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 MAPbBr(3) PSCs. In the structure of the MAPbBr(3) 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) MAPbBr(3) layers grown on the surface of undoped (p-type) MAPbBr(3) 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 MAPbBr(3) layers. The spectral response peaks redshift from 559 to 601 nm, with an increasing Bi doping level of 0% to 15%.