Amide-Catalyzed Phase-Selective Crystallization Reduces Defect Density in Wide-Bandgap Perovskites

Junghwan Kim, Makhsud I. Saidaminov, Hairen Tan, Yicheng Zhao, Younghoon Kim, Jongmin Choi, Jea Woong Jo, James Fan, Rafael Quintero-Bermudez, Zhenyu Yang, Li Na Quan, Mingyang Wei, Oleksandr Voznyy*, Edward H. Sargent

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

83 Scopus citations


Wide-bandgap (WBG) formamidinium–cesium (FA-Cs) lead iodide–bromide mixed perovskites are promising materials for front cells well-matched with crystalline silicon to form tandem solar cells. They offer avenues to augment the performance of widely deployed commercial solar cells. However, phase instability, high open-circuit voltage (Voc) deficit, and large hysteresis limit this otherwise promising technology. Here, by controlling the crystallization of FA-Cs WBG perovskite with the aid of a formamide cosolvent, light-induced phase segregation and hysteresis in perovskite solar cells are suppressed. The highly polar solvent additive formamide induces direct formation of the black perovskite phase, bypassing the yellow phases, thereby reducing the density of defects in films. As a result, the optimized WBG perovskite solar cells (PSCs) (Eg ≈ 1.75 eV) exhibit a high Voc of 1.23 V, reduced hysteresis, and a power conversion efficiency (PCE) of 17.8%. A PCE of 15.2% on 1.1 cm2 solar cells, the highest among the reported efficiencies for large-area PSCs having this bandgap is also demonstrated. These perovskites show excellent phase stability and thermal stability, as well as long-term air stability. They maintain ≈95% of their initial PCE after 1300 h of storage in dry air without encapsulation.

Original languageEnglish (US)
Article number1706275
JournalAdvanced Materials
Issue number13
StatePublished - Mar 27 2018


  • amides
  • defects
  • perovskite solar cells
  • wide-bandgap perovskites

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering


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