Yameng Bao

Effect of substrate pretreatments on the atomic layer deposited Al2O3 passivation quality

The authors show here that the passivation quality of Al2O3 is highly sensitive to the surface condition prior to the atomic layer deposition, affecting especially the thermal stability of the film. Pretreatments like diluted HCl bath or preheating at 200 °C both improved significantly the passivation quality and thermal stability of the films. In addition, the authors observed that a thin chemical SiO2 layer resulting from diluted HCl solves the blistering problem often encountered in H2O based atomic layer deposited process. Finally, the authors show that the chemical oxide protects the surface from contaminants, enabling long storage times in a dirty ambient between the cleaning and the film deposition.

Effect of ALD reactants on blistering of aluminum oxide films on crystalline silicon

Atomic layer deposited aluminum oxide (Al2O3) has in recent years proven to be a promising surface passivation material for crystalline silicon solar cells. However, blistering in Al2O3 films is a common problem deteriorating the surface passivation quality. Here, blistering is studied from material aspects including film thickness, film composition and postdeposition heat treatment. We show how thicker films, higher annealing temperatures and longer annealing times lead to more severe blistering and demonstrate how blistering can be avoided by using either O3 as the oxidant or depositing a thin TiO2 layer at the silicon interface.

Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell

This data article is related to the recently published article ‘20.8% industrial PERC solar cell: ALD Al2O3 rear surface passivation, efficiency loss mechanisms analysis and roadmap to 24%’ (Huang et al., 2017) [1]. This paper is about passivated emitter and rear cell (PERC) structures and it describes the quality of the Al2O3 rear-surface passivation layer deposited by atomic layer deposition (ALD), in relation to the processing parameters (e.g. pre-clean treatment, deposition temperature, growth per cycle, and film thickness) and to the cell efficiency loss mechanisms. This dataset is made public in order to contribute to the limited available public data on industrial PERC cells, to be used by other researchers.

Data of the recombination loss mechanisms analysis on Al2O3 PERC cell using PC1D and PC2D simulations

This data article is related to our recently published article (‘20.8% industrial PERC solar cell: ALD Al2O3 rear surface passivation, efficiency loss mechanisms analysis and roadmap to 24%’, Huang et al., 2017 [1]) where we have presented a systematic evaluation of the overall cell processing and a cost-efficient industrial roadmap for PERC cells. Aside from the information already presented in Huang et al., 2017 [1], here we provide data related to Sectin 3 in Huang et al., 2017 [1] concerning the analysis of the recombination losses׳ mechanisms by PC1D V5.9 and PC2D simulations (Clugston and Basore, 1997, Basore and Cabanas-Holmen, 2011, Cabanas-Holmen and Basore, 2012 and Cabanas-Holmen and Basore, 2012.) [2], [3], [4], [5] on our current industrial Al2O3 PERC cell. The data include: i) PC2D simulations on J02, ii) the calculation of series resistance and back surface recombination velocity (BSRV) on the rear side metallization of PERC cell for the case of a point contact, and iii) the PC1D simulation on the cumulative photo-generation and recombination along the distance from the front surface. Finally, the roadmap of the solar cell efficiency for an industrial PERC technology up to 24% is presented, with the aim of providing a potential guideline for industrial researchers.

Silicon surface passivation with atomic layer deposited aluminum nitride

We propose a new surface passivation material for crystalline silicon solar cells, namely atomic layer deposited aluminium nitride (ALD AlN). AlN has multiple benefits as compared to more commonly used Al2O3, i.e. it has better optical properties, higher hydrogen concentration and better suitability for phosphorous emitter passivation due to lower fixed charge. In addition to introducing a new ALD passivation material, we study here various deposition temperatures and postdeposition heat treatments. The best surface passivation quality is reached with high deposition temperatures followed by a combination of longer low temperature anneal and a short high temperature firing. With the optimized parameters, extremely low interface defect density values of ~4·1011 eV-1cm-2 are reached demonstrating the potential of ALD AlN as future surface passivation material.

Mixed aluminum precursor in the atomic layer deposited Al 2 O 3 for effective silicon emitter passivation

In this contribution, we have studied the impact of aluminum precursor of atomic layer deposited (ALD) AI2O3 on the passivation quality of silicon solar cell emitters. Aluminum precursors, Trimethylaluminum (TMA) and Dimethylaluminum chloride (DMACl), and their different combinations were used to deposit Al2O3 layers on both phosphorus and boron implanted emitters. In addition to measuring the passivation quality, the wafers experienced thermal stability investigation. In all wafers, Al2O3 resulted in better emitter saturation current as compared to thermal oxide resulting from ion implantation drive-in anneal. On industrial type of emitters, values around Joe at 60 fA/cm2 were obtained. The impact of aluminium source was not as high as expected, however, we found that aluminium precursor has a high impact on the formation of so-called blisters. We show that the blisters can be greatly suppressed using DMACl as the aluminium precursor while TMA results in the formation of high-density and large-size blisters. Our PERC solar cell with the DMACl in the ALD process showed similar passivation quality as the TMA-based process.