Development of highly transparent interference structural colour pigments for aesthetic and efficient BIPV modules

Building-integrated photovoltaic (BIPV) technology enhances renewable energy utilization and taps buildings’ energy savings potential, offering significant environmental benefits. However, conventional photovoltaic (PV) modules are limited by their monochromatic appearance, mainly installed on rooftops and leaving facades underutilized, impeding the advancement of BIPV facade systems. This study proposes a novel solution using highly transparent interference-type structural colour pigments (SCP) to achieve coloured PV modules, followed by computational and experimental methods to investigate SCP’s chromatic characteristics and coloured PV performance. The simulation of structural colours is first conducted by the transfer matrix method, which facilitates the synthesis and preparation of two distinct types of SCP, i.e. three-layer TiO2/mica/TiO2 (M/T) and five-layer SiO2/TiO2/mica/TiO2/SiO2 (M/T/S). The structural colours of SCP exhibit a clockwise shift on the horseshoe diagram with increasing coating thickness and show colour differences when surrounded by materials of different refractive indices, consistent with simulation results. The coloured glass sheet prepared by screen printing exhibits a high optical transmittance, with the M/T/S sample achieving approximately 67.0% ∼ 89.8% across 400 ∼ 1200 nm. Furthermore, the PV modules prepared with two types of SCP exhibited high-efficiency retention rates of at least 91.6% and 94.9%, respectively. The SCP feature simple preparation, adjustable colouration, and high transmittance, with minimal reflection outside the visible light band, meeting PV colourization requirements.