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Degradation of P3HT:PCBM-based conjugated polymer solar cells Shambayati, Shabnam


This work examines the effect of regioregularity (RR) and zinc oxide (ZnO) nanoparticle doping on the degradation of poly(3-hexylthiophene) (P3HT):6,6-phenyl C₆₁-butyric acid methyl ester (PCBM) organic solar cells. This is done through application of semi-compact models that relate experimentally measured transport characteristics to structural properties. In this way, the contribution of regioregularity and ZnO nanoparticles to the change in structural properties can be quantified. These models allow interpretation of experimental data and insight into the underlying degradation mechanisms. In this thesis, the mobility edge model is used, and corresponding parameters such as effective electron and hole mobilities are extracted and compared. These results show that studying electron transport plays a critical role in understanding the degradation of P3HT:PCBM solar cells. Examination of regioregular devices reveals that the drop in effective electron mobility with annealing for the high RR devices is greater than that of the low RR ones. This is attributed to the greater tendency for crystallization-driven phase segregation in blends of 98% RR P3HT and PCBM. In hybrid polymer-ZnO devices, effective electron mobility improves with the addition of an optimal concentration of ZnO. The decline in electron effective mobilities with annealing is smaller for the devices containing ZnO in comparison to devices without ZnO. Studying the morphology of these devices shows that the phase segregation is identical for devices with and without ZnO.

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