Elaboration and characterization of CuInSe2 thin films using one-step electrodeposition method on silicon substrate for photovoltaic application

Bifacial solar cells combining a heterojunction cell on the upper side and crystalline silicon (c-Si) homojunction on the backside are very interesting devices to a more efficient use of the solar radiation. Cu(In,Ga)Se2(n)/c-Si(p)/c-Si(n+) or CuInSe2(n)/c-Si(p)/c-Si(n+) are very attractive heterojunctions to reach this target. In this work, a novel attempt has been made to grow CuInSe2 thin films on p-Si (100) substrate using one-step electrodeposition route with galvanostatic mode. The as-deposited samples were amorphous by nature which implies a rapid thermal annealing step. The effect of annealing temperature on the structural, morphological, optical and electrical properties of the fabricated hetero-structure CuInSe2/c-Si (100) was investigated by x-ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy (EDS) and UV–visible spectroscopy. XRD indicates that CuInSe2 films having single phase chalcopyrite with tetragonal crystal structure are obtained at 350 °C. Values of energy band gap of films at various annealing temperature were estimated to be in the range 0.94–1.01 eV. The optical parameters such as refractive index n(λ) and extinction coefficient k(λ) were estimated using an appropriate optical model. The AM1.5 current density–voltage characteristic of the fabricated Al/CuInSe2/c-Si (100) hetero-junction solar cell exhibits a short-circuit current density J sc of 4.06 mA cm−2, an open circuit voltage V oc of 0.28 V, a fill factor FF of 36.72% and a solar conversion efficiency η of 0.41%.