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) (PE-DOT: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.