Doping and Switchable Photovoltaic Effect in Lead‐Free Perovskites Enabled by Metal Cation Transmutation

• Published in: Advanced materials (Weinheim) Vol. 30; no. 34; pp. e1802080 - n/a
• Main Authors: Harikesh, Padinhare Cholakkal, Wu, Bo, Ghosh, Biplab, John, Rohit Abraham, Lie, Stener, Thirumal, Krishnamoorthy, Wong, Lydia Helena, Sum, Tze Chien, Mhaisalkar, Subodh, Mathews, Nripan
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.08.2018
• Subjects: 2D layered perovskite; Absorptivity; Antimony; Cations; Deoxidizing; doping; Heavy metals; Lead; lead‐free perovskite; Materials science; Metal ions; Perovskites; Photovoltaic cells; Photovoltaic effect; Solar cells; switchable photovoltaics; Tin; Transmutation; doping; lead-free perovskite; antimony; 2D layered perovskite; switchable photovoltaics
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.201802080

Creating defect tolerant lead‐free halide perovskites is the major challenge for development of high‐performance photovoltaics with nontoxic absorbers. Few compounds of Sn, Sb, or Bi possess ns2 electronic configuration similar to lead, but their poor photovoltaic performances inspire us to evaluate other factors influencing defect tolerance properties. The effect of heavy metal cation (Bi) transmutation and ionic migration on the defects and carrier properties in a 2D layered perovskite (NH4)3(Sb(1−x)Bix)2I9 system is investigated. It is shown, for the first time, the possibility of engineering the carriers in halide perovskites via metal cation transmutation to successfully form intrinsic p‐ and n‐type materials. It is also shown that this material possesses a direct–indirect bandgap enabling high absorption coefficient, extended carrier lifetimes >100 ns, and low trap densities similar to lead halide perovskites. This study also demonstrates the possibility of electrical poling to induce switchable photovoltaic effect without additional electron and hole transport layers. The effect of heavy metal cation (Bi) transmutation and ionic migration on the defects and carrier properties in a 2D layered perovskite (NH4)3(Sb(1−x) Bix)2I9 system is investigated. This transmutation enables the formation of intrinsic p‐ and n‐type materials with a direct–indirect bandgap, extended carrier lifetimes >100 ns and low trap densities similar to lead halide perovskites. It is also shown that this material exhibits a switchable photovoltaic effect without additional electron and hole extraction layers.