Passivation of n-type silicon (111) surfaces by the attachment of charged molecules

With the drive for ever more efficient photovoltaics, the passivating layer becomes of greater importance. Currently, two main passivating mechanisms have been widely investigated; removal of surface states by organic layers and charging of surfaces to invert the surface bands. Our paper aims to increase the knowledge of this area by combining the removal of surface states with charging, in an attempt to build ever more efficient passivation layers. It was found that upon immersion in base, the recombination lifetime significantly improved from around 8 μs to over 30 μs, due to a negative monolayer surface charge. As the charge is further from the silicon surface, both the recombination lifetime and surface photovoltage (SPV) decrease. This in turn indicates a reduction in the surface electron concentration. Once the surface charge is neutralized, both the recombination lifetime and SPV return to their starting value.