Thin‐film polycrystalline silicon solar cells formed by diode laser crystallisation

Abstract

Polycrystalline silicon films of 10 mm thickness are formed on glass in a single-step continuous wave diode laser crystallisation process, creating large crystal grains up to 1 mm wide and 10 mm long. Solar cells are formed on the layers by employing a rear point contacting scheme. Intermediate layers between the glass and the silicon are shown to heavily influence the cell characteristics. A stack of silicon oxide/silicon nitride/silicon oxide has produced the best cell efficiency so far of 8.4 % with open-circuit voltage of 557 mV. With simple optimisation of the contacting scheme, 10 % efficient cells are expected in the near future.

Performance potential of low-defect density silicon thin-film solar cells obtained by electron beam evaporation and laser crystallisation

“…5, right presence of nitrogen contamination which can be negatively affecting the voltages. The best performing metallised 7.8%-efficient cell on the O/C/O triple layer stack has V OC of 526 mV, similar to V OC of the cells on the oxide only but an improvement in cell antireflection properties due to presence of a very thin SiC x layer on the front leads to a significant current gain, 26 mA/cm 2 versus 24 mA/cm 2 for the cell on SiO x [11].…”

“…Sputtered Al is then used to form contacts to the n-and p-type openings. This metallisation is very similar to the one described in [11] but simplified by reducing the contact density and no heavy Si doping under the p-type contacts to the absorber to accommodate and facilitate quicker cell development. Current research-level planar cells rely on a pigmented rear diffuse reflector for modest light-trapping.…”

“…The cell voltages depend on the intermediate dielectric layers, which is discussed elsewhere [11,12]. The cells on SiO x achieve V OC in a range of 520-540 mV, while the cells on SiN x have the poorest V OC , below 500 mV.…”

“…Transparent dielectric films, SiO x , SiC x , and SiN x , and their different combinations were tested as the intermediate layers, along with their interactions with laser beam parameters. Properties of different intermediate layers and their effects on cell performance are described in detail elsewhere [11,12]. No single layer alone can perform all required functions.…”

“…The IQE is adjusted to take into account parasitic absorption in the SiC x layer, which was measured prior to silicon deposition, as presented in [11]. The IQE peaks at around 90% and it stays around this value for most of the visible wavelength range.…”