Route to Improving Photovoltaics Based on CdSe/CdSexTe1-x Type-II Heterojunction Nanorods: The Effect of Morphology and Cosensitization on Carrier Recombination and Transport

Sangheon Lee; Joseph C Flanagan; Byungho Lee; Taehyun Hwang; Jaewook Kim; Bumjin Gil; Moonsub Shim; Byungwoo Park

doi:10.1021/acsami.7b09745

Route to Improving Photovoltaics Based on CdSe/CdSe_xTe_1-x Type-II Heterojunction Nanorods: The Effect of Morphology and Cosensitization on Carrier Recombination and Transport

ACS Appl Mater Interfaces. 2017 Sep 20;9(37):31931-31939. doi: 10.1021/acsami.7b09745. Epub 2017 Sep 5.

Authors

Sangheon Lee¹, Joseph C Flanagan², Byungho Lee¹, Taehyun Hwang¹, Jaewook Kim¹, Bumjin Gil¹, Moonsub Shim², Byungwoo Park¹

Affiliations

¹ WCU Hybrid Materials Program, Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University , Seoul 08226, Korea.
² Department of Materials Science and Engineering and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.

PMID: 28850210
DOI: 10.1021/acsami.7b09745

Abstract

One-dimensionally elongated nanoparticles with type-II staggered band offset are of potential use as light-harvesting materials for photovoltaics, but only a limited attention has been given to elucidate the factors governing the cell performance obtainable from such materials. Herein, we describe a combined strategy to enhance charge collection from CdSe/CdSe_xTe_1-x type-II heterojunction nanorods (HNRs) utilized as light harvesters for sensitized solar cells. By integrating morphology- and composition-tuned type-II HNRs into solar cells, factors that yield interfaces favorable both for the electron injection into TiO₂ and hole transfer to electrolyte are examined. Furthermore, it is shown that a more efficient photovoltaic system results from cosensitization with CdS quantum dots (QDs) predeposited on a TiO₂ scaffold, which improves charge collection from HNRs. Electrochemical impedance spectroscopy (EIS) analysis suggests that such a synergistically enhanced system benefits from the decreased recombination within HNRs and facilitated charge transport through the cosensitized TiO₂ electrode, even with the activation of a recombination path presumably related to the photogenerated holes in CdS QDs.

Keywords: II−VI semiconductors; charge collection; nanorods; sensitized solar cells; type-II heterojunction.