Tunable color emission of boron nitride nanophosphors enabled by rare earth ions doping towards flexible luminescence application

Luminescent materials, particularly rare-earth (RE) ion-doped phosphors, have gained significant attention due to their wide applications in optoelectronics, lighting, photovoltaics, and sensing. Hexagonal boron nitride (h-BN) is a promising host for RE ion doping owing to its remarkable properties such as ultra-wide bandgap, optical transparency, thermal stability, and inertness. However, luminescent characteristics of these activator ions in h-BN remain unclear. Herein, we successfully synthesized h-BN nanophosphors doped with RE ions (Ce^3 +, Eu^3 +, and Tb^3 +). By adjusting the co-doping ratio, the h-BN nanophosphors exhibit bright emissions ranging from blue to green and red. White light emission was achieved at a doping ratio of [Ce^3 +]/[Eu^3 +]/[Tb^3 +] = 1/0.2/0.2. The luminescence lifetime in h-BN nanophosphors increased by 70,000 times compared to undoped BN. Doping states of RE ions and their energy levels correlating with the luminescent transition process were elucidated through experimental results and theoretical calculations. Additionally, flexible and transparent Polydimethylsiloxane (PDMS) films based on h-BN nanophosphors were fabricated, demonstrating different colors under ultraviolet (UV) light. These polymer-based fluorescent films possess excellent stretchability without compromising their luminescent properties. This work provides a feasible and effective strategy for fabricating h-BN nanophosphors, which is significant for rigid and flexible applications like optical displays, UV detection, information encryption, and anti-counterfeiting layers.