Singlet fission photovoltaic cells as dual-wavelength laser power converters compatible with highly efficient solar cells

I applied photovoltaic cells equipped with singlet fission (SF) of molecular systems to dual-wavelength laser power converters (DW-LPCs) that efficiently convert two laser lights of different wavelengths to electricity. When the SF-DW-LPC is illuminated by eye-safe laser light of 1470 nm wavelength emitted from a laser diode, a single photon is converted to a single carrier. On the other hand, a single high-energy photon emitted from a high-power and low-cost laser diode of 808 nm is converted to two carriers by SF owing to its endothermic feature, even though the photon energy is slightly lower than twice the fundamental energy gap. Furthermore, the SF-DW-LPC operates as a highly efficient solar cell. These functions are required for optical wireless power transmission to moving objects including electric vehicles and flying drones. I modeled the photovoltaic process with SF and evaluated the limiting conversion efficiencies by detailed-balance calculations. Conversion efficiencies of the SF-DW-LPC for these two laser lights are competitive with those of the conventional single-junction LPCs dedicated to these wavelengths, respectively. The efficiency under solar light is close to that of the optimally designed SF solar cell. Furthermore, the SF-DW-LPC outperforms other types of DW-LPCs designed on the basis of intermediate band, triplet–triplet annihilation, and multiple exciton generation solar cells. Endothermic SF and carrier/energy extraction into the neighboring acceptors have already been demonstrated. However, molecular systems that apply to 1470 nm have not yet been realized, which is the top-priority issue to be solved to realize highly efficient SF-DW-LPCs.