High-performance semitransparent polymer solar cells floating on water: Rational analysis of power generation, water evaporation and algal growth

Compared to conventional ground-mounted photovoltaic (PV) cells, floating photovoltaic (FPV) cells open new opportunities for scaling-up solar power generation, especially in highly populated countries that may have competing uses for the available land. Large-scale FPV projects normally deploy old-fashioned crystalline silicon panels that are brittle and difficult to integrate. Polymer solar cells (PSCs) are regarded as a newer and more versatile concept that make quite a splash today. High absorption coefficients, thin active layers and tunable absorption spectra through a synergy of molecular and device engineering promote extensive research on the integration of semitransparent polymer solar cells (ST-PSCs) with smart architecture to deliver both practical and aesthetic benefits. In this work, we propose a new concept of extending ST-PSCs to the field of FPV cells and explore the potential of regulating aquatic environments and organisms. Three groups of high-performance ST-PSCs are fabricated. Maximum efficiency of 13% and average visible transmittance over 20% deliver an optimum trade-off between power generation and transparency among the best-performing ST-PSCs. We develop new experimental approaches and propose a feasibility study on the water evaporation and algal growth by placing the large-area ST-PSCs on bodies of water. To the best of our knowledge, we demonstrate for the first time that the specific transmittance windows with controlled light intensities generated by the ST-PSCs are capable of regulating water evaporation and algal growth, which provides insight into responsible scale-up of FPVs instead of simply blocking the sunlight. The new functions of ST-PSCs pave an intriguing prospect of developing ST-PSCs for practical FPV applications in the near future.