Efficient All Ambient‐Laser‐Annealed Perovskite‐Organic‐Photovoltaic Tandem Solar Cells

Abstract Laser annealing is versatile and useful with precise control for photovoltaic device fabrications. Here, its first application for fabricating perovskite tandem solar cells and organic photovoltaic (OPV) cells based on PM6:Y6 is reported, where PM6 is a donor–acceptor (D‐A) copolymer composed of the 4,8‐bis(5‐(2‐ethylhexyl)‐4‐fluorothiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene (BDT) and 1,3‐bis(thiophen‐2‐yl)‐5,7‐bis(2‐ethylhexyl)benzo‐[1,2‐c:4,5‐c’]dithiophene‐4,8‐dione (BDD) units and Y6 consists of dithienothiophen[3,2‐b]‐pyrrolobenzothiadiazole with 2‐(5,6‐Difluoro‐3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene)malononitrile units. In this work, all annealing steps were done by a CO 2 laser in the ambient for fabricating mixed self‐assembly‐monolayer type hole transport layer, wide bandgap 1.78 eV perovskite layer, and PM6:Y6 OPV absorber. The champion 1.78 eV perovskite device produces an impressive open‐circuit voltage ( V OC ) of 1.34 V and an efficiency of 20.2% with suppressed phase segregation. The first ambient laser annealed PM6:Y6 OPV cell produces a champion efficiency of 16.8% which is the highest for any laser annealed OPV cells reported. It is found that laser annealed PM6:Y6 films are smoother than the same film by conventional hot‐plate anneal, thereby enabling an improved PM6:Y6/C60 interface. Finally, the first laser‐annealed perovskite‐OPV champion device produces a short‐circuit current density ( J SC ) of 14.3 mA cm −2 , an V OC of 2.10 V, a fill factor (FF) of 79.6%, and an efficiency of 24.0%, comparable with the state‐of‐the‐art perovskite‐OPV tandem. The laser annealed tandems are more thermally stable than the cells fabricated by conventional hot‐plate anneal. This demonstrates the promising prospects of laser annealing which is more time efficient for the mass production of tandem solar cells.