Patricia Prod'Homme

Nanophotonics for ultrathin crystalline silicon photovoltaics: When photons (actually) meet electrons

Nanopatterning has recently demonstrated to be an efficient method for boosting the light absorption of thin films (< 50 μm) of crystalline silicon. However, convincing solar cell results are still missing. The goal of the European project PhotoNVoltaics is to investigate the impacts that nanopatterns have on thin crystalline silicon solar cells and to identify the conditions for their efficient integration. The present contribution presents the main findings of the consortium so far. Optical modeling and optimization of nanopatterned thin-film c-Si cells have indicated a few trends regarding the design of the optimum pattern for 1-40 μm thin foils: merged inverted nanopyramids, with their progressive profile seem to provide the best combination of antireflective and light trapping properties, together with negligible surface damage and best coating template for subsequent process steps. But despite the high Jsc enhancement that these nanopatterns are expected to bring, and despite the higher efficiency of these nanophotonic structures for 1-2 μm-thin foils, the absolute Jsc values indicate that thicker foils will have to be preferred if direct competition with wafer-based and thin-film technologies is concerned. An ideal structure is taking shape as an IBC heterojunction cell, with a frontside nanopattern and a thickness of 40 μm.

Interdigitated back contact silicon solar cells: Diode and resistance investigation at nanoscale using Kelvin Probe Force Microscopy

The use of Kelvin Probe Force Microscopy to investigate PN junctions under illumination and electrical bias has been shown to be an effective way to analyze the electrical properties of solar cells at the nanoscale. We use it here, for the first time, on interdigitated back contact solar cells. Measurements are performed between the metallic fingers under an electrical bias in the dark and under illumination in open circuit conditions. Our results show that that KPFM could be used to identify and localize diodes resistance losses at the nanoscale.