Bismuth-doping induced red-shifted spectral response of homo-epitaxial MAPbBr3 photodiodes

Perovskite single crystals (PSCs) photodiodes with p–n junctions have been widely studied due to their effective blocking of injected current with barriers and quickly separating the electrons and hole pairs with a built-in electric field. Here, we report a solution-processed epitaxial (SPE) growth method to fabricate p–n photodiodes based on MAPbBr3 PSCs. In the structure of the MAPbBr3 PSCs, bismuth donor doping will change the conduction type from p-type to n-type and redshift the absorption edge along with the increase in Bi concentration. Therefore, this work successfully fabricates the p–n photodiodes with homo-epitaxial Bi-doped (n-type) MAPbBr3 layers grown on the surface of undoped (p-type) MAPbBr3 PSCs substrates through the SPE growth method. The p–n photodiodes achieve a tunable spectral response by simply adjusting the Bi doping concentrations of homo-epitaxial MAPbBr3 layers. The spectral response peaks redshift from 559 to 601 nm, with an increasing Bi doping level of 0% to 15%.