Plasmonic nanostructures for transparent photovoltaic facades

Building-integrated photovotaic facades can capture a significant amount of solar energy that is currently underused. Semitransparent photovoltaic devices are one of the most promising solutions for such applications. However, in conventional transparent photovoltaic structures, transparency inevitably translates to poor light harvesting and hence low power conversion efficiency. In this paper, we propose a plasmonic nanostructure based wavelength and angle selective back reflector that can provide excellent see-through clarity while providing effective light harvesting for efficient solar energy conversion. The proposed back reflector is independent from the solar cell design and can be integrated with nearly every type of transparent solar cell structures, ranging from amorphous to polymer absorbers and from single-junction to tandem cells. Uniquely, the plasmonic nanostructures can be integrated with a large-area thin-film solar cell device on flexible substrates, enabling “photovoltaic film” that can be retrofitted to the existing window systems. This paper presents the proposed concept and its validation using finite-difference-time-domain simulations. Results indicate that plasmonic light trapping can improve photovoltaic absorption of angled light by a factor of 1.7 on resonance while maintaining good transparency for normally incident light.