The structural, composition and optical absorption properties of Cd1−xZnxS (CdZnS) thin films fabricated by the reactive diffusion of Zn in CdS have been investigated. These ternary compounds were characterized by x-ray diffraction (XRD), energy dispersive x-ray fluorescence and optical absorption measurements. It is established that thermal annealing of Zn/CdS structure at temperature (400 °C) lower than the melting point of Zn (418 °C) results in the concentration distribution of Zn in CdS film described by an erfc-curve (D = 5 × 10−14 cm2 s−1) and characterizing the free impurity diffusion from a constant source. In contrast to this, the concentration profile of Zn in CdS film at higher annealing temperature (570 °C) is not described by the erfc-curve and shows a nearly stepped form, which is characteristic of reactive diffusion. XRD patterns of Zn/CdS structures annealed at 570 °C showed diffraction peaks of ternary CdZnS compounds. Analysis of the absorption spectrum of such films indicates formation of CdZnS composition with the largest value of energy band gap up to 2.64 eV, exceeding the band gap of CdS (2.43 eV). It is concluded that interdiffusion in Zn/CdS structures at temperatures exceeding the melting point of Zn was accompanied by formation of Cd1−xZnxS ternary compounds. The band gap of this variable band structure changes from 2.64 eV in the near surface region to 2.43 eV (CdS) in the inner region of the film.

No abstract

No abstract

No abstract

In this paper, the photovoltaic characteristics of bulk heterojunction solar cells employing an eutectic gallium-indium (EGaIn) alloy as a top metal contact which was coated by a simple and inexpensive brush-painting was investigated. The overall solar cell fabrication procedure was vacuum-free. As references, regular organic bulk heterojunction solar cells employing thermally evaporated Aluminum as a top metal contact were also fabricated. Inserting the ZnO layer between the active layer and the cathode electrodes (Al and EGaIn) improved the photovoltaic performance of the herein investigated devices. The power conversion efficiencies with and without EGaIn top electrodes were rather comparable. Hence, we have shown that the EGaIn, which is liquid at room temperature, can be used as a cathode. It allows an easy and rapid device fabrication that can be implemented through a vacuum free process.