INES

Driven by the relatively high cost of silver (Ag), interest has grown in the photovoltaic (PV) industry to substitute conventional screen printed (SP) Ag front contacts with copper (Cu) plated contacts. The approach chosen here applies selective laser ablation of the front anti-reflection coating (ARC), then forming self-aligned nickel silicides (NiSi x ) contacts, and thickening the lines by Cu plating to achieve the desired line conductivity. A successful implementation of this scheme requires annealing to form NiSi x with low contact resistance. However, it has been shown that industrial shallow emitters can be damaged severely upon conventional annealing of nickel. In this paper, we show that by using large area excimer laser annealing (ELA), NiSi x contacts can be formed on industrial shallow emitters without the associated junction degradation. On the basis of sheet resistance, transmission electron microscopy, and lifetime measurements, we demonstrate that NiSi x formation by ELA can be achieved in narrow contact openings without damaging the passivation and reflectance properties of the neighboring ARC. In addition, the thresholds for NiSi x formation for different Ni thicknesses are quantified by rigorous finite element simulations and compared with experimental data. Finally, high efficiency passivated emitter and rear cell type solar cells featuring a shallow 85 Ω/sq emitter have been processed on large area CZ-Si using laser ablation of the ARC and subsequent NiSi x formation by ELA. These cells show an average efficiency gain of 0.4% abs compared with cells processed with reference SP contacts. In this work, the best performing cell with the ELA process reached 20.0% energy conversion efficiency.

In this work, we report on a self-aligned nickel silicide formation technique based on excimer laser annealing (ELA). We evaluate this process for the front contact formation of industrial PERC type solar cells on random pyramid textured Si surfaces where damage to surface texture, emitter passivation, or to the shallow junction should be avoided or minimized. PERC type solar cells obtained by POCl 3 diffusion were processed on large area (12.5x12.5 cm 2 ) CZ-Si. Self-aligned litho-free Ni/Cu contacts defined by ps-laser ablation of the SiO 2 /SiN x anti-reflective coating (ARC) and subsequent ELA of the Ni layer were compared to conventional Ag screen printed contacts. The novel ELA process results in an absolute gain in Jsc of 0.8 mA/cm 2 as well as a drop of 0.3 Ω.cm 2 in series resistance (Rs) compared to SP Ag contacts due to reduced shading and resistance losses. This leads to 0.5% absolute increase in efficiency from 19.3% to 19.7% since other characteristics (Voc, pFF) could be maintained to the same level. In this work, the best performing cell with the ELA process reached an outstanding 20.0% energy conversion efficiency with Jsc=39.3 mA/cm 2 , Voc=649.8mV, and FF=78.3%.

The role of transparent conducting oxides (TCO) on the front side of amorphous/crystalline (c-Si) silicon heterojunction solar cells (HJ) is of great importance for high efficiency solar cells. They have to fulfil high transparency and high electrical conductivity. Then, device performance can be increased if an appropriate front side scheme is incorporated into the cell device because of a direct impact either on short-circuit current (J SC ) and fill factor (FF). Indium Tin Oxide (ITO) has demonstrated to be a very good candidate to get the best optical/electrical compromise: low resistivity values can be achieved thanks to relatively high free carrier concentration (N d > 2·10 20 cm -3 ), though absorption in the IR range is still a limiting factor for high J SC devices. In this work, we introduce the laser treatments of ITO by Excimer laser annealing (ELA) as an interesting approach to improve the optical/electrical compromise of the material. First, we have studied the changes in material properties when irradiating with different laser conditions. Then, we have looked at the effect of these laser treatments on the passivation properties of HJ precursors. Finally, complete HJ solar cells have been fabricated with laser annealed ITOs at optimal conditions.

This paper presents results of the measurement of solute diffusivities in the Al-Ni and Sn-Bi-In systems. These experiments were conducted in microgravity and may therefore be assigned as reference values. A dedicated facility, which can be used for processing of four identical samples in parallel, was developed for the experiments under consideration. In addition, a rather thorough analysis of possible error sources in shear cell type experiments is carried out. Comparison with work carried out using magnetic fields to control convective flows, and with previous indirect measurements results, is also provided. A coherent picture emerges from the overall agreement between various measurements, and the data from the current work can thus be considered as reference benchmarks for future experiments. Another conclusion of the present study is that the shear cell technique is well suited for the measurement of solute diffusivities.

Undoped and Ge-doped CdTe crystals have been grown using the dewetting phenomenon on the earth. A gap effected by the dewetting between the crystal and ampoule was created with a thickness up to 60 mm, but it was not stable for the complete growth process. The dewetting was stable for the first 25 mm of the growth, but than it got unstable. The main deteriorating factor was a change of a liquid-solid interface shape from the convex to concave. Structural, electrical, photoelectrical and optical characteristics of the studied samples showed better material quality in dewetted areas. r