Highly Stable Organic Solar Cells with Fullerenol as Interfacial Compatibilizer

The emerging technology of organic solar cells faces challenges related to long-term durability due to the combined effects of moisture, thermal, and photo stresses. To address this issue, we introduced a novel interfacial stabilizer, fullerenol, C₆₀(OH)_x, which substantially improved the durability of organic solar cells to cope with environmental stress. This study utilized X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy to confirm that C₆₀(OH)_x forms hydrogen bonds with both the oxygen atoms of ZnO and the fluorine atoms of Y6. As a result, the compatibility and charge transport between the electron transport layer (ETL) and the organic photoactive film were significantly improved, thereby stabilizing the interface. By incorporating the ZnO/C₆₀(OH)_x ETL, the power conversion efficiency of the ternary PM6:Y6:PC₇₁BM solar cell was increased from 16.1% to 17.8%. More importantly, such ZnO/C₆₀(OH)_x device maintained 80% of its original performance (T₈₀ lifetime) after being annealed at 65 °C for more than 6,973 hours in N₂. The T₈₀ lifetime at room temperature (25 °C) was estimated to exceed 34,635 hours. Detailed characterizations demonstrated that C₆₀(OH)_x can passivate the surface with regard to defects and effectively facilitated free radical scavenging. Overall, the ZnO/C₆₀(OH)_x device retained 91% of its initial PCE after continuous light soaking with a solar simulator at one-sun intensity for over 1,200 hours in N₂. For a relative humidity of 50% at 25 °C, the un-encapsulated ZnO/C₆₀(OH)_x device exhibited a T₈₀ exceeding 1,323 hours. The successful showcasing of this new interfacial stabilizer can spur additional research and momentum towards the advancement of future photovoltaic technologies.