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

Abstract

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.