Ambipolar Charge Carrier Transport Properties at the S-Benzyl-l-cysteine-Induced 2D/3D Halide Perovskite Interface

We fabricated a 2D/3D perovskite film by adding a molecular spacer, S-benzyl-l-cysteine (SBLC), during MAPbI(3) perovskite film formation and investigated the effect of SBLC on the electronic conduction with a field-effect transistor. The addition of SBLC resulted in a larger grain size on the top surface and activated the electronic conduction modulated by the gate electric field. The field-effect modulation is attributed to the presence of the 2D perovskite surface layer induced by the SBLC molecular spacer on the 3D MAPbI(3) perovskite bulk, resulting from the passivation of interfacial localized states and suppression of ion migration within the MAPbI(3) perovskite film. Illumination with green light activated hole transport, resulting in ambipolar transport in the SBLC-induced MAPbI(3) perovskite 2D/3D film, explaining that the SBLC treatment reduced the hole trap density of states. Illumination with green light maximized the effect of the surface 2D layer of the 2D/3D MAPbI(3) perovskite film on the field effect-induced charge transport, enabling ambipolar electronic transport with the 2D/3D configuration due to suppression of the ionic behavior on the surface. This study highlights the electronic and structural effects of the organic molecular spacer on the electrical properties of the 3D bulk layer, hinting that defect-induced electronic and structural instability in the 3D bulk can be overcome by the passivation of the 3D bulk surface by the formation of the 2D/3D perovskite interface.