Evolution of oxide disruptions: The (W)hole story about poly-Si/c-Si passivating contacts

Lee

Progress in Photovoltaics

et al. 2019

This study proposes a hybrid solar cell structure for a highly efficient silicon solar cell obtained by combining two passivating contact structures, namely, a heterojunction and polysilicon passivating contact. Given that the major cause of the loss in efficiency of crystalline silicon solar cells is carrier recombination at the metal‐semiconductor junction, a passivating contact having high‐quality passivation and a low contact resistance was introduced. In this study, two major passivating contact solar cells were combined. By applying an intrinsic thin amorphous silicon layer at the front and a tunneling oxide at the rear, a hybrid silicon solar cell with an efficiency of 21.8% was fabricated. Moreover, to evaluate the potential efficiency limit and to suggest methods for improving the cell performance of the proposed amorphous silicon emitter tunnel oxide back contact structure, the cell efficiency was simulated, and the result indicated that an efficiency of 26% could be achieved by controlling the thickness and resistivity of the wafer.

Section: Resultsmentioning

confidence: 98%

mentioning

confidence: 99%

Tunnel oxide passivating electron contacts for high‐efficiency n‐type silicon solar cells with amorphous silicon passivating hole contacts

Lee

Progress in Photovoltaics

et al. 2019

Progress in Photovoltaics

“…It was suggested that both mechanisms possibly superimpose in real junctions, in particular for the case of interfacial oxides with thicknesses d ox < 1.5 nm formed by wet-chemical or ozone oxidation. 16 Experimentally, the existence of pinholes-also in samples with good passivation quality-has been verified by transmission electron microscopy (TEM) 17 and by selective etching of the poly-Si from the interfacial oxide after junction formation. 18 For samples with interfacial oxide thicknesses in excess of 2 nm, the etch pit density is in excellent agreement with the pinhole areal density as predicted by the pinhole model for the measured J 0 , ρ C values and doping profiles of the same samples.…”

Section: Introductionmentioning

confidence: 96%

Modeling recombination and contact resistance of poly‐Si junctions

Folchert

Peibst

Brendel

2020

Self Cite

We present a semi-analytical model for the calculation of the current through and the recombination in carrier-selective junctions consisting of a poly-Si/SiO x /c-Si layer stack. We calculate the recombination parameter J 0 and the contact resistance ρ C after solving the band-bending-problem on both sides of the interfacial oxide. Comparisons with finite-element simulations show that the current calculation is reliable at all bias conditions except for inversion and that current through pinholes is resolved adequately in the model. The model allows a coherent description of lifetime-, current-voltage-and capacitance-voltage measurements performed on a sample with dominant tunneling. We use our model to investigate the influence of oxide thickness and pinhole density on J 0 and ρ C of our state-of-the-art poly-siliconon-oxide (POLO) junctions and demonstrate its usefulness for the optimization of poly-Si based junctions.

Physica Status Solidi (a)

“…The SiO x layer is generally thin enough (<2 nm) to allow a transport by tunneling. However, it has been shown that the SiO x integrity is altered upon annealing leading to the hypothesis of a direct transport through pinholes within the SiO x layer . Recent studies focus on the detection of pinholes through SiO x layer, notably by means of conductive Atomic Force Microscopy (C‐AFM) …”

Section: Introductionmentioning

confidence: 99%

Conductivity and Surface Passivation Properties of Boron‐Doped Poly‐Silicon Passivated Contacts for c‐Si Solar Cells

Morisset

Cabal

Grange

et al. 2018

Passivating the contacts of crystalline silicon (c‐Si) solar cells with a poly‐crystalline silicon (poly Si) layer on top of a thin silicon oxide (SiOx) film are currently of growing interest to reduce recombination at the interface between the metal electrode and the c‐Si substrate. This study focuses on the development of boron‐doped poly‐Si/SiOx structure to obtain a hole selective passivated contact with a reduced recombination current density and a high photo‐voltage potential. The poly‐Si layer is obtained by depositing a hydrogen‐rich amorphous silicon layer by plasma enhanced chemical vapor deposition (PECVD) exposed then to an annealing step. Using the PECVD route enables to single side deposit the poly Si layer, however, a blistering of the layer appears due to its high hydrogen content, which leads to the degradation of the poly‐Si layer after annealing. In this study, the deposition temperature and gas flow ratio used during PECVD step are optimized to obtain blister‐free poly‐Si layer. The stability of the surface passivation properties over time is shown to depend on the blister density. The surface passivation properties are further improved thanks to a post process hydrogenation step. As a result, a mean implied photo‐voltage value of 714 mV is obtained.