Comparison of performance and optoelectronic processes in ZnO and TiO 2 nanorod array-based hybrid solar cells

Fan Wu, Qiquan Qiao, Behzad Bahrami, Ke Chen, Rajesh Pathak, Sally Mabrouk, Yanhua Tong, Xiaoyi Li, Tiansheng Zhang, Ronghua Jian

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

The reported efficiencies of pristine ZnO nanorod array (NRA)-based polymer-inorganic hybrid solar cells (HSCs) are normally lower than those of their pristine TiO 2 NRA-based counterparts. This difference typically results from the lower short-circuit current density (J sc ) of the ZnO NRA device. This paper presents a comparative study of pristine ZnO and TiO 2 NRA-based HSCs. We investigate the morphological structure (length, diameter, number density, area of nanorod laterals), photovoltaic performance (current density-voltage J–V, external quantum efficiency EQE), and optoelectronic processes related to electron transfer (electron mobility μ e , electron diffusion length L D , electron lifetime τ e and electron transit time τ t related electron collecting efficiency η cc , electron injection η inj , surface potential SP, photoluminescence PL, bound charge pairs BCP) in HSCs, with ZnO and TiO 2 NRA as electron acceptor. Our comparative investigations reveal that the factors relating to the interface area, μ e , L D , and η cc are not the key factors responsible for the difference in the value of J sc in ZnO and TiO 2 NRA-based HSCs with the same device structure. In fact, the crucial step for a lower J sc in ZnO NRA-based HSCs than in TiO 2 NRA-based HSCs is attributed to the less efficient transfer of photo-generated electrons at the charge separation interface in ZnO NRA-based HSCs. Dynamic characterizations indicate that the transfer of interfacial photo-generated electrons in TiO 2 NRA-based HSCs is more efficient than ZnO NRA-based HSCs, and is confirmed by Kelvin probe force microscopy (KPFM) and PL studies. The reason for the better interface charge transfer property in MEH-PPV/TiO 2 NRA than that of in MEH-PPV/ZnO NRA is further investigated by Marcus model, we find that more trapped BCP states are generated in the ZnO NRA based HSCs, which resulting in lower interfacial electron injection efficiency from polymer to ZnO NRA.

Original languageEnglish (US)
Pages (from-to)124-132
Number of pages9
JournalApplied Surface Science
Volume456
DOIs
StatePublished - Oct 31 2018
Externally publishedYes

Keywords

  • Hybrid semiconductor
  • Nanorod array
  • Optoelectronic processes
  • Solar cells

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Physics and Astronomy(all)
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

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