Single walled carbon nanotube incorporated Titanium dioxide and Poly(3-hexylthiophene) as electron and hole transport materials for perovskite solar cells

doi:10.1016/j.matlet.2020.128174

Materials Letters

Volume 276, 1 October 2020, 128174

https://doi.org/10.1016/j.matlet.2020.128174 Get rights and content

Highlights

•
CNT either at the TiO₂/perovskite interface or in HTM strongly influences the efficiency.
•
CNT at the TiO₂/perovskite enhances the efficiency of the solar cells up to 30%.
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CNT both at TiO₂/perovskite interface and in HTM enhances the efficiency up to 50%.

Abstract

This study focuses on incorporating single wall carbon nanotubes (CNTs) in both electron conducting porous Titanium dioxide (TiO₂) and the hole conducting Poly(3-hexylthiophene) (P3HT) layers in order to enhance the performance of perovskite solar cells. The CNT was incorporated at TiO₂/CH₃NH₃PbI_xCl_3-x interface by dip coating TiO₂ electrodes with CNT solution prior to deposition of CH₃NH₃PbI_xCl_3-x and by blending with P3HT, respectively. Raman spectra and Atomic Force Microscopic (AFM) images confirmed the presence of CNT in TiO₂ electrodes and in P3HT, respectively. Optimized devices with the CNT show overall power conversion efficiencies (PCE) over 14%, under 100 mW/cm² illumination with Air Mass 1.5 filter, which is 50% higher than that of the control device which is not having CNT. The enhancement is predominantly due to increase in short circuit current density (J_SC) and fill factor, which resulted from surface passivation at the interface by CNT.

Graphical abstract

Introduction

Perovskite solar cells (PSCs) have become a research hot-spot due to its low-cost fabrication techniques together with high efficiency [1], [2]. It has a perovskite layer sandwiched between an electron and hole transporting layer with transparent conducting oxide and gold thin films as the electrodes. Both electron and hole transporting layers play a vital role in charge transport in these PSCs. Optimizing the charge transport properties in these transporting layers is one of the strategies to improve the PCE of PSCs [3]. In recent years, a few works have been focused on the application of CNT in PSCs due to their outstanding electrical, optical, mechanical, and structural properties [4].

In conventional PSCs, TiO₂ is regarded as one of the best electron extracting and transporting material. It was reported that the charge transfer at the interface was significantly improved after introducing CNT in Electron Transporting Materials (ETM), which effectively increases the electron collection [5]. P3HT is one of the best studied Hole Transporting Material (HTMs) for PSCs. However, the hole-mobility is the key challenge in enhancing the efficiency of PSCs.

In this study, we focus on enhancing the performance of PSCs by utilizing CNTs (i) at TiO₂/perovskite interface, (ii) in P3HT HTM, and (iii) in both TiO₂/perovskite interface and P3HT HTM, and to the best of our knowledge this is the first study reporting all these effects together in PSCs.

Section snippets

Materials and methods

The device fabrication and characterization techniques of PSCs with and without CNT can be found in the supporting information (SI) and refs. [6], [7].

Results and discussion

In this study, CNT bundles (IsoNanotubes S-99, NanoIntegris, Canada) which are predominantly p-type semiconductors after sonication [8], [9] were incorporated at the TiO₂/CH₃NH₃PbI_xCl_3-x interface and/or P3HT. Fig. 1(a) shows the Raman spectra of bare TiO₂ and CNT dip-coated TiO₂ electrodes, recorded using Raman spectrometer (EZRAMAN, Model: 5B1S-162) with a 532 nm laser. The peaks obtained at the wavenumbers of 1124 and 1407 cm⁻¹ corresponding to D-band and G-band, respectively confirm the

Conclusion

In this work, the impact of the incorporation of CNT at TiO₂/perovskite interface, in P3HT, and in both TiO₂/perovskite interface and in P3HT has been studied. The best performance was achieved when CNT was incorporated in both TiO₂/perovskite interface and P3HT, and above 50% enhancement in PCE was recorded compared to control device fabricated without incorporating CNT. Notably, all CNT incorporated PSCs exhibited higher FF, and it can be explained by the passivation of charge recombination.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

Authors acknowledge CBERC (LKA-3182-HRNCET), HRNCET (NORPART/2016/10237) projects and Ministry of Science Technology and Research, Sri Lanka for providing financial support.

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Single walled carbon nanotube incorporated Titanium dioxide and Poly(3-hexylthiophene) as electron and hole transport materials for perovskite solar cells

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials and methods

Results and discussion

Conclusion

Declaration of Competing Interest

Acknowledgement

J. Power Sources

Mater. Lett.

Data Br.

Biosens. Bioelectron.

IScience

Materials (Basel)

Nature