Enhanced Power Conversion Efficiency of Polymer Solar Cells Through Optimized Bilayer Tuning of PCBM and P3HT with Electron Blocking Layers PEDOT:PSS and Polyaniline

This study investigates the optimization of bilayer polymer solar cells (PSCs) using Poly(3-hexylthiophene) (P3HT) as the donor and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the acceptor. The active layers were prepared by spin coating at an optimized speed of 2000 rpm, followed by post-production annealing at 100°C. The electron-blocking layer (EBL) of PEDOT:PSS or polyaniline (PANI) was deposited under controlled conditions and annealed at 120°C for 15 minutes. Structural and morphological properties of the thin films were analyzed using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). Optical and electrical characteristics were evaluated using UV-Vis spectroscopy and Keithley electrometer under illumination. The results indicate that optimizing the thickness of the P3HT:PCBM bilayer significantly enhances the power conversion efficiency (PCE) by improving exciton dissociation and charge transport. SEM analysis revealed uniform film morphology, while XRD patterns showed distinct crystalline features, particularly for the P3HT layer. FT-IR spectra confirmed the successful deposition of the layers with characteristic functional groups. Electrical performance analysis demonstrated that annealing and bilayer thickness optimization reduced recombination losses, leading to higher short-circuit current density (Jsc) and open-circuit voltage (Voc). These findings emphasize the importance of layer thickness, morphology, and thermal processing in achieving efficient bilayer PSCs.