Characterisation of LPE thin film silicon on low cost silicon substrates [solar cells]

Thin Si layers of 8-30 μm were grown by LPE on upgraded metallurgical (UMG) multicrystalline Si substrates. A melt back step just before the growth process circumvented the additional supply of Si to the melt. Solar cells, realized by using a simple screenprinting process, reached efficiencies up to η=6% (FF=74.1%, J_SC=14.7 mA/cm², V_OC=551 mV) without antireflection coating. The influence of impurity diffusion from the substrate into the active layer and the impurity incorporation from the In solution during the growth process have been studied (e.g. by SIMS). Using Secco etching, LBIC and spectral response measurements it could be shown that the local I_sc is not limited by impurities and further increases in l_sc could be achieved by growing thicker epilayers. The results of the investigations underline the good crystal quality of the epilayers on UMG Si substrates and enables the further increase of the efficiency