Dissociative Host-Dopant Bonding Facilitates Molecular Doping in Halide Perovskites

Molecular doping is a promising strategy to fine-tunethe electronicproperties of halide perovskites and accelerate their implementationin next-generation optoelectronics. However, a deeper understandingof the role of host-dopant interactions in these systems is neededto fully exploit the potential of this avenue. Herein, we demonstratea surface post-treatment strategy employing n-type molecular dopantn-DMBI-H to modulate free hole density in p-type CH3NH3Sn0.75Pb0.25I3 films. Weshow that the adsorption of n-DMBI-H on surface Sn atoms, followedby the dissociation of an electron-donating hydride from the dopant,facilitates charge transfer to the perovskite and hole trapping atthe dissociated hydride. We identify this mechanism as a key factordictating doping compensation in perovskites, allowing carrier densitycontrol within nearly 1 order of magnitude via the dissociated moleculardopant located at film surfaces and grain boundaries. We then exploitn-DMBI-H in perovskite/transport layer junctions, achieving reducedcarrier losses and improved contact selectivity and performance inp-i-n, Sn-rich perovskite solar cells. We expect this work to providecarrier density tuning guidelines for a broad range of tin-based perovskiteapplications.