Abstract
In this work, a new structure ITO/n-ZnO/n-CdS/p-CuO:Co/Ag for solar cell was prepared on a glass/ITO substrate. The RF sputtering was used to deposit the window layer (n-ZnO) at different time periods in order to reach various thickness of this film. The n-CdS thin films were synthesized by sol-gel technique to reduce the energy bands. The buffer layer (p-CuO:Co) was sputtered at 200 W, under 30% of oxygen. Then, the electrode (Ag) with a thickness of 100 nm was deposited by thermal evaporation under a pressure of 10−5 mbar. The photovoltaic activity results obtained from this structure showed that the above method is more relevant to achieve such structure. The electrical properties of this structure were investigated using the current-voltage (I-V) and AC impedance complex measurements. The values of open circuit voltage (Voc), short-circuit current (Jsc), and fill factor (FF) are 0.46 V, 4.1 mA cm−2, and 30%, respectively. The analysis of complex impedance measurements was very useful to investigate the electrical behavior of n-ZnO/n-CdS and n-CdS/p-CuO:Co interfaces. The impedance data are presented in the Nyquist and Bode plots at different thicknesses of the n-ZnO films. An equivalent circuit was used to analyze and to fit the experimental data. The validity of these fitting results is further supported by the extrapolation and the deconvolution of both process of the diffusion and recombination processes at the n-ZnO/n-CdS and n-CdS/p-CuO:Co interfaces, respectively. Our finding could provide an efficient method for fabricating a new configuration for improving the efficiency of inorganic ZnO/CuO solar cells as well as a useful approach for the analysis of complex impedance measurements. Further works are in progress in order to better improve the conversion efficiency.
Highlights
During the last decades, solar cell technology has attracted the intention of many researchers. e best is to improve the efficiency of solar cells and to prepare devices at a low cost. us, it is sought to replace the silicon and germanium by low-cost semiconductors
We note that the ZnO films are highly transparent in the visible range with an average transmittance value of almost 90%. ereby, the presence of interference fringes in the transmission spectra indicates that the thin films of ZnO are homogeneous with better optical quality and the bond gap is almost constant around Eg 3.28 Energy level (eV) (Table 1), which is in good agreement with previous works
The alignment between the different bands is well suited for the separation of pairs (e−, e+), which facilitates the process of separation of charges. e band gap for CdS moves between the different components facilitating the efficient transport of electrons from the conduction band from CdS to ZnO to indium tin oxide (ITO) electrodes and transport of holes in the valence band of Cuprous oxide (CuO):Co films to the Ag electrodes [10]
Summary
Solar cell technology has attracted the intention of many researchers. e best is to improve the efficiency of solar cells and to prepare devices at a low cost. us, it is sought to replace the silicon and germanium by low-cost semiconductors. E best is to improve the efficiency of solar cells and to prepare devices at a low cost. Cuprous oxide (CuO) is a nontoxic p-type semiconductor material with abundant soil, with optical band gap around 1, 5 eV [1, 2]; cuprous oxide can act as a light absorber in heterojunction or tandem solar cells. Copper-based oxides have promising electrical, optical, and manufacturing characteristics that establish this family of materials as well suited for semiconductor P. For this reason, CuO thin films can be obtained by different techniques such as sol-gel [3], thermal evaporation [4], electrodeposition [5], and radiofrequency (RF) sputtering technique [6]. A low conversion efficiency was obtained close to 0.01%
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