Researchers Unlock Path to Cheaper, More Efficient Organic Solar Cells

Organic solar cells offer a promising method to convert light into fossil-free energy, yet their performance still cannot compete with their silicon counterparts. Recently, strong exciton-photon coupling has been shown to enhance the properties of organic solar cells. The strong coupling regime is reached by confining the electromagnetic field into a mode that is spatially overlapping and in-resonance with a molecular transition. Traditionally, confining electromagnetic fields requires the use of mirrors, which reduce molecular absorption, thereby diminishing the usefulness for solar cell applications. In this study, angular resolved reflectivity and transfer matrix simulations show that the strong coupling regime can be reached in conventional organic solar cells by using the refractive index contrast between layers, thereby eliminating the need for additional mirrors. By adjusting anode materials and active layer thicknesses, strongly coupled solar cells can achieve efficiencies up to 13.4%. This value is more than twice as high as strongly coupled solar cells prepared with mirrors. The findings introduce a method for implementing the strong coupling regime in organic solar cells without compromising the ability of the system to absorb light, paving the way for strong coupling empowered devices and presenting alternatives for the production of clean energy.