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This work addresses the experimental study of zinc oxide nanowires in hybrid solar cells with P3HT. The aim of this study was the improvement of solar cell parameters by caesium seed layer doping and modification of the nanowire surface. For this, a characterisation of nanowire morphology and optical properties was performed to study consistency between the hydrothermally grown nanowires of different batches. This characterisation was necessary to be able to exclude the nanowires as reasons for the changes seen in solar cell behaviour. Moreover, for further optimisation the capping layer of P3HT and its infiltration were studied to prevent nanowires protruding through the P3HT layer, which would limit solar cell performance by shorting the device and causing a low J_sc .
These results were then used to build solar cells and study their behaviour. In a comparison caesium seed layer doped samples showed a small improvement in V_oc of 7 % over undoped samples, far below the increase seen for bilayer devices.
The spin coating of a Cs₂CO₃ metal oxide interlayer caused an increase in V_oc of 15 %.
But in conjunction with the results from the nanowire characterisation it can be concluded that this is not due to nanowire modification, but due to decreased nanowire length. Furthermore, nanowire modification with a PCBA monolayer was studied with the result of an increase in J_sc of up to 60 %. PCBA modification was also tested on devices of different nanowire length with the result of a diminishing return of J_sc increase with nanowire length increase, probably caused by a too high absorption of the P3HT covering layer on longer nanowires.