Several thin-film solar cell technologies require light-trapping schemes that are predominantly based on depositing the solar cells on rough surfaces. While this approach efficiently increases the density of photo-generated carriers, open-circuit voltage and fill factor generally decrease. Substrates that decouple the growth interface from the light-scattering interface were previously proposed as a solution to this dilemma, and proof-of-concepts were demonstrated in thin film-silicon solar cells. In this contribution, we review as an introduction the problematic of rough versus smooth interface for n-i-p single-junction lc-Si:H cells. Then, the benefits of the newly developed substrate that decouples the growth and scattering interfaces are investigated in n-i-p triple-junction a-Si:H/lc-Si:H/lc-Si:H solar cells for the first time. Conversion efficiencies of 13.7% (initial) and 12.5% (stabilized) are obtained, which are among the highest ever reported for such devices.