Suppression of PbI2 decomposition with Lewis base semicarbazide hydrochloride for photostable and efficient perovskite solar cells

Introducing excessive PbI 2 in perovskite is widely used to fabricate high performance perovskite solar cells (PSCs) via two-step spin coating , whereas the photoinduced decomposition of excessive PbI 2 may induce perovskite photodegradation for long-term illumination. In this work, a Lewis base semicarbazide hydrochloride (SH) is introduced in the first-step PbI 2 film, which can anchor strongly PbI 2 at the grain boundaries of perovskite, suppressing its photoinduced decomposition to Pb 0 and I 2 , and consequently enhancing the long-term photostability of PSCs. In addition, it is verified that SH can also coordinate with the uncoordinated Pb 2+ in perovskite, and thus stabilize [PbX 6 ] 4- octahedral to inhibit photoinduced ion migration. Therefore, the optimized PSC exhibits not only an improved power conversion efficiency (PCE) of 21.88%, but also an enhanced photostability with 82.8% of its initial PCE under 500 h continuous AM 1.5G illumination. This work provides a new strategy to suppress PbI 2 photoinduced decomposition and perovskite photodegradation for the realization of photostable and efficient PSCs.