The photoluminescence (PL) of rare-earth-doped materials is predominantly controlled by the local crystal field symmetry around rare-earth ions. Using electric fields (E) to modify the PL properties is particularly intriguing as it is compatible with modern electronics and is promising for advanced applications in optical information storage and communication. It is reported that the E-induced structural evolution in host ferroelectrics (FEs) can effectively manipulate the crystal field environment surrounding rare-earth ions, consequently enabling a dynamic modulation of PL intensity (i.e., the E-PL effect). However, the hysteresis behavior in FEs limits the PL modulation range. Antiferroelectrics (AFEs) show a reversible AFE-FE phase transform with zero remanent polarization, particularly promising for realizing reversible E-PL modulation with large tunability. In AFE thin films, the clamping effect from the substrate may exert a significant influence on the structural evolution during the E-induce phase transition. Therefore, compared with the ceramic forms, it is possible to analyze distinct E-PL behavior in rare-earth doped AFE thin films.

1% Er³⁺-dopedPb_0.98La_0.02Zr_0.95Ti_0.05O₃ (PLZT-Er) thin films were prepared on Pt/Ti/SiO₂/Si substrates by a sol-gel/spin-coating method with lead acetate trlhydrate (PbC₄H₆O₄·3H₂O, 99.99%(379.33), Aladdin Co., China), lanthanum nitrate hexahydrate (LaN₃O₉·6H₂O, 99%(433.03), Aladdin Co., China), erbium trinitrate pentahydrate (Er(NO₃)₃·5H₂O, 99.9%(443.37), Aladdin Co., China), zirconium propoxide (C₁₂H₂₈O₄Zr, 70%(327.56), Aladdin Co., China), and titanium butoxide (C₁₆H₃₆O₄Ti, ≥99.0%(340.32), Aladdin Co., China) as the raw materials. The crystal structure was characterized by X-ray diffraction (XRD, Ultima III, Rigaku Co., Japan). The surface morphology was observed using atomic force microscopy (AFM, ICON, Bruker Co., Germany). The polarization (P-E) and current (I-E) loops were measured by a ferroelectric analyzer (AIX ACT, TF2000) at 1 kHz. The down-conversion photoluminescence (DCPL) emission spectra were measured by fluorescence spectroscopy (ULS2048x64TEC, Avantes Co., the Netherlands) under 405 nm and 532 nm laser excitation. For the E-PL tests, 20 nm-thick transparent indium tin oxide (ITO) top electrodes were deposited on the surfaces of PLZT-Er thin film by magnetron sputtering in argon atmosphere (2.0 Pa) at 320 wd3.

The structural, PL, and E-PL properties of PLZT-Er AFE thin films are systematically investigated. The XRD patterns confirm a pure perovskite structure with a lattice shrinkage due to the substitution of Er³⁺ at A-sites, whereas the AFM analysis reveals a smooth surface with a roughness of approximately 3 nm. The double P-E loop and characteristic I-E peaks verify the AFE nature of PLZT-Er thin films, with reversible AFE→FE transitions at ±452 kV·cm^-1 and FE→AFE transitions at ±199 kV·cm^-1. Under 405 nm excitation, the PLZT-Er exhibits 487 nm (⁴F_7/2→⁴I_15/2) and 610 nm (⁴F_9/2→⁴I_15/2) emissions, whereas an excitation at 532 nm induces 560 nm (⁴S_3/2→⁴I_15/2), 660 nm (⁴F_9/2→⁴I_15/2), and 850 nm (⁴S_3/2→⁴I_13/2) emissions, all originating from efficient energy transfer and relaxation of Er³⁺ ions. The reults of E-PL tests demonstrate a remarkable reversible modulation. In 830 kV·cm^-1, the emission at 487 nm shows an 85.14% reduction, with stable switching over six cycles. This performance outperforms PLZT-Er ceramics (+30% modulation) and most reported FE/AFE materials, which is attributed to their higher breakdown strength. The opposite E-PL tuning compared to PLZT-Er ceramics is explained by increased local crystal field symmetry around Er³⁺ ions, arising from either substrate clamping-induced antiferroelectric orthorombic →ferroelectric orthorombic phase transition or incomplete ferrielectric→antiferroelectric transition in an insufficient electric field. These findings highlight the PLZT-Er thin films as promising candidates for optical information storage and communication devices.

Er³⁺-doped Pb_0.98La_0.02Zr_0.95Ti_0.05O₃ (PLZT-Er) thin films exhibited a reversible electric-field-modulated photoluminescence (E-PL) effect. Under 405 nm laser excitation, a PL reduction of -85% could be achieved in an applied electric field of 830 kV·cm^-1. This negative E-PL tuning trend was anomalously opposite to that in bulk PLZT-Er ceramics. Two potential mechanisms could be proposed to explain this anomalous phenomenon, i.e., either the antiferroelectric orthorombic (AFE_O) to ferroelectric orthorombic (FE_O) phase transition or the incomplete ferrielectric (FiE) to antiferroelectric (AFE) phase transition in PLZT-Er thin films could increase the local crystal field symmetry around Er³⁺ ions.