Epitaxially Grown Li + ‐Conductive Li 0.33 La 0.5567 TiO 3 :Yb 3+ ,Er 3+ Thin Film Enabling Ion‐Migration‐Driven Modulation of Upconversion Luminescence for Potential Electro‐Optical Memory Emitter

ABSTRACT Lanthanide‐doped luminescent materials exhibiting electric field‐modulated optical emission have shown considerable potential in optoelectronic applications. In contrast to lanthanide‐doped ferroelectric‐based systems, this study presents an epitaxially grown Li + ‐conductive Li 0.33 La 0.5567 TiO 3 :Yb 3+ ,Er 3+ thin film that demonstrates real‐time, reversible modulation of Er 3+ upconversion luminescence (UCL) via a unique mechanism based on electric field‐driven Li + ion migration, which also imparts temporal memory functionality. Through comprehensive theoretical simulations, time‐of‐flight secondary ion mass spectrometry and frequency‐dependent electro‐optical measurements, the hopping of Li + ions and vacancies under applied electric fields has been identified as the dominant mechanism controlling the low‐frequency modulation of luminescence. Directional Li + migration causes their progressive accumulation at the interface between the indium tin oxide (ITO) electrode and the thin film, thereby altering the local chemical environment surrounding Er 3+ ions and modulating the UCL. This ion‐migration‐driven modulation underscores the potential of such device to operate as an electro‐optical memory emitter.