Biogenic fluorescent protein–silk fibroin phosphors for high performing light-emitting diodes†
This work presents a new family of bio-hybrid light-emitting diodes (Bio-HLEDs) using all-bio color down-converting coatings that combine silk fibroin (SF) as a packaging matrix and fluorescent proteins (FPs) as emitters. The thermal, mechanical, optical, and luminescent features of the FP–SF bio-phosphors were optimized with respect to the blend composition and the FP stability under thermal and irradiation stress. Bio-HLEDs with FP–SF filters feature stabilities of 1.2 h and 500 h (200 mA) at efficiencies of ∼40 lm W−1 for on-chip and remote configurations, respectively. This is significantly superior to devices with FP–polymer bio-phosphors – i.e., 1.8 min (on-chip) and 300 h (remote) at <35 lm W−1. The excellence of the biogenic phosphors is attributed to (i) the ideal optical features of the SF films, (ii) the highly efficient emission of the FPs, and (iii) the high thermal- and photo-stabilities of FPs in the SF matrix. Finally, we revealed that the emission deactivation process of FP–SF phosphors is related to a very slow protonation of the ionic form of the FP chromophore along with large morphological changes due to thermal- and photo-induced FP motions. Overall, this work shows the promising prospects of fully biogenic phosphors en route to designing highly stable bio-based lighting devices.