Inkjet-Printed Flexible Semitransparent Solar Cells with Perovskite and Polymeric Pillars

Semitransparent perovskite solar cells are important for building-integrated photovoltaics. Most research is focused on glass substrates, which can be utilized as glass windows during the construction of the buildings. Herein, the fabrication of flexible and semitransparent perovskite-based solar cells is presented, which can be used for existing windows as retrofitting process. The transparency of the cells is obtained through printing transparent and noncolored “optical holes” at micrometric dimensions. The fabrication approach is based on inkjet printing pillars composed of polymerized N-vinylcaprolactam, followed by inkjet printing of a perovskite layer, to attain a digitally tuned semitransparency, all performed in open air. The printing compositions are tailored, including the solvents with a controlled volatility, and adding a surfactant to fit both the inkjet printing process and the vacuum-assisted perovskite crystallization. The flexible semitransparent solar cells achieve a power conversion efficiency (PCE) of 9.14%, with an average transmittance of 29.3%. Beyond transparency, the pillars also contributed to the mechanical properties: bending measurements reveal that the device without the pillars retains 71.4% of the PCE after 300 cycles compared to the pillared device which retains 90% of its initial PCE after 500 bendings.