Organic photovoltaics (OPVs) are attractive candidates for sustainable energy conversion due to their flexibility, lowcost processing, and compatibility with large-area fabrication. However, their efficiency is hindered by interfacial defects and vertical phase separation in the active layer, which induce charge imbalance and recombination losses. This work presents an interfacial engineering approach to overcome these limitations in P3HT:PC₇₀BM-based OPVs. Two key strategies were employed: (i) reducing the post-deposition annealing time of the active layer to suppress PC₇₀BM accumulation at the bottom electrode, and (ii) using a DCB:DCM mixed solvent system to regulate solvent evaporation, thereby promoting uniform film formation during PC₇₀BM overlay deposition. Devices fabricated with these optimizations exhibited notable enhancements, achieving short-circuit current density up to 15.83 mA/cm² and a 58.1% increase in power conversion efficiency compared to control devices. X-ray photoelectron spectroscopy confirmed reduced surface aggregation of PC₇₀BM, while X-ray diffraction indicated improved P3HT crystallinity and molecular ordering. These results highlight the critical role of interfacial and morphological control in enhancing charge separation and transport, offering a practical route toward efficient, reproducible, and stable OPVs.

The printed and bifacial organic photovoltaics (OPVs) using a semi-transparent electrode structure to enhance light management were investigated. To optimize energy-band alignment for bifacial device structure, a cathode interlayer of ZnO nanoparticles with a low work function of 3.9 eV combined with a polyethyleneimine (PEI) layer was employed. Photon distribution simulations revealed the influence of structural parameters on device conductivity, light absorption, and surface morphology. The dispensing strength, adjusted via applied voltage during printing, significantly impacted device performance. At 13 V and 17 V, J-V characteristics were consistent; however, at 20 V, line width increased by approximately 100%, resulting in a 50% reduction in PCE. These findings highlight the critical relationship between spraying strength, line width, and efficiency, offering valuable insights for advancing printed OPV technologies.

Organic photovoltaic (OPV) devices have attracted attention due to their high efficiency and simple manufacturing process. Applying an overlayer to OPV devices is one way to improve their performance because it can improve charge extraction and suppress vertical phase separation. In addition, dichloromethane (DCM) was used as an orthogonal solvent to minimize the effect on other layers. However, an coating problems due to the use of DCM were found, which affects surface morphology as rough or peeling. Additional research efforts are needed to solve these problems, and optimal results are expected to be obtained by utilizing various buffer layers or selective organic solvents.