Sustainable materials for organic photovoltaic devices towards transient electronics in digital agriculture

With the growing demand for sustainable energy solutions, particularly for energy supply in transient sensor systems, this study focused on environmentally friendly materials in organic photovoltaics (OPV) and their key photovoltaic parameters. The application of regenerated cellulose (RC), gelatin and propylene glycol (PGG) as biodegradable alternatives to fossil-based PET film substrates and soil-compatible carbon paste (SCP) as a replacement for evaporated metal electrodes was assessed for electronics. The investigated aspects included the current–voltage characteristics, leakage current, and cell efficiency under LED illumination at 1000 lx, relevant for IoT applications. Both the commercial and newly developed OPV components were then analyzed in terms of their microstructure, water solubility, and layer integration. Results showed that RC can serve as a promising alternative substrate for OPV, achieving a power conversion efficiency (PCE) of 15.88%, and the electrical properties of OPVs incorporating the developed SCP were significantly higher than those of the OPVs that used the commercial carbon paste (CP) electrode. SEM analysis confirmed good adhesion and uniformity between layers, supporting the mechanical integrity of the device. Despite the high leakage currents in devices with printed SCP electrodes, further optimization can improve the overall device performance. The water solubility and environmental impact of the OPV materials were assessed through conductivity and pH measurements over six months, revealing no significant changes in soil quality, with pH levels remaining within the plant-safe range of 6.0 to 7.5. The findings of this study demonstrate the performance of OPVs utilizing soil-compatible materials for transient electronics, towards fulfilling the requirements of energy autonomous sensing in digital agriculture applications while maintaining ecological integrity.