Investigation of thin film solar cells on CdS/CdTe base with different back contacts

Abstract

The peculiarities of photo-electric processes in thin film CdS/CdTe solar cells (SC) with different back electrodes (Cu/Au, ITO, Cu/ITO) havebeen studied. As it was established by capacitance – voltage (C-V) characteristics, the potential barrier heights for CdTe/Cu/Au and CdTe/ITO were 0.3 eV and 2.2 eV, respectively. The concentrations of charge carriers near back contact consisted 9⋅10²⁰ m⁻³ and 2⋅10²¹ m⁻³, respectively. A high carrier concentration and hi gh potential barrier of the ITO back contact caused the tunnel – recombination mechanism of the charge transport. The investigations of CdS/CdTe/ITO SC spectral photosensitivity testify a negative impact of the developed grain-boundary surface of the base layer on the processes of diffusion and separation of non-equilibrium currentcarriers generated by short-wave radiation. It is shown that the deposition of Cu nanolayer before the deposition of ITO films give stable efficiency 10% for bifacial CdS/CdTe solar cells.