CH3NH3PbBr3 single crystals by using the inverse temperature crystallization method. A comprehensive spectroscopy study was performed. Although there is a significant red shift of the optical absorption after doping, the band gap of Bi-doped MAPbBr(3) crystals does not change. Bi3+ incorporation increases the density of states in the band gap, which can act as a scaffold for photon absorption with below-band gap light. This approach opens a promising route for the perovskite material design to obtain more light absorption without sacrificing the band gap, which gives a broad range of possibilities to photoelectric implications for the preparation of not only intermediate band gap photovoltaic devices but also tunable LEDs and so on.