Perovskite photocatalysis: realizing long-lived charge-separated states at the interface of CsPbBr3 nanocrystals and functionalized ferrocene molecules

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2022-10, Vol.10 (39), p.21112-21123
• Main Authors: Singh, Siddharth, Mittal, Diksha, Gurunarayanan, Vinithra, Sahu, Ankita, Ramapanicker, Ramesh, Vishal Govind Rao
• Format: Article
• Language: English
• Subjects: Absorption spectra; Amino acids; Bleaches; Carboxylic acids; Carrier recombination; Cesium; Charge efficiency; Crystals; Current carriers; Dipoles; Energy conversion efficiency; Hydrophobicity; Lead compounds; Metal halides; Nanocrystals; Perovskites; Photocatalysis; Photovoltaic cells; Recombination; Solar cells; System effectiveness
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d2ta05692e

Cesium lead halide (CsPbX3) perovskites, having stood out for solar cell applications, are now garnering attention in the field of photocatalysis as well. With a fundamental challenge in photocatalysis of timely charge carrier extraction before recombination, incorporating ferrocene (Fc)-based functionalities can offer remarkable charge extraction efficiency in lead halide perovskites, given a recent 25% power conversion efficiency in a solar cell developed with a similar approach. Here, we have covalently linked Fc with amino acid residues to design three molecular redox relays differing in the ratio of –COOH to Fc units and employed them to probe the hole transfer dynamics in CsPbBr3 perovskite nanocrystals (NCs) for photocatalytic applications. With Fc forming a part of the hydrophobic tail, the presence of the polar carboxylic acid (–COOH) headgroup endowed the molecule with a surfactant-type nature so that it could bind to the CsPbBr3 NCs' surface in colloidal solution. Interestingly, the enhanced binding in all three cases, as evident by the XPS peak shift, led to the formation of a long-lived charge-separated state when a dipole was created between the electrons in CsPbBr3 and holes in surface-bound Fc derivatives. This was evident in the transient absorption spectra when an unusually sustained bleach of the CsPbBr3 excitonic peak was observed in the presence of Fc derivatives. Such prolonged existence of the charge-separated state undoubtedly reflects upon the utility of molecular systems as cost-effective as Fc derivatives in perovskite NCs to carry out photocatalytic reactions where timely extraction of charge carriers is always a challenge to overcome.