Optimizing the structure of quantum dot Intermediate-band solar cells

Joint Event on 12^th International Conference and Exhibition on Materials Science and Chemistry & 30^th World Nano Conference

May 20-22, 2019 Zurich, Switzerland

Yoshitaka Okada

Research Center for Advanced Science & Technology, The University of Tokyo, Japan

Scientific Tracks Abstracts: J Material Sci Eng

Abstract :

Significant efforts have been devoted in order to demonstrate operation of quantum dot intermediate band solar cells (QD-IBSCs) [1]. The challenge for QD-IBSCs is to establish methods to fabricate high-density QDs arrays of low defect density with long carrier lifetimes. The areal density of QDs has direct influence on the generation and recombination processes via IB states since the total density of states of IB (NIB) is linked to the areal density Nareal as NIB = Nareal Ã? Nstacks / W, where Nstacks is the number of QD layer stacks and W is the width QD region, respectively. For this, we have shown that strain-compensated growth improves the QDs quality and characteristics of InAs/GaAs QDSCs with Nstacks up to 100 in self-organized heteroepitaxy by MBE. However, the average QD size prepared by such dry methods is still large and Nareal is low, typically limited to the range of 15-30 nm and 1011- 1012 cm-2, respectively. Furthermore, strain-induced bandgap widening of InAs QDs reduces the offset between the barriers, which results in an increased thermal escape of carriers out of QDs thereby reducing photocurrent production by 2-step photoabsorption (TSPA). In this work, optimization of QD-IBSC structure is studied for which PbS colloidal QDs of 4 nm in size were densely dispersed in a bulk CH3NH3PbBr3 perovskite matrix with a high energy bandgap of 2.4eV [2]. We focus on the TSPA characterization performed at room temperature.

Recent Publication

1. Y. Okada et al, Appl. Phys. Rev. 2, 021302 (2015). [2] H. Hosokawa et al, Nature Commun. (2019). DOI: 10.1038/s41467-018-07655-3.

Biography :

Yoshitaka Okada completed his PhD degree in electronic engineering from the University of Tokyo. He is currently a Professor in the Department of New Energy at the Research Center for Advanced Science and Technology (RCAST) of the University of Tokyo. His recent research interests include epitaxial film growth of low-dimensional quantum nanostructures as well as III-V-N dilute nitrides for applications to high efficient intermediate-band and hot carrier solar cells and multijunction solar cells. Dr. Okada is a member of the IEEE, Materials Research Society (MRS) and Japan Society of Applied Physics (JSAP). He has authored and co-authored over 200 refereed journal publications and over 230 international conference presentations..