How can we dispose of heat in semiconductor nanocrystals?
Simon Boehme a
a Vrije University (VU) Amsterdam, De Boelelaan 1081, Amsterdam, Netherlands
nanoGe Perovskite Conferences
Proceedings of International Conference on Perovskite Thin Film Photovoltaics, Photonics and Optoelectronics (ABXPV18PEROPTO)
Perovskite Photonics and Optoelectronics (PEROPTO18). 1st March
Rennes, France, 2018 February 27th - March 1st
Organizers: Jacky Even and Sam Stranks
Poster, Simon Boehme, 078
Publication date: 11th December 2017

Energy conversion processes in semiconductor nanocrystals typically occur with non-unity yields. Much of the losses involve the generation of heat, for example via electronic relaxation after photoexcitation. Surprisingly, a central question remains unanswered: how can we dispose of (or maintain) this heat? The present lack of an answer to this question hinders the development of more efficient and stable optoelectronic (or thermoelectric) devices.

In this talk, I will discuss the possibility and implications of heat dissipation from a nanocrystal core to its environment, i.e. ligands and surrounding matrix (e.g. solvent molecules). I address the current challenge of correlating electronic and nuclear excitations by probing them simultaneously, using a combination of transient absorption and femtosecond stimulated Raman spectroscopy, respectively. This enables us to monitor both electronic the thermal processes in real-time, in a single experiment. Such an approach, while currently pioneering the fields of optogenetics and protein folding, has not yet been applied to the field of semiconductor nanocrystals.

Specifically, I will report on (sub-)picosecond thermal processes in CsPbBr3 nanocrystals and compare them to more traditional systems such as prototypical CdSe and PbS nanocrystals. These systems differ in a wide range of heat-related processes, from charge-carrier cooling rates to melting points of the crystalline core. In this talk, I will stimulate a critical discussion on how chemical insight can help understand photophysical processes, and vice versa. As such, we take the first steps towards a better control of heat dissipation in devices such as LEDs, solar cells, or thermoelectrics.

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