Multifunctional molecule of potassium nonafluoro-1-butanesulfonate for high-efficient perovskite solar cells

The rapid development of perovskite solar cell (PSC) makes it a typical representative of the third generation PV technology. The large-scale manufacturing of the device still faces many challenges, such as enhancing efficiency and improving stability. The core problem is the suppression of various defects and the adjustment of energy levels among components. In this report, a multifunctional molecule of potassium nonafluoro-1-butanesulfonate (KFBS) is introduced into SnO2 electron transport layer (ETL). Owing to the synergistic effect of potassium ion, sulfonic group and nonafluorobutane group in KFBS, the energy match between perovskite (PVK) and ETL is tuned, the PVK and ETL quality is improved, and the defects at interface, on grain boundaries and in bulk are passivated. Consequently, the power conversion efficiencies increase from 20.6% for pristine device to 23.21% for KFBS-modified device. Moreover, unpacked KFBS-modified device still maintains its initial efficiency of 90.5 % after storing at room temperature and relative humidity of 30 % in dark for 1000 h, showing an excellent environmental stability.