(Invited) High Performance Carbon Nanotube –Laminated Perovskite Solar Cells
Authors: Shawky Ahmed , Jeon Il , Xiang Rong , Inoue Taiki , Matsuo Yutaka , Maruyama Shigeo 
Published: February 2020

Recently, perovskite solar cells (PSCs) have got much attention since the big jump of the power conversion efficiency (PCE) from about 3.9% [1] to 23.3% [2] in less than a decade that is comparable to the developed Si and CIGS-based counterparts in more than 40 years. Accordingly, tremendous efforts have been devoted on increasing durability of the produced devices at low cost. PSC commonly invented by sandwiching the perovskite layers between two charge selective transport layers. Then, the two conducting electrodes are placed outside of charge selective layers, one is facing the light usually transparent conducting oxide, and the other is a noble metal like gold or silver. The metal electrode typically prepared by thermal evaporation at high vacuum level that’s substantially increase the cost as well for the cost of noble metal. Moreover, these metals either react with the PSC components or migrate into the device at environmental temperature and operational conditions that is subsequently reduces the overall performance and stability [3].
Single-walled carbon nanotubes (SWCNTs) displayed superb physical, properties in terms of conductivity, light absorption, thermal, mechanical, and chemical ones. SWCNTs could be incorporated into the PSC system [4]. SWCNTs is a favorable electrode material, owing to its abundance, hydrophobicity, and mechanical robustness [5]. The application of SWCNT as the top electrode expressively enhances the stability of PSCs by removing the ion migration, and considerably reduces the fabrication cost as it can be easily deposited onto devices by a simple mechanical transfer [6]. We recently showed that the trifillic acid-treated SWCNTs can have a great applicability with 2D/3D FACsPbI3 system reaching PCE of 17.6% with enhanced stability [7]. The conductivity of SWCNT film could be increased as the work function is tuned by using a vapor-assisted doping of trifluoromethanesulfonic acid (TFMS).
We extend this work on the MAPbI3 system showing better performance. In this presentation, we will present our latest results on doping of SWCNT electrodes with diluted solution of TFMS having a new record of PCE for the SWCNT-based PSCs. Our devices showed higher PCE of more than 18 % with a J
SC of 22.67 mA cm-2, V
OC of 1.104 V, and FF of 0.724 through the optimization of hole transport layer concentration as shown in figure 1. Additionally, we will show the possibility of introducing our new 1D heterostructures by wrapping of various SWCNT with BN and TMD layers using chemical vapor deposition into the solar cells and devices field. These SWCNT-based heterostructures are expected to have a broad interest and impact in fabricating BN-protected or gated SWNT devices and building more sophisticated 1D material systems [8]. These new structures are expected to give extra functionality, durability, and great applicability in electronic, optoelectronic, and energy devices.
References:
[1] A. Kojima et al., J. Am. Chem. Soc., (2009), 6050.
[2] NREL’s best research efficiency chart., (2018).
[3] K. Domanski et al., ACS Nano, 10 (2016), 6306.
[4] I. Jeon et al., Topics Curr. Chem., (2018), 376:4.
[5] I. Jeon et al., Adv. Energy Mater., (2018) online [DOI:10.1002/aenm.201801312].
[6] I. Jeon et. al., J. Phys. Chem. C, (2017), 121, 25743.
[7] J.-W. Lee et. al. Nano Lett., (2018), ASAP [DOI: 10.1021/acs.nanolett.8b04190].
[8] R. Xiang et al., (2018), submitted. [Cite: https://arxiv.org/abs/1807.06154].

Figure 1