Multicrystalline silicon thin film solar cells on glass with epitaxially grown emitter prepared by a two-step laser crystallization process

Abstract

In this paper, we demonstrate a two‐step laser crystallization process for thin film silicon solar cells on glass. In a first step a 5 µm thick amorphous silicon layer is crystallized by a diode laser to get the absorber. The multicrystalline layer consists of grains with sizes in the range of 1 mm to 10 mm. In a second step a thin amorphous silicon layer is epitaxially crystallized by an excimer laser to form the emitter.Epitaxy was investigated in a fluence range of 700 to 1200 mJ/cm2. The resulting thickness of the emitter is measured and numerically simulated, both resulting in 185 nm for a fluence of 1100 mJ/cm2. The solar cells achieve maximum open circuit voltages of 548 mV, short‐circuit current densities of up to 22.0 mA/cm2 and an efficiency of 8.0%.

Multicrystalline Silicon Thin‐Film Solar Cells Based on Vanadium Oxide Heterojunction and Laser‐Doped Contacts

“…Consequently, considering this effect, J sc can be calculated using the active area instead of aperture area, which results in 19.07 mA cm −2 without PDMS foils and 20.16 mA cm −2 with it. These values agree with previous thin‐film solar cells fabricated by our research group and lead to an active‐area efficiency of 5.6%. It must be mentioned that these values are reached without texturing the silicon surface to enhance the light trapping, introducing remarkable optical losses at longer wavelengths …”

PEDOT:PSS emitters on multicrystalline silicon thin-film absorbers for hybrid solar cells

“…This can be improved by utilizing a good light trapping scheme by nanostructures, e.g., nanowires etched into the silicon layer. 15 Therefore, further work will be targeted on the deposition of PEDOT:PSS on the nanowires for light trapping.…”

“…The resulting multicrystalline silicon layer was hydrogen-passivated by a remote plasma treatment at a heater temperature of 400-600 C and a gas flow rate of 10 sccm (80% hydrogen and 20% argon). 15 In order to remove surface contaminations, the top 200 nm layer of the 5 lm thick mc-Si was removed by isotropic etching in a solution containing KMnO 4 :HF (2%) with a weight ratio of 1:1000. 16 Subsequently, the substrates were dipped in 2% HF for 2 min to remove the native oxide.…”

Thermal stresses and cracking behavior during laser crystallization of silicon on glass for thin film solar cells

“…During the cooling phase, the silicon crystallizes leading to grains of some 100 µm in length. Conversion efficiencies of 8% where reached with these two concepts . However, in both cases cracks occur due to the high temperature gradients introduced by the localized crystallization techniques .…”

“…State of the art production of such cells is done by crystallizing silicon of several micrometers in thickness. First amorphous silicon is deposited by electron beam evaporation (EBE) and then crystallized, either by an electron beam in vacuum or by laser irradiation in ambient air . In both cases, the silicon layer is heated up rapidly within some milliseconds so that it melts.…”