Bulk Incorporation of Molecular Dopants into Ruddlesden-Popper Organic Metal-Halide Perovskites for Charge Transfer Doping

Organic metal-halide perovskites (OHPs) have recently attracted much attention as next-generation semiconducting materials due to their outstanding opto-electrical properties. However, OHPs currently suffer from the lack of efficient doping methods, while the traditional method of atomistic doping having clear limitations in the achievable doping range. While doping with molecular dopants, has been suggested as a solution to this problem, the action of these dopants is typically restricted to perovskite surfaces, therefore significantly reducing their doping potential. In this study, successful bulk inclusion of "magic blue", a molecular dopant, into 2D Ruddlesden-Popper perovskites is reported. This doping strategy of immersing the perovskite film in dopant solution increases the electrical current up to approximate to 60 times while maintaining clean film surface. A full mechanistic picture of such immersion doping is provided, in which the solvent molecule facilitates bulk diffusion of dopant molecule inside the organic spacer layer. Physical criteria for judicious choice of solvents in immersion doping are developed based on readily available solvent properties. The immersion doping method developed in this study that enables bulk molecular doping in OHPs will provide a strategic doping methodology for controlling electrical properties of OHPs for electronic and optoelectronic devices.