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UBC Theses and Dissertations

Design and fabrication of polythiophene-based organic photovoltaic devices on glass and plastic substrate Ebadian, Soheil


This thesis reports our various experimental and theoretical work on design and fabrication of organic bulk hetero junction photovoltaic devices based on P3HT:PCBM blends, fabricated on glass and plastic. This work compares several measured characteristics of these devices so as to bring insight on the effect of annealing and regioregularity of the polymer on the photovoltaic characteristic of the devices. More specifically, we present the fabrication method of P3HT:PCBM organic photovoltaic devices on glass and plastic. By comparing the low and high regioregular (RR) P3HT samples used for fabrication of solar cells, we conclude that devices based on higher RR P3HT are more prone to degradation. The low RR device, on the other hand, demonstrates an increase in the hole mobility in post-annealed conditions as thermal annealing causes a more effective π - π stacking. This leads to unchanged or even higher power conversion efficiency (PCE) of the devices with lower regioregularity after thermal annealing. For the same reason, the low RR devices are found to be more stable during a four month degradation analysis while the efficiency of high RR device decreases drastically in the same period of time. We also present a method for reducing the roughness of polyethylene terephthalate (PET) substrates for fabrication of organic photovoltaics. Using PEDOT:PSS we have been able to reduce the roughness drastically and have increased the yield by decreasing the possibility of top-bottom electrode short circuit. In this method the PEDOT:PSS is deposited on the substrate in a 2-step method that makes the substrate smoother and more uniform before P3HT:PCBM deposition.

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