Exciton Diffusion Lengths and Dissociation Rates in CsPbBr3 Nanocrystal-Fullerene Composites: Layer-by-Layer versus Blend Structures

Yao, En-Ping; Bohn, Bernhard J.; Tong, Yu; Huang, He; Polavarapu, Lakshminarayana und Feldmann, Jochen (2019): Exciton Diffusion Lengths and Dissociation Rates in CsPbBr3 Nanocrystal-Fullerene Composites: Layer-by-Layer versus Blend Structures. In: Advanced Optical Materials, Bd. 7, Nr. 8, 1801776

Abstract

Solution-processable perovskite nanocrystals (NCs) are gaining increasing interest in the field of photovoltaics because of their enhanced stability compared to their thin-film counterparts. However, the charge transfer dynamics in perovskite NC based light-harvesting systems are not well understood. By applying femtosecond differential transmission (DT) spectroscopy the photoinduced charge transfer from inorganic perovskite CsPbBr3 NCs to the fullerene derivative phenyl-C61-butyric acid methyl ester (PCBM) is investigated for two fundamentally different architectures, namely layer-by-layer heterostructures and blend structures. By varying the thickness of the NC layer on top of the PCBM in the layer-by-layer heterostructure, an exciton diffusion length of 290 +/- 28 nm for CsPbBr3 NC is extracted. The diffusion process is followed by an ultrafast exciton dissociation (within 200 fs) at the CsPbBr3 NC/PCBM interface. In blend structures an overall faster charge transfer process is observed. Furthermore, photoconductivity measurements on a blend structure-based photodetector reveal an effective charge extraction from the active layer resulting in a high photosensitivity. DT measurements on this blend structure including adjacent electron- or hole-transport layers give insight into the extraction process and suggest a certain degree of phase segregation, which assists the charge collection.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Fakultätsübergreifende Einrichtungen: Center for NanoScience (CENS)
• Themengebiete: 500 Naturwissenschaften und Mathematik > 500 Naturwissenschaften ; 500 Naturwissenschaften und Mathematik > 530 Physik
• ISSN: 2195-1071
• Sprache: Englisch