Yu Gu

Efficient Polymer Solar Cells Based on Benzothiadiazole and Alkylphenyl Substituted Benzodithiophene with a Power Conversion Efficiency over 8

A new copolymer PBDTP-DTBT based on benzothiadiazole and alkylphenyl substituted benzodithiophene is synthesized and characterized. The correlation of the evolution of the morphology and photovoltaic performance is investigated. The power conversion efficiency of the polymer solar cells based on PBDTP-DTBT/PC71 BM (1:1.5, w/w) reaches up to 8.07%, under the irradiation of AM 1.5G, 100 mW/cm(2) .

Efficient Polymer Solar Cells Based on a Low Bandgap Semi‐crystalline DPP Polymer‐PCBM Blends

Solar cell performance and morphology characterization of a diketopyrrolopyrrole-based low bandgap polymer is reported. The polymer adopts an H-type aggregation and solvent mixture processing gives a better morphology. The morphology evolution is characterized by combined GIXD and GISAXS experiments and a four step morphology development mechanism is proposed.

Guided crystallization of P3HT in ternary blend solar cell based on P3HT:PCPDTBT:PCBM

To mimic the performance of the tandem solar cells, ternary blend solar cells with a single active layer of P3HT:PCPDTBT:PC61BM were cast from chlorobenzene and thermally annealed. By varying blending ratio, thermal annealing time and P3HT molecular weight, the device performance was enhanced relative to the binary references. To understand this, the morphology of the active layer was studied using hard and soft X-ray scattering methods in concert with bright field and energy resolved transmission electron microscopies. We found that the phase separation of the amorphous PCPDTBT and P3HT guided the formation of P3HT fibrils, resulting in a unique multi-length-scale morphology. This morphology consisted of bundles of well-defined P3HT fibrils, forming a network, imbedded in an amorphous mixture of the PCBM, PCPDTBT and P3HT. The two polymers acted independently in their specific photoactive ranges, and the sensitization of PCPDTBT benefited the cascade charge transfer. This multi-length-scale morphology was linked to the improved device performance of P3HT:PCPDTBT:PC61BM and the photophysics of the active layer.

Morphology study on ternary blend polymer solar cell to achieve improved device performance

Ternary blend solar cells are considered presents one route to construct the devices with a broad absorption of the solar spectrum. However, the morphological studies on such mixtures have been limited. Here, the morphology of P3HT/PCPDTBT/PC61BM ternary blend thin films were studied. By adjusting the blending ratio of two polymers, P3HT molecular weight, thermal annealing time and spin-coating solvents, the crystallinity of both polymers and phase separation among each component were controlled. It was found that a high crystallinity of the polymers is important for good device performance. Due to the crystallization of the polymers and the immiscibility between P3HT and PCPDTBT, a hierarchical morphology was generated that mimicked a tandem cell connected in parallel and extended the absorption. In addition, the amorphous PCPDTBT was found to guide the orientation of P3HT nanocrystals before they merged into fibrils, and it also served as a photosensitizer to form a cascade energy level alignment. Therefore, the two polymers worked synergistically to achieve the improved device performance relative to the binary reference.