| Polymer solar cells (PSC) have been attracted world-wide attention and deeply scientific research in the recent two decades, whose power conversion efficiency has reached over 10%. Compared with the conventional Si-based courtpart, PSC devices show their unique advantages in low cost, high flexibility, light weight and so on. In this PSC research community, the major focuses are device structure optimization, high performance photovoltaic material systhesis, physical mechanism understanding, and optical designing for absorption enhancement. Our work is aim at fully realizing these advantages of PSC to promote PSC product commercialization. Indium tin oxide (ITO) transparent electrodes were wildly used in PSC devices, but the scarcity of indium on earth leads to high material cost, and their brittleness is unfavorable for device flexibility. To address these problems, our work focus on the fabrication and optimization of ITO-fress inverted PSC devices.Firstly, based on optical transfer matrix method, the optical thin-film model was built to analysis and optimize optical properties of ITO-fress inverted PSC devices. We mainly investigated the influence of metal electrode reflection for device absorption, optical properties of semi-transparent devices and the optical role of electron transport layer in inverted PSC devices. These works are able to direct practical device fabrication, and give theoretical explanation for some device physical phenomena. The devices with structure of substrate/Al/TiOx/activelayer/transparent electrode were also fabricated using the optimal parameters in optical simulation. To further improve the device stability and lifttime, a novel thin-film encapsulation method was applied through atomic layer deposition (ALD) technique. As results, ALD alumina thin film showed remarkable barrier property for water and oxygen in air, and significantly prolonged device lifttime. Meanwhile, optimal thicknesses of encapsulation layer and active layer are determined by optical simulation.To realize large-scale fabrication, avoid vaccumn equipments, be compatible with roll-to-roll processing, the development of full-solution processed devices became one hot research field. In our work, printable full-solution processed copper electrodes were prepared to replace the conventional vaccumn evaporated metal electrodes, which highly reduced fabrication cost and periode. The surface morphology, chemical composition, electrical conductivity and flexibility of printed copper were investigated in details. The printed copper showed high electrical conductivity and low surface roughness, which were very close to the vaccumn evaporated copper. Meanwhile, the printed copper owned much higher flexibility than the vaccumn evaporated one, and are capable to keep the original electrical conductivity after 1000-cycle fast bending test. ITO-fress inverted PSC devices using this printed copper electrode reached a power conversion efficicent as high as 2.77%, which is the highest one among the full-solution processed PSC devices using the same active layer materials. More importantly, the device flexibility was also higher than those using vaccumn evaporated copper electrode.Another important aspect in our work is to improve the performance of PSCs by simple and low-cost optical method. We put this part of work into 3 main parts:(1) inverted PSC devices with embedded with 1D grating structure through simple rubbing treatment, (2) inverted PSC devices with metallic 2D grating electrode, (3) cone shaped inverted PSC devices. On one hand, rubbing treatment was applied in hole transport layer to make 1D grating structure and full-solution processed copper was casted on 2D grating substrate to make 2D grating electrode, which both realized absorption and carrier mobilities improvement; on the other hand, flexilible device was warped into cone structure to trap the incident light and increase the light power usage. |
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