<p>This study investigates the enhancement of optoelectronic device performance of P3HT:PCBM in active layer with the different nanocarbon materials as electron transport layer (ETL). The fullerene (C₆₀), SWCNTs (single wall carbon nano tube), MWCNTs (multi-wall carbon nano tube), and reduced graphene oxide (rGO) are the different carbon-based nanomaterials used as ETL. Surface analysis by FESEM showed that rGO films possessed a smoother morphology with minimal aggregation compared to other nanocarbon materials. The absorption spectra of the composites, as well as those of the ETLs, indicate the smooth and uniformity for rGO flakes. Electrical analysis demonstrated rectifying <i>I</i>–<i>V</i> characteristics, with ideality factors of 4.4 (D1), 4.1 (D2), 3.5 (D3), and 2.2 (D4). In case of C₆₀ and CNTs, the reverse saturation current increased as 1.75 × 10⁻⁷, 2.4 × 10⁻⁷, and 2.2 × 10⁻⁷ compared to rGO 1.35 × 10⁻⁸. The rGO-based device (D4) exhibited superior optoelectronic response, achieving a higher value of responsivity of 5.12&#xa0;mA/W and detectivity of 3.2 × 10⁹ Jones at − 2&#xa0;V, in contrast to other ETLs nanomaterials. Electrochemical impedance spectroscopy supported these findings, showing a high recombination resistance (9.28 kΩ) and long electron lifetime (9.37 × 10⁻³&#xa0;s) for D4, indicating reduced recombination and efficient charge transport. These results demonstrate that the rGO-based device is the most effective ETL for enhancing structural, optical, and electrical characteristics of P3HT:PCBM composites. rGO can be treated as the strong candidate for next-generation optoelectronic applications.</p>