High-performance tandem silicon solar cells on F:SnO2
High-performance transparent conducting oxides (TCOs) have significance for optimising PV performance. The efficiency of the resulting solar cells is dependent particularly on achieving high light scattering, low resistivity and low absorption (via low free carrier absorption), in addition to suitable surface morphology for absorber growth quality. These properties have been targeted by systematic exploration of the Atmospheric Pressure Chemical Vapour Deposition (APCVD) growth parameters, in particularly the effect of the tin precursor to water ratio. Using the APCVD process F-doped SnO2 has been deposited on glass using monobutyl tin trichloride with trifluoro-acetic acid as the dopant source. Experiments established that an increased water to tin precursor ratio gave smaller surface features, along with increased electrical mobility and optical transmittance at high reactant ratios. Samples were then used in manufacture of thin film solar cells, which showed enhanced performance, in comparison to commercially available TCO CVD coated glasses, with high quantum efficiency yield. In particular, high water to tin precursor ratios led to much improved open circuit voltages, fill factors and high current densities within the cells. Tandem cells with efficiencies of 10.75% were achieved, which were higher than those produced concurrently using commercially available TCO both on-line 9.50% and off-line 10.20%. (C) 2013 Elsevier B.V. All rights reserved.