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 MnBr₂, which effectively controls crystallization kinetics and restricts the nucleation of high n-phases, producing high-quality films. The resulting (BA)₂CsPb₂Br₇ (BA = C₄H₉NH₃) 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 Mn²⁺ 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.