B‐Site Co‐Alloying with Germanium Improves the Efficiency and Stability of All‐Inorganic Tin‐Based Perovskite Nanocrystal Solar Cells. Issue 49 (25th September 2020)

• Record Type: Journal Article
• Authors: Liu, Maning; Pasanen, Hannu; Ali‐Löytty, Harri; Hiltunen, Arto; Lahtonen, Kimmo; Qudsia, Syeda; Smått, Jan‐Henrik; Valden, Mika; Tkachenko, Nikolai V.; Vivo, Paola
• Is Part Of: Angewandte Chemie international edition. Volume 59:Issue 49(2020)
• Page Start: 22117
• Page End: 22125
• Publication Date: 2020-09-25
• Subjects: lead-free -- perovskite nanocrystals -- solar cells -- time-resolved photoluminescence -- ultrafast transient absorption spectroscopy; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202008724
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Colloidal lead‐free perovskite nanocrystals have recently received extensive attention because of their facile synthesis, the outstanding size‐tunable optoelectronic properties, and less or no toxicity in their commercial applications. Tin (Sn) has so far led to the most efficient lead‐free solar cells, yet showing highly unstable characteristics in ambient conditions. Here, we propose the synthesis of all‐inorganic mixture Sn‐Ge perovskite nanocrystals, demonstrating the role of Ge 2+ in stabilizing Sn 2+ cation while enhancing the optical and photophysical properties. The partial replacement of Sn atoms by Ge atoms in the nanostructures effectively fills the high density of Sn vacancies, reducing the surface traps and leading to a longer excitonic lifetime and increased photoluminescence quantum yield. The resultant Sn‐Ge nanocrystals‐based devices show the highest efficiency of 4.9 %, enhanced by nearly 60 % compared to that of pure Sn nanocrystals‐based devices. Abstract : CsSn0.6 Ge0.4 I3 nanocrystals have been synthesized for the first time by a B‐site co‐alloying strategy. The introduction of Ge effectively decreases the high density of intrinsic Sn defects, resulting in an extended excitonic lifetime and enhanced solar cell performance. The stability of the new nanocrystals also improves owing to the effective protection of Sn 2+ against oxidation.