The current trend in silicon photovoltaics towards high-quality thin mono-crystalline silicon substrates makes the accurate representation of surface recombination of utmost importance. It has been shown by several authors that an effective way to study detrimental defects in silicon wafers is by means of temperature and injection dependent lifetime spectroscopy (TIDLS) coupled with the Shockley-Read-Hall recombination model. Given its high sensitivity this is an excellent technique to study high lifetime substrates. However, a thorough evaluation of the surface recombination velocity (SRV) dependence on injection level and temperature is vital to the extrapolation of meaningful results regarding the defects contained in the bulk of the material. Here, we present a TIDLS study of a-Si:H(i), a-Si:H(n) and a-Si:H(p) deposited on «-type low-resistivity FZ substrates. We evaluate the impact of every dielectric layer on the total SRV temperature- and injection dependence while demonstrating its fundamental role in τ eff behavior of high-quality Si substrate.