The application of fluorescent proteins (FPs) in optoelectronics is hindered by the need for effective protocols to stabilize them under device preparation and operational conditions. Factors such as high temperatures, irradiation, and organic solvent exposure contribute to the denaturation of FPs, resulting in a low device performance. Herein, we focus on addressing the photoinduced heat generation associated with FP motion and rapid heat transfer. This leads to device temperatures of approximately 65 °C, causing FP-denaturation and a subsequent loss of device functionality. We present a FP stabilization strategy involving the integration of electrostatically self-assembled FP-apoferritin cocrystals within a silicone-based color down-converting filter. Three key achievements characterize this approach: (i) an engineering strategy to design positively supercharged FPs (+22) without compromising photoluminescence and thermal stability compared to their native form, (ii) a carefully developed crystallization protocol resulting in highly emissive cocrystals that retain the essential photoluminescence features of the FPs, and (iii) a strong reduction of the device's working temperature to 40 °C, leading to a 40-fold increase in Bio-HLEDs stability compared to reference devices.
Keywords: biohybrid lighting; color down-conversion; luminescent protein cages; protein-cocrystals; supercharged fluorescent proteins.