Heterovalent Dopant Incorporation for Bandgap and Type Engineering of Perovskite Crystals

Controllable doping of semiconductors is a fundamental technological requirement for electronic and optoelectronic devices. As intrinsic semiconductors, hybrid perovskites have so far been a phenomenal success in photovoltaics. The inability to dope these materials heterovalently (or aliovalently) has greatly limited their wider utilizations in electronics. Here we show an efficient in situ chemical route that achieves the controlled incorporation of trivalent cations (Bi³⁺, Au³⁺, or In³⁺) by exploiting the retrograde solubility behavior of perovskites. We term the new method dopant incorporation in the retrograde regime. We achieve Bi³⁺ incorporation that leads to bandgap tuning (∼300 meV), 10⁴ fold enhancement in electrical conductivity, and a change in the sign of majority charge carriers from positive to negative. This work demonstrates the successful incorporation of dopants into perovskite crystals while preserving the host lattice structure, opening new avenues to tailor the electronic and optoelectronic properties of this rapidly emerging class of solution-processed semiconductors.