Solar cells on thin (≤150μm) multi-crystalline Si (mc-Si) substrates require diffusion lengths exceeding twice the substrate-thickness combined with an excellent rear-surface passivation in order to reach efficiencies above 16%. Moreover, thin substrates no longer allow the use of screenprinted Al for back-surface-field (BSF) and contact formation, due to excessive warping upon firing. Gettering originating from POCl3 emitter diffusion, is shown to enhance the bulk-quality to fulfill the first requirement. PECVD amorphous-Si (a-Si) layers, on the other hand, provide very low surface recombination rates. As a consequence, a POCl3 diffused front emitter, combined with a heterostructure a-Si / mc-Si rearside is suggested to overcome the several constraints present when shifting to the use of thinner substrates within a low-cost environment.