Azide additive acting as a powerful locker for Li+ and TBP in spiro-OMeTAD toward highly efficient and stable perovskite solar cells. (1st June 2022) - Han, Yipeng
Abstract: The dopants of bis(trifluoromethane) sulfonimide lithium (Li-TFSI) and 4-tert-butylpyridine (TBP) in spiro-OMeTAD are significantly important for achieving highly efficient perovskite solar cells (PSCs). However, the volatility of TBP and hygroscopicity of Li-TFSI would accelerate the degradation process of PSCs. Herein, we demonstrated that the use of 1, 6-diazidohexane (N3) in spiro-OMeTAD can retard the evaporation of TBP and avoid aggregation/migration of lithium salt, leading to an enhanced conductivity/uniformity of spiro-OMeTAD layer. Additionally, N3 can minimize the TBP-PbI2 complex formation to improve the stability at perovskite/hole transport layer interface. As a result, we achieved a champion device with a power conversion efficiency (PCE) of 22.7% under AM 1.5G illumination. The unencapsulated devices can maintain good stability under illumination conditions. These findings provide a new strategy for the designs of extrinsic dopants in spiro-OMeTAD to further advance the stability of PSCs. Graphical Abstract: We synthesized 1, 6-diazidohexane (N3) compound as an effective dopant in HTL, which can stabilize Li-TFSI and TBP, and passivate perovskite surface defect, leading to an enhanced performance and stability of the devices. ga1 Highlights: 1, 6-diazidohexane (N3) serves as an effective dopant in spiro-OMeTAD/Li-TFSI/TBP layer. N3 can stabilize both Li-TFSI and TBP within the HTL, and can accelerate the oxidation process of spiro-OMeTAD. The doping of N3 confers enhanced charge carrier transport and better stability of the devices.