Phase-pure ferroelectric quantum wells with tunable photoluminescence for multi-state optoelectronic applications.

Quasi-two-dimensional (quasi-2D) metal halide perovskite (MHP) ferroelectrics, characterized by spontaneous polarization and semiconducting properties, hold promise for functional photoferroelectrics in applications such as optical storage and in-memory computing. However, typical quasi-2D perovskite films contain multiple quantum wells with random width distribution, which degrade optoelectronic properties and spontaneous polarization. Here, we introduce phase-pure quantum wells with uniform well width by incorporating the inorganic salt MnBr, which effectively controls crystallization kinetics and restricts the nucleation of high n-phases, producing high-quality films. The resulting (BA)CsPbBr (BA = CHNH) film demonstrates ferroelectric hysteresis behavior, clear in-plane ferroelectric domain switching, and a high photoluminescence quantum efficiency (PLQE) of 88.7%. Significantly, we observed a nonvolatile, reversible in situ photoluminescence (PL) modulation of Mn in this ferroelectric MHP film under an applied electric field, attributed to lattice distortion from ferroelectric polarization orientation. These findings enabled the development of a simple system comprising gallium nitride (GaN) light emitting diodes (LEDs) and ferroelectric films to implement multi-state signal encoding and a logic AND gate. This work advances the fabrication of efficient ferroelectric MHP films and highlights their potential for advanced optoelectronic applications.