The Impact of Multifunctional Ambipolar Polymer Integration on the Performance and Stability of Perovskite Solar Cells

Effective passivation of grain boundaries in perovskite solar cells is essential for achieving high device performance and stability. However, traditional polymer-based passivation strategies can introduce challenges, including increased series resistance, disruption of charge transport, and insufficient passivation coverage. In this study, a novel approach is proposed that integrates a multifunctional ambipolar polymer into perovskite solar cells to address these issues. The ambipolar polymer is successfully incorporated into both the perovskite film and the hole transport layer (HTL), enabling comprehensive restoration of defect sites within the perovskite active layer. Moreover, this approach yields additional advantages for perovskite devices, such as enabling bidirectional charge transport, limiting pinhole formation at the HTL, reducing lithium-ion migration from the HTL to the perovskite, and minimizing both the band offset and surface energy difference between the perovskite film and HTL interface. With these benefits, the ambipolar polymer integrated device achieves a power conversion efficiency (PCE) of 24.0%. Remarkably, it also exhibits enhanced long-term stability, preserving 92% of its initial PCE after 2000 h under ambient conditions, and 80% of its initial PCE after 432 h under harsh conditions (at 85 °C and 85 ± 5% RH).