Pyrolysis oil to power: Carbon nanomaterials as photosensitizers for high-performance Dye-Sensitized Solar Cells

Pyrolysis oil, a byproduct of biomass pyrolysis, has faced significant challenges due to its high acidity, complex composition, and low heating value, limiting its direct application. This study presents an innovative approach to valorize cornstalk-derived pyrolysis oil by transforming it into advanced carbon-based nanomaterials for Dye-Sensitized Solar cells (DSSCs). Through atmospheric distillation, pyrolysis oil was converted into bio-oil-derived char, featuring a hybrid structure of graphitic (sp²) and disordered (sp³) domains enriched with oxygen and nitrogen functionalities. This char served as a sustainable precursor for nanocarbon production (BCDs). Two types of carbon nanomaterials were synthesized: Carbon Quantum Dots via N, N-dimethylformamide (DMF) solvothermal treatment, and Carbon Nanodots via hydrogen peroxide (H₂O₂) oxidation. BCDs (DMF) exhibited a crystalline graphitic structure, green fluorescence, a high quantum yield (19.9 %), and a narrow band gap (2.2 eV). In contrast, BCDs (H₂O₂) displayed an amorphous structure, blue fluorescence, a lower quantum yield (9 %), and a wider band gap (2.8 eV). When applied as photosensitizers in DSSCs, BCDs (DMF) achieved a remarkable 59.2 % increase in power conversion efficiency (PCE) and a 47.7 % enhancement in short-circuit current density (Jsc) compared to BCDs(H₂O₂). The superior performance of BCDs (DMF) is attributed to their enhanced light absorption, lower recombination rates (k_eff), extended electron lifetimes (τ_n), faster electron transport times (τ_s), and more efficient charge transfer (R_ct). This study demonstrates a sustainable strategy for converting pyrolysis oil into functional nanomaterials, unlocking new opportunities for biomass-based clean energy applications.