Development of ZnO nanowire based CdTe thin film solar cells

- Cells which incorporate ZnO nanowire buffer layers of up to 9.5% achieved.
- Impact of nanowires upon subsequent layer growth and device processing discussed.
- Limitations of the use of ZnO nanowires in cell structures is established.

This work reports on the development of CdTe thin film solar cells grown on ZnO nanowire arrays. The focus was placed on utilising ZnO nanowire arrays as a replacement to the conventional ZnO thin film buffer layer, thereby requiring minimal alteration to the existing solar cell structure. Incorporation of nanowires was found to alter subsequent film growth and processing, with the nanowire dimensions changing device performance significantly. Shorter, ~100 nm, wires were found to produce particularly low device performance of <0.5% whilst longer wires in the range 250-2000 nm were able to produce more functional cells. Working devices of up to 9.5% efficiency were achieved through the production of “embedded tip” nanowire solar cells. Variation of the nanowires length demonstrated that the nanowires were involved in carrier recombination and that this may be the performance limiting factor.