Multiwalled Carbon Nanotubes as Hole Collectors in Inverted Perovskite Solar Cells

Carbon nanotubes (CNTs) are known for their unique photoelectric and mechanical properties, but their manufacturing process often requires high thermal energy. This study presents a simple solvothermal method to produce multiwalled carbon nanotubes (MWCNTs) from acetyl ferrocene at a low temperature of 250 °C. The synthesized MWCNTs were fully characterized and elucidated through X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The MWCNTs were then incorporated into poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) at different weight ratios (2.5, 5, and 10%) as a hole transporter in perovskite solar cells. The results of UV–vis spectroscopy showed that MWCNTs/PEDOT:PSS did not affect the photon transmission to the perovskite layer. Photoluminescent analysis for PEDOT:PSS and optimal MWCNTs significantly reduced light emission by 93.3% for 5% MWCNTs in PEDOT:PSS. The device with the optimized 5% MWCNTs/PEDOT:PSS hole collector achieved an efficiency of 18.09%, compared to 16.51% for pristine PEDOT:PSS. This work demonstrates a promising approach for enhancing the efficiency of inverted planar perovskite-based devices through the use of MWCNTs prepared at low temperatures using a simple solution process.