Charge Transfer Doping of Ruddlesden–Popper Metal–Halide Perovskites via Bulk Incorporation of Organic Molecular Dopants

Ruddlesden–Popper metal–halide perovskites have recently attracted much attention as next-generation semiconducting materials due to their outstanding opto-electrical properties. However, these low dimensional materials critically suffer from relatively poor electrical conductivity, which is challenging to tune with traditional method of bulk atomistic doping. While doping with molecular dopants, a family of versatile dopants for molecular design has been suggested as a solution to this problem.[1,2] Nonetheless, the action of these dopants was typically restricted to perovskite surfaces, therefore significantly reducing their doping potential. In this study, we report successful bulk inclusion of ‘magic blue’, a molecular dopant, into two-dimensional (2D) Ruddlesden–Popper perovskites.[3] Our doping strategy of immersing the perovskite film in dopant solution increased the electrical current up to ~60 times while maintaining clean film surface. We provide a full mechanistic picture of such immersion doping, in which the solvent molecule facilitates bulk diffusion of dopant molecule inside the organic spacer layer, based on the optimum solvent processing. The immersion doping method developed in this work which enables bulk molecular doping in metal–halide perovskites in general will provide a strategic doping methodology for controlling electrical properties of low dimensional metal–halide perovskites for electronic and optoelectronic devices.<br/><br/><b>References </b><br/>[1] E. Ashley Gaulding et al., <i>Adv. Mater.</i> <b>31</b>, 1902250 (2019).<br/>[2] A. L. Abdelhady et al., <i>J. Phys. Chem. Lett.</i> <b>7</b>, 295 (2016).<br/>[3] J. Lee et al., <i>Adv. Funct. Mater.</i> 2302048 (2023).