Sub-bandgap photon harvesting for organic solar cells via integrating up-conversion nanophosphors

• Strategy for application of UC to enhance performance of OPVs is developed.
• Jsc improvements of UC device were observed under IR laser and 1 sun illumination.
• This concept eliminates necessity to adapt the fabrication process of device itself.

Lanthanide-doped up-conversion nanophosphors were employed as up-conversion converters (UC-converters) combined with organic solar cells (OSCs). The optical properties of the external up-conversion layers were investigated, and the optimized layers were laminated with OSCs. Strong photocurrents were observed when OSCs with an UC converter were illuminated by a NIR laser. An improvement of photocurrent and efficiency were also observed under AM 1.5 G sun irradiation. Our investigations show a proof-of-concept that organic solar cells could utilize sub-bandgap photons via integrating up-conversion nanophosphors, which provide us a promising approach to exceed the efficiency limit of single junction organic solar cells.

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