Guanine-assisted defect passivation for high-efficiency n-i-p planar perovskite solar cells

Perovskite film is a polycrystalline film, coupled with its own soft lattice ionic material characteristics, and the rapid crystallization during the preparation process will inevitably produce a large number of defects within the film and at the interface. However, passivation using Lewis base and Lewis acid compounds can effectively suppress carrier recombination caused by these defects, greatly enhancing the overall performance of perovskite solar cells (PSCs). In order to achieve a better passivation effect, we employed guanine, a purine derivative, as a Lewis base by incorporation, which not only inhibits water degradation and ion migration and reduces trap defects by coordinating with uncoordinated ions, but also improves carrier transport by less non-radiative recombination. The guanine-modified devices exhibited significant enhancements compared to the original devices, with the corresponding devices exhibiting efficiencies of more than 23% (0.04 cm2). The PSCs of the unencapsulated guanine-modified devices, storage in air at 25 ± 5 °C and 5–10% RH for 1200 h, retained 85% of the initial power conversion efficiency (PCE), which is much higher than that of the untreated devices, yielding satisfactory stability.