Lattice dynamics of piezoelectric response of organic-inorganic hybrid perovskites

Hybrid organic-inorganic perovskites (HOIPs) exhibit substantial piezoelectric coefficients, holding significant potential as a cost-effective, environmentally benign, lightweight, and flexible piezoelectrics. However, the origin of such piezoelectric response in organic-inorganic ferroelectrics remains poorly understood. Here, we study the electron and ion components of piezoelectric tensors of (NEA)PbI3 (NEA = 1-(1-naphthyl)ethylamine) HOIPs, and reveal the contributions of atomic vibration modes and atomic groups to the internal-strain piezoelectricity. The combination of low vibrational frequencies and large mode amplitude in ions with significant Born effective charges amplifies the piezoelectric response of low-frequency modes to internal-strain mechanisms. When the mechanical strain changes the interaction between polar molecules and the Pb-I inorganic layers, the contribution of NEA molecules to piezoelectricity significantly increases. The tuning of this interaction can effectively regulate the piezoelectric properties of HOIPs, and thus expand their broader devices application.