Carrier Lifetimes of >1 ms in Sn-Pb Perovskites Enable Efficient All-Perovskite Tandem Solar Cells

May 3, 2019

The addition of guanidinium thiocyanate (GuaSCN) resulted in marked improvements in the structural and optoelectronic properties of Sn-Pb mixed, low-band gap (~1.25- eV) perovskite films.

Scientific Achievement

We demonstrate for the first time extraordinarily long carrier lifetime (>1 µs) and diffusion length (~2.5 µm) in tin-lead (Sn-Pb) mixed low-bandgap (~1.25-eV) perovskite films achieved via novel solution chemistry based on GuaSCN.

Significance and Impact

GuaSCN additive induces formation of 2D barrier on grain surface, which suppresses oxidation of Sn2+, reduces defect density, and enables our demonstration of >20%-efficient Sn-Pb mixed perovskite solar cells and 25%-efficient all-perovskite tandem cells.

Research Details

  • Solution processing to prepare low-bandgap (1.25-eV) (FASnI3)0.6(MAPbI3)0.4 perovskite thin films
  • GuaSCN additive to tune perovskite film formation and optoelectronic properties
  • Detailed spectroscopic and electrical measurements to understand carrier dynamics and defect properties

DOI: 10.1126/science.aav7911

Related People

Matthew Beard
National Renewable Energy Laboratory

Joseph J. Berry
National Renewable Energy Laboratory

Yanfa Yan
University of Toledo

Kai Zhu
National Renewable Energy Laboratory

Comparison of carrier lifetime (transient photoluminescence) and surface recombination (transient reflection) of Sn-Pb low-bandgap perovskite thin films prepared (A, C) without and (B, D) with the use of 7% GuaSCN modifier. Carrier lifetime: 139 ns (0% GuaSCN) and 1,232 ns (7% GuaSCN); surface recombination velocity: 1.3×103 cm/s (0% GuaSCN) and 1.0×102 cm/s (7% GuaSCN).