A Bifunctional Carbazide Additive For Durable CsSnI 3 Perovskite Solar Cells

Inorganic CsSnI with low toxicity and a narrow bandgap is a promising photovoltaic material. However, the performance of CsSnI perovskite solar cells (PSCs) is much lower than that of Pb-based and hybrid Sn-based (e.g., CsPbX and CH(NH ) SnX ) PSCs, which may be attributed to its poor film-forming property and the deep traps induced by Sn . Here, a bifunctional additive carbazide (CBZ) is adapted to deposit a pinhole-free film and remove the deep traps via two-step annealing. The lone electrons of the NH and CO units in CBZ can coordinate with Sn to form a dense film with large grains during the phase transition at 80 °C. The decomposition of CBZ can reduce Sn to Sn during annealing at 150 °C to remove the deep traps. Compared with the control device (4.12%), the maximum efficiency of the CsSnI :CBZ PSC reaches 11.21%, which is the highest efficiency of CsSnI PSC reported to date. A certified efficiency of 10.90% is obtained by an independent photovoltaic testing laboratory. In addition, the unsealed CsSnI :CBZ devices maintain initial efficiencies of ≈100%, 90%, and 80% under an inert atmosphere (60 days), standard maximum power point tracking (650 h at 65 °C), and ambient air (100 h), respectively.