A sulfur-rich small molecule as a bifunctional interfacial layer for stable perovskite solar cells with efficiencies exceeding 22%.

Remarkable progress has been made in perovskite solar cells (PSCs) recently. However, the defects present in the perovskite layer act as non-radiative recombination centers to decrease the stability and restrict the further performance improvement of the device. We report herein a sulfur-rich two-dimensional small molecule, SMe-TATPyr, as a bifunctional layer to efficiently passivate the surface defects of perovskite and facilitate the hole transfer at the perovskite/spiro-OMeTAD interface. X-ray photoelectron spectroscopy analyses show that the sulfur atoms of SMe-TATPyr can passivate the uncoordinated Pb²⁺ defects and suppress the Pb⁰ defect formation as Lewis bases. As a result, the power conversion efficiency of PSCs is distinctly increased from 20.4% to 22.3%. Moreover, this simple interfacial modification could effectively enhance the stability of unencapsulated PSCs to retain 95% of the initial efficiency after storage for 1500 h at ambient conditions, in contrast to 70% efficiency retention of the device without SMe-TATPyr under the same conditions. ga1 A sulfur-rich two-dimensional small molecule, SMe-TATPyr, has been used as a bifunctional interlayer to efficiently passivate the surface defects of perovskite and facilitate the hole transfer at the perovskite/spiro-OMeTAD interface. The SMe-TATPyr-treated perovskite solar cells demonstrate a remarkable efficiency of 22.3%, along with 95% retention of the initial efficiency under storage for 1500 h at ambient conditions. • A sulfur-rich small molecule is designed as a bifunctional reagent for interfacial defect passivation and hole transfer. • The use of the interfacial layer leads to the efficiency enhancement from 20.4% to 22.3%. • The effect of interfacial defect passivation is fully supported by different physical measurements. [ABSTRACT FROM AUTHOR]