Boosting Uniformity and Efficiency of Large-Area Inverted Organic Photovoltaics Via ZnO Surface Energy Modulation

Large-area organic photovoltaic modules have a wide range of applications in a number of fields due to their unique advantages. Inverted organic solar cells exhibit better air stability and are suitable for all-air printing of large-area modules. However, the mismatch between the surface energy of ZnO and the active layer leads to coffee rings and stick-slip effects during the printing process, resulting in uneven deposition of the active layer. Additionally, the mismatch in energy levels between the active layer and ZnO degrades device performance. Hence, a phenol series of alcohol solutions is utilized to improve the wettability and surface energy of ZnO, enabling the formation of large-area homogeneous active layer films. Hydroxyl groups in the phenol series passivate ZnO surface defects and form hydrogen bonds with small molecules of the acceptor, increasing carrier mobility and improving device performances. Based on the PM6: BTP-eC9 (o-XY) system, the power conversion efficiency (PCE) reaches 18.80% for small-area devices and 15.87% for large-area modules, higher than the forward structure (15.83%). This study offers an effective approach to mitigating large-area active layer film uniformity issues, advancing the preparation of large-area organic photovoltaic modules via all-air printing. The excellent wettability reduces the resistance of active layer solution in the spreading process, which effectively suppresses the coffee ring effect during large-area printing, thus obtaining homogeneous green-printed large-area active layer films. Therefore, excellent PCEs of 18.80% and 15.87% are harvested by the interface optimization strategy based on PM6:BTP-eC9 system with the areas of 0.04 and 25 cm2, respectively. image