Polymer modulated ink rheology and compatibility enables homogenized printing of a Spiro-OMeTAD transport layer for scalable and stable perovskite solar modules

The realization of fully printed preparation of perovskite solar modules is essential for scalability. However, the printing process and film-forming properties of organic transport layers, especially Spiro-OMeTAD, have always been neglected. Printed Spiro-OMeTAD suffers from inhomogeneity and pore problems due to the mismatch between ink rheology and the printing process as well as the instability of LiTFSI-tBP additives. In this work, a polymer modification strategy of adding poly(4-vinylpyridine) to Spiro-OMeTAD solution is proposed to increase the internal friction of the printing process. The undue capillary flow and Marangoni flow are inhibited, which can achieve a homogenized deposition of large-area Spiro-OMeTAD films. Furthermore, the pyridine group of polymers can immobilize and stabilize LiTFSI to resolve the pore effect during the film formation process. We achieved a photovoltaic conversion efficiency (PCE) of over 24.2% for a device on a lab scale, which is the highest efficiency of fully functional-layer printed devices. Based on this strategy, large-area perovskite solar modules show a champion PCE of 18.16% and 16.34% on an aperture area of 25 cm2 and 100 cm2, respectively. Unencapsulated devices maintain more than 80% of their original efficiency after 1300 h of airborne water-oxygen attack and about 1000 h of thermal aging. By improving the rheological properties of Spiro-OMeTAD, we achieved fully functional layer-printed perovskite solar cells with record-high efficiencies.