Spatially Resolved Photocurrent Mapping of Nanowire Array Solar Cells for Analysis of Factors Affecting Cell Efficiency

Sammanfattning: This thesis develops a laser-based technique for spatially resolving the photocurrent from nanowire array solar cells. The technique has been demonstrated to provide information on processing induced defects e.g. poor device contacts, and defects related to the sample e.g. missing nanowires, resolving features down to ~800nm. Moreover, the technique provides information that can be used to relate features to their effect on cell efficiency, and facilitates investigation of the possible mechanisms. An interesting result is that regions with missing nanowires contribute higher photocurrent than the uniform NW array. The application of the technique realised in this thesis is also found to be limited by various factors. Most notably, noise from the laser and artefacts produced by the electrometer limit the amount of information that can be deduced from the generated current maps. Tilting of the sample and a diffraction-limited spot size with diameter 332.5nm constitute limitations to the resolution of the technique, which was unable to categorically resolve the current from individual nanowires.