Hybrid metal–polymer–semiconductor (MPS) diodes based on conducting polymers frequently exhibit inconsistent diode parameters when characterized using a single electrical technique, limiting the physical interpretation of charge transport. In this work, Al/PANI/n-Si heterojunction devices were investigated using a combined frequency-resolved experimental approach supported by numerical modeling. A spin-coated polyaniline (PANI) interlayer of ~ 75 nm thickness was employed, and the devices were characterized at room temperature by current–voltage (I–V), capacitance–voltage (C–V), conductance–voltage (G–V), and impedance spectroscopy measurements over the frequency range of 1 Hz–1 MHz. Thermionic-emission analysis of the I–V data yields an effective ideality factor of \(n \approx 2.83\) and a barrier height of \({\phi }_{B}\approx 0.67 eV\) and a saturation current of \({I}_{0}\approx 4.5 \times {10}^{-7}\boldsymbol{ }A\) , indicating pronounced non-ideal transport. Series resistance analysis indicated \(Rs \approx 3.2 \times 10^{5} \Omega\) , consistent with interface-limited conduction. A one-dimensional SCAPS-1D model incorporating experimentally constrained parameters reproduced the rectification and forward-bias behavior, while deviations in reverse leakage current and conductance were attributed to barrier inhomogeneity, trap-assisted transport, and finite contact resistance. Impedance spectroscopy revealed a single dominant relaxation process associated with the depletion capacitance at the PANI/n-Si interface, with capacitance values on the order of \(2 \times 10^{ - 9} F\) at 100 kHz, supported by semicircular Nyquist characteristics and equivalent-circuit analysis. These results demonstrate that conventional I–V analysis alone is insufficient to fully describe transport in polymer–Si MPS junctions, and that frequency-resolved characterization—complemented by predictive numerical modeling—provides a reliable framework for understanding and optimizing hybrid optoelectronic devices.
