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We present a novel process sequence to simplify the rear-side patterning of the silicon heterojunction interdigitated back contact (HJ IBC) cells. In this approach, interdigitated strips of a-Si:H (i/p(+)) hole contact and a-Si:H (i/n(+)) electron contact are achieved by partially etching a blanket a-Si:H (i/p(+)) stack through an SiOx hard mask to remove only the p(+) a-Si:H layer and replace it with an n(+) a-Si:H layer, thereby switching from a hole contact to an electron contact in situ, without having to remove the entire passivation. This eliminates the ex situ wet clean after dry etching and also prevents re-exposure of the crystalline silicon surface during rear-side processing. Using a well-controlled process, high-quality passivation is maintained throughout the rear-side process sequence leading to high open-circuit voltages (V-OC). A slightly higher contact resistance at the electron contact leads to a slightly higher fill factor (FF) loss due to series resistance for cells from the partial etch route, but the FF loss due to J(02)-type recombination is lower, compared with reference cells. As a result, the best cell from the partial etch route has an efficiency of 22.9% and a V-OC of 729 mV, nearly identical to the best reference cell, demonstrating that the developed partial etch process can be successfully implemented to achieve cell performance comparable with reference, but with a simpler, cheaper, and faster process sequence. European Commission's Horizon 2020Framework Programme, Grant/Award Num-ber: 727523; IIAP‐SiPV; Kuwait Foundationfor the Advancement of Sciences, Grant/Award Number: P115‐15EE‐01

Copyright © 2018 John Wiley & Sons, Ltd. In this work, the ATOM (intrinsic a-Si:H/TiO x /low work function metal) structure is investigated to realize high-performance passivating electron-selective contacts for crystalline silicon solar cells. The absence of a highly doped Si region in this contact structure is meant to reduce the optoelectrical losses. We show that a low contact resistivity (ρ c ) can be obtained by the combined effect of a low work function metal, such as calcium (Φ 2.9 eV), and Fermi-level depinning in the metal-insulator-semiconductor contact structure (where in our case TiO x acts as the insulator on the intrinsic a-Si:H passivating layer). TiO x grown by ALD is effective to achieve not only a low ρ c but also good passivation properties. As an electron contact in silicon heterojunction solar cells, inserting interfacial TiO x at the i-a-Si:H/Ca interface significantly enhances the solar cell conversion efficiency. Consequently, the champion solar cell with the ATOM contact achieves a V OC of 711 mV, FF of 72.9%, J SC of 35.1 mA/cm 2 , and an efficiency of 18.2%. The achievement of a high V OC and reasonable FF without the need for a highly doped Si layer serves as a valuable proof of concept for future developments on passivating electron-selective contacts using this structure. ispartof: PROGRESS IN PHOTOVOLTAICS vol:26 issue:10 pages:835-845 status: published

Argon (Ar) and oxygen (O2) plasmas are performed on silicone adhesives to eliminate the negative influence of silicone on amorphous silicon (a-Si:H) surface passivation of wafers bonded to glass. Both the Ar and O2 plasmas lead to oxidation of the silicone surface, consisting in an increase of oxygen/carbon ratio, of degree of crosslinking, and of material density. The oxidized silicone is more resilient than pristine and does not interact with the a-Si:H passivation process, allowing for state-of-the-art surface passivation of wafers bonded to glass. Similarities between the modifications induced by the Ar and O2 plasmas on the silicone indicate the secondary role of the O2 radicals in the oxidation process. Moreover, amorphous/crystalline heterojunction interdigitated back contact solar cells (a-Si:H/c-Si HJ i-BC) are fabricated on freestanding and bonded wafers treated with Ar plasma. The devices show comparable open-circuit voltages of up to 675 mV, confirming at device level the efficacy of the treatment.

A parametric study of post-deposition hydrogen plasma treatment of intrinsic a:Si:H films is performed. We demonstrate a significant improvement in passivation of c-Si(100) promoting epitaxy after an in-situ hydrogen plasma treatment depending mainly on the pressure and slightly on the power. Plasma diagnostic indicates an increase of Hα* signal with high power and low pressure. However, our analysis reveals a better hydrogen incorporation with high pressure and a slight increase in monohydride with high power. Longer H2 plasma duration up to 50 s shows no detrimental effect on the passivation quality. Optimizing the in-situ H2 plasma treatment, high minority carrier lifetime over 15 ms was achieved after short thermal annealing. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)