Organic solar cells based on bulk heterojunction (BHJ) structures have attracted considerable attention because of their low fabrication cost, mechanical flexibility, and compatibility with solution-processing techniques. In BHJ organic photovoltaic devices, nanoscale morphology and crystallinity of the photoactive layer critically influence photovoltaic performance. In this study, the effects of solvent selection and thermal annealing on crystallization evolution and photovoltaic characteristics of P3HT:PCBM organic solar cells were systematically investigated. Three different solvents, including toluene, chlorobenzene (CB), and dichlorobenzene (DCB), were employed for active-layer fabrication, followed by post-thermal annealing treatment. UV–visible absorption spectroscopy revealed solvent-dependent differences in molecular ordering and intermolecular π–π interactions within the active layer. X-ray diffraction analysis confirmed that thermal annealing significantly enhanced crystallinity and lamellar ordering of P3HT domains, particularly for CB-processed films. Electrical characterization demonstrated that solvent evaporation behavior strongly affects photovoltaic performance. Among the investigated devices, the thermally annealed CB-processed device exhibited the highest power conversion efficiency of 1.83% with an enhanced short-circuit current density of 7.057 mA cm⁻². The improved device performance is attributed to optimized crystallization behavior and balanced nanoscale phase separation induced by the moderate evaporation characteristics of CB. In contrast, although DCB-assisted films exhibited relatively strong optical absorption and enhanced crystallinity, excessively slow solvent evaporation likely induced excessive aggregation and coarse phase separation, limiting efficient photovoltaic characteristics. These results demonstrate that solvent engineering combined with thermal annealing is an effective strategy for controlling morphology evolution and crystallization behavior in P3HT:PCBM bulk heterojunction solar cells.

We investigated the properties of vanadium oxide (VOx) buffer layers deposited by a dual RF magnetron sputtering method under various target powers for inverted organic solar cells (IOSCs). Sputter fabricatged VOx thin films exhibited higher crystallinity with the increase of target power, resulting in a uniform and large grain size. The electrical properties of VOx films are improved with the increase of target power because of the increase of V content. In the results, the performance of IOSCs critically depended on the target power during the film growth because the crystalllinity of the VOx film affects the carrier mobility of the VOx film.

As energy depletion and environmental pollution problems are intensified, research has been conducted actively on alternative energy sources, an eco-friendly and continuous available energy conversion system. So has been organic solar cells whose efficiency is improved to 18.32%. The photoactive layer inside the solar cell is composed of a donor and a acceptor, and the combination of materials capable of effectively exchanging electrons greatly affects the efficiency of the organic solar cell. Accordingly, various researches have been conducted to improve the efficiency, and the maximum efficiency could be achieved by a solar cell with high carrier generation and low charge recombination characteristics through the introduction of a non-fullerene acceptor and material reconstruction. Organic solar cells are still difficult to commercialize due to their efficiency limitations and light stability, but if a photoactive layer consisting of a donor capable of efficiently absorbing long-wavelength light and an acceptor capable of forming an appropriate energy level is designed, the efficiency of the organic solar cell will reach 20%.

Recently many efforts have been made to develop a novel class of non-fullerene electron acceptor materials for highperformance organic solar cells. In this work, anthraquinone derivatives, TMAQ and THAQ, were prepared and their availability as electron acceptor materials for organic solar cells were investigated in terms of optical, thermal, electrochemical properties, and solar cell devices. Compared to TMAQ, a significant bathochromic shift of absorption band was observed for THAQ owing to intramolecular hydrogen-bond-assisted CT interactions. Thanks to the fused aromatic ring structure and benzoquinone unit, both TMAQ and THAQ exhibited a high thermal stability and an efficient electron reduction process. In particular, the intramolecular O-H---O=C hydrogen bond of THAQ plays an important role in improving the thermal stability and electron reduction properties. In the P3HT:acceptor solar cell system, THAQ-based devices had more than ca. 6 times higher power conversion efficiency than TMAQ -based devices. These results serve as a guide for developing high-efficient anthraquinonebased electron acceptor materials.

In this study, composite transparent electrodes were fabricated either from a conductive polymer poly(3,4- ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) or silver nanowire (AgNW). Three transparent electrodes such as PEDOT:PSS, PEDOT:PSS and AgNW mixture, and AgNW were fabricated. As for a transparent electrode, measured sheet resistance values were 89.6, 60.6 and 28.6 Ω/sq, and the transmittance values were 80.2, 82.0 and 83.8% while surface roughness (Rq) values were 4.1, 8.1, 20.4 nm for PEDOT:PSS, PEDOT:PSS and AgNW mixture, and AgNW, respectively. To verify the overall performance of these composite electrodes, we applied these electrodes to the top electrode of the solution-processed organic solar cells (OSCs). PEDOT:PSS provided the best performance with a fill factor (FF) of 51.2% and a photoconversion efficiency (PCE) of 2.2%, while traditional metal top electrode OSC provided FF of 60.5% and PCE of 3.1%.

The power conversion efficiency of organic polymer solar cells was enhanced by introducing a ferroelectric polymer layer at the interface between active layer and metal electrode. The power conversion efficiency was increased by 50% through the enhancement of the open circuit voltage. To investigate the role of the ferroelectric layer on the dissociation process of the excitons, non-radiative portion of the exciton decay was directly measured by using photoacoustic technique. The results show that the ferroelectric nature of the buffer layer does not play any roles on the dissociation process of the excitons, which indicates the efficiency enhancement is not due to the ferroelectricity of the buffer layer.

The characterizations of zinc oxide (ZnO) buffer layers grown by unbalanced magnetron (UBM) sputtering under various substrate temperatures for inverted organic solar cells (IOSCs) were investigated. UBM sputter grown ZnO films exhibited higher crystallinity with increasing the substrate temperature, resulting in uniform and large grain size. Also, the electrical properties of ZnO films are improved with increasing substrate temperature. In the results, the performance of IOSCs critically depended on the substrate temperature during the film growth because the crystalllinity of the ZnO film affect the carrier mobility of the ZnO film.

In this research, nanocomposite layers consisting of poly (3,4,-ethylene dioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) and CuO nanoparticles were investigated as hole transport layers in organic solar cells based on poly (3-hexylthiophene) (P3HT) as the electron donor and (6.6) phenyl-C61-butyric acid methyl ester (PCBM) as the electron acceptor. The addition of CuO nanoparticles to PEDOT:PSS layer improved the solar cell performance with 0.5% CuO nanoparticle concentration. At optimized concentration, CuO mixed PEDOT:PSS films had good electrical (4.131 Ω?cm) and optical (transmittance > 90%) properties for using hole transporting layer. We investigated that improved solar cell performance with CuO nanoparticles mixed PEDOT:PSS films.