Ultrafast optical spectroscopy of semiconducting nanowires and re-evaluation of photoluminescence intensity as an indicator of efficiency in perovskite solar cells

events hall

Prof. Faustino Martelli




The knowledge of the carrier dynamics in nanostructures is of fundamental importance for the development of (opto)electronic devices. This is true for semiconducting nanostructures as well as for plasmonic nanoparticles (NPs). In the first part of my presentation, I will review my recent activity on ultrafast spectroscopy in nanowires (NWs) and in NWs/NPs hybrid systems with emphasis on the hot-carrier dynamics in ZnSe, GaAsP and Si nanowires, with particular attention to the band-gap absorption bleaching dynamics and to its dependence on NW diameter. I will also show results on ZnSe-NWs/Ag-NPs and ZnSe-NWs/Au-NPs hybrids that allow the discussion of interaction mechanisms such as charge carrier transfer and Förster interaction.

In the second part of my talk, I will question the common claim that there is a direct relationship between the photoluminescence (PL) intensity of a perovskite solar cell (PSC) and its conversion performance. I will report on a systematic approach to the comparison of the conversion efficiency and the PL intensity of a cell in both open-circuit (OC) and short-circuit (SC) conditions and its application to multiple heterogeneous devices. I will show that the quenching of the photoluminescence observed in SC conditions is a good parameter to assess the device efficiency. The dependence of the PL quenching ratio between OC and SC on the cell efficiency is explained with a simple model that is also able to estimate the carrier extraction time of a device.

Host: Asst. Prof. Yonatan Calahorra


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