Polyelectrolyte-Doped SnO_2 as a Tunable Electron Transport Layer for High-Efficiency and Stable Perovskite Solar Cells

摘要

The charge transport layer is crucial to the performance and stability of theperovskite solar cells (PSCs). Compared with other conventional metal oxideelectron transport materials, SnO_2 has a deeper conduction band and higherelectron mobility, and can efficiently serve as an electron transport layer tofacilitate charge extraction and transfer. Herein, an optimized low-temperaturesolution-processed SnO_2 electron transport layer is achieved by doping polyethyleniminepolyelectrolyte into SnO_2 for the first time in the PSCs. It is foundthat the performance of all aspects of the doped SnO_2 film is improved over thatof the pristine SnO_2 film. The better energy level alignment, larger built-in field,enhanced electron transfer/extraction, and reduced charge recombination allcontribute to the improved device performance. Finally, a PSC with a powerconversion efficiency of 20.61% is successfully prepared under low temperaturebelow 150℃. Moreover, the stability of the doped SnO_2-based device is alsogreatly improved.