Improved photon absorption in dye-functionalized silicon nanocrystals synthesized via microwave assisted hydrosilylation

Herein, we report a method to produce luminescent silicon nanocrystals (SiNc) that strongly absorb ultra
violet–visible light (300–550 nm) and emit in the near-infrared range (700–1000 nm) with a high photo
luminescence quantum yield (PLQY). Using microwave-assisted hydrosilylation and employing reactive
chromophores– such as ethenyl perylene, ethynyl perylene and ethylene-m-phenyl BODIPY– we are
able to achieve a 10- and 3-fold enhancement of the absorption in the blue and green spectral range,
respectively. The investigated dyes function both as passivating agents and highly efficient antenna, which
absorb visible light and transfer the energy to SiNc with an efficiency of >95%. This enhanced absorption
leads to a significant photoluminescence enhancement, up to ∼270% and ∼140% under excitation with
blue and green light, respectively. Despite the gain in absolute brightness of the emission, we demon
strate that back energy transfer from the SiNc to the dyes leads to a decrease in the PLQY for dye
modified SiNc, as compared to unmodified SiNc. The synthesis of the SiNc-dye conjugates opens up new
possibilities for applications of this abundant and non-toxic material in the field of solar energy harvesting,
optical sensing and bioimaging via achieving strong NIR PL excited with visible light