Soft Dopants for a Soft Lattice: Toward Electronic Doping Control in Metal Halide Perovskite Quantum Dots

Electronic doping control in semiconductors is essential for engineering optoelectronic properties yet remains elusive for metal halide perovskite quantum dots (MHP QDs). This perspective assesses the current state of aliovalent substitutional doping in MHP QDs and concludes that the softness of the MHP lattice drives both native defect compensation and thermodynamic phase separation, rendering conventional inorganic dopants ineffective. Instead, we propose soft organic dications as a viable new class of persistent donor dopants for MHP QDs. The distinct optical signatures of majority carriers in QDs make optical spectroscopy a powerful screening tool for electronic doping. In a case study of natively intrinsic and self-p-doped MHP QDs, the orthogonal optical responses upon post-synthetic A-site substitution provide first indications for organic dications as viable donor dopants.