Low surface recombination in silicon-heterojunction solar cells with rear laser-fired contacts from aluminum foils

In this study, an approach to create laser-fired contacts from aluminum foils is studied on p-type silicon-heterojunction solar cells. This alternative approach consists of the use of aluminum foils instead of evaporated layers as a metal source and rear electrode for the laser-firing process. A q-switched infrared laser (1064 nm) was employed to create the local point contacts. Quasi-steady-state photoconductance measurements evidenced a limited degradation in the surface passivation quality during the laser-firing process. Heterojunction solar cells fabricated with these rear contacts reached a best conversion efficiency of 18% with a remarkable open-circuit voltage of 690 mV. These values were very close to those of reference devices fabricated with evaporated aluminum layers. This result suggests a similar effect on the rear surface passivation by both contact strategies. However, external quantum efficiency curves revealed a better response from devices with a rear aluminum foil in the near infrared. Optical measurements indicate that this effect can be related to a higher internal reflection at the back surface. Consequently, laser-fired contacts from aluminum foils appear to be a fast and convenient solution for the rear contact of high-efficiency silicon solar cells.Postprint (published version

Surface passivation and optical characterization of Al2O3/a-SiCx stacks on c-Si substrates

The aim of this work is to study the surface passivation of aluminum oxide/amorphous silicon carbide (Al2O3/a-SiCx) stacks on both p-type and n-type crystalline silicon (c-Si) substrates as well as the optical characterization of these stacks. Al2O3 films of different thicknesses were deposited by thermal atomic layer deposition (ALD) at 200 °C and were complemented with a layer of a-SiCx deposited by plasma-enhanced chemical vapor deposition (PECVD) to form anti-reflection coating (ARC) stacks with a total thickness of 75 nm. A comparative study has been carried out on polished and randomly textured wafers. We have experimentally determined the optimum thickness of the stack for photovoltaic applications by minimizing the reflection losses over a wide wavelength range (300–1200 nm) without compromising the outstanding passivation properties of the Al2O3 films. The upper limit of the surface recombination velocity (Seff,max) was evaluated at a carrier injection level corresponding to 1-sun illumination, which led to values below 10 cm/s. Reflectance values below 2% were measured on textured samples over the wavelength range of 450–1000 nm.Postprint (published version

Base contacts and selective emitters processed by laser doping technique for p-type IBC c-Si solar cells

Abstract In this work, we describe a novel fabrication process of p-type interdigitated back contact (IBC) silicon solar developed by means of laser doping and laser firing techniques. We use dielectric layers both as dopant sources to create highly-doped regions and as passivating layers. In particular, we use phosphorus-doped silicon carbide stacks (a-SiCx (n)) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and aluminum oxide (Al2O3) layer deposited by atomic layer deposition (ALD). Emitters were fabricated with a light thermal phosphorus diffusion in order to reduce bulk and surface emitter recombination losses. Highly doped regions n++ (emitter) and p++ (base) were simultaneously created in a point-like structure using a pulsed Nd-YAG 1064 nm laser in the nanosecond regime by laser processing the dielectric layers. The results obtained for a cell, 3x3 cm2, are presented. Efficiencies up to 18.1% (Jsc = 39 mA/cm2, Voc = 632 mV, FF = 73.4%) have been achieved in our fabricated IBC cells.Postprint (published version

Transition metal oxides as hole-selective contacts in silicon heterojunctions solar cells

This work reports on a comparative study comprising three transition metal oxides, MoO3, WO3 and V2O5, acting as front p-type contacts for n-type crystalline silicon heterojunction solar cells. Owing to their high work functions (>5 eV) and wide energy band gaps, these oxides act as transparent hole-selective contacts with semiconductive properties that are determined by oxygen-vacancy defects (MoO3-x), as confirmed by X-ray photoelectron spectroscopy. In the fabricated hybrid structures, 15 nm thick transition metal oxide layers were deposited by vacuum thermal evaporation. Of all three devices, the V2O5/n-silicon heterojunction performed the best with a conversion efficiency of 15.7% and an open-circuit voltage of 606 mV, followed by MoO3 (13.6%) and WO3 (12.5%). These results bring into view a new silicon heterojunction solar cell concept with advantages such as the absence of toxic dopant gases and a simplified low-temperature fabrication process.Preprin

Low surface recombination in silicon-heterojunction solar cells with rear laser-fired contacts from aluminum foils

In this study, an approach to create laser-fired contacts from aluminum foils is studied on p-type silicon-heterojunction solar cells. This alternative approach consists of the use of aluminum foils instead of evaporated layers as a metal source and rear electrode for the laser-firing process. A q-switched infrared laser (1064 nm) was employed to create the local point contacts. Quasi-steady-state photoconductance measurements evidenced a limited degradation in the surface passivation quality during the laser-firing process. Heterojunction solar cells fabricated with these rear contacts reached a best conversion efficiency of 18% with a remarkable open-circuit voltage of 690 mV. These values were very close to those of reference devices fabricated with evaporated aluminum layers. This result suggests a similar effect on the rear surface passivation by both contact strategies. However, external quantum efficiency curves revealed a better response from devices with a rear aluminum foil in the near infrared. Optical measurements indicate that this effect can be related to a higher internal reflection at the back surface. Consequently, laser-fired contacts from aluminum foils appear to be a fast and convenient solution for the rear contact of high-efficiency silicon solar cells

The use of ferrofluids in the forensic examination of magnetic recordings

SIGLEAvailable from British Library Document Supply Centre- DSC:7072.798(HO-SRDB-P--15/89) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Recovery of indium-tin-oxide/silicon heterojunction solar cells by thermal annealing

Postprint (published version