• • The co-doped Cs3GdCl6 microcrystals exhibit a 2.3-fold increase in integrated NIR-II emission intensity from 298 K to 373 K, directly addressing thermal quenching limitations in conventional phosphors.
• • Energy transfer efficiency from Sb3+ to Er3+ reaches 86% at room temperature and increases further with temperature, enabling efficient sensitization of NIR-II emission.
• • The material demonstrates high photostability, retaining 95% of initial emission after 120 minutes of continuous UV irradiation, suitable for long-term operation in bioimaging and communication devices.
• • A proof-of-concept wireless optical communication link using the microcrystals achieves a signal-to-noise ratio of 30 dB at 400 Hz modulation, indicating practical viability for NIR-II optical communication.