Ultrafast terahertz spectroscopy of novel perovskite photovoltaics

Lead Research Organisation: University of Warwick
Department Name: Physics

Abstract

Understanding the physics of the light-matter interaction in materials with the perovskite crystal structure is an extremely active and exciting topic at present. Inorganic-organic hybrid perovskites have provided an entirely new class of optoelectronic materials with excellent photovoltaic performance (over 22% solar power conversion efficiency), and have further potential for use in light emitters. However, the physics of what happens after light is absorbed in these compounds is poorly understood: some studies have concluded that free, mobile charges are created directly, while other work has reported the formation of excitons - bound electron-hole pairs. In this PhD project the student will investigate how free charges and excitons are created and subsequently move, using ultrafast terahertz spectroscopy. This is an advanced experimental method that probes the conductivity of materials as they respond to pulses of light with <1ps duration.

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509796/1 30/09/2016 29/09/2021
2108768 Studentship EP/N509796/1 30/09/2018 29/09/2022 Edward Butler-Caddle
EP/R513374/1 30/09/2018 29/09/2023
2108768 Studentship EP/R513374/1 30/09/2018 29/09/2022 Edward Butler-Caddle
 
Description Metal halide perovskite solar cells consist of a perovskite layer that absorbs light to excite electrons, and adjacent charge transport layers to transport these excited electrons.
This work has improved the understanding of this electron transfer behaviour for a selection of the best performing charge transport layers.

A new method has been demonstrated to improve the time range of optical pump terahertz probe spectroscopy (OPTP).
OPTP tracks the population and mobility of electrons in a material after they have been generated by a light pulse.
The time range of this technique is normally limited to a few nanoseconds, but the lifetime of electrons in metal halide perovskites and many other technologically important materials such as silicon is much longer than this.
This new method extends the time range to milliseconds in order to measure the full population dynamics in these materials.
Exploitation Route Understanding the behaviour of different charge transport layers is important for selecting the best layers to use in a perovskite photovoltaic cell.
Therefore, this will be useful to other academic researchers in this area and to researchers in industry that are working to commercialise this technology.

The demonstration of this new technique will be instructive to other researchers who will want to implement this technique to extend the time range of their optical pump terahertz probe experiment.
This method is implemented in the Warwick Centre for Ultrafast Spectroscopy (WCUS), which is a University of Warwick facility that can be used by both internal users (from the University of Warwick) and external users.
Sectors Electronics,Energy