The stability of perovskite solar cells (PSCs) has been greatly improved recently while very few studies focus on the long-term stability of the perovskite precursor solution. We report a novel route to greatly enhance the long-term stability of perovskite precursor solutions by incorporating a non-fullerene small molecule ITIC-Th. We found that the incorporation of ITIC-Th in the perovskite precursor solution can effectively suppress the unwanted yellow non-perovskite phase (δ-phase) commonly formed in the FAPbI3-based perovskite film made from a long-time aged precursor solution and consequently promote the formation of photoactive perovskite phase (α-phase). As a result, the devices fabricated from the aged precursor solution with ITIC-Th experience much less efficiency drop with the increase of the aging time of the precursor solution – from 19.20% (fresh) to 16.55% (39 days), compared with the devices made from conventional precursor solutions dropping from 18.07% (fresh) to 1.76% (39 days). Furthermore, the presence of ITIC-Th in the perovskite thin film gives rise to additional photocurrent as well as improved fill factor due to the well-matched energy levels, the passivation of defects and the complementary absorption spectra, suggesting a new route towards future high-efficiency solar cells – incorporating organic non-fullerene acceptors and halide perovskite materials into the same active layer.
Manuscript by Qin et al. was just accepted by Advanced Energy Materials, https://doi.org/10.1002/aenm.