**7. References**

108 Solar Cells – Thin-Film Technologies

 0.5 deg 3 deg Cu2 O CuO 0.5Cu2

O+0.5CuO

0123456

R (Å)

Fig. 20. Amplitudes |F(R)| obtained from the Fourier transformation of the EXAFS spectra of the Ti/CuO/Cu2O heterojunction at φ = 05 and 30 degrees and of the electrodeposited

Single phase polycrystalline Cu2O thin films on Ti substrate can be electrodeposited using an acetate bath in a potential range of 0 to -300 mV Vs SCE. Thin films are well adherent to the Ti substrate and uniform having grain size of ~1-2 m. Cu2O deposited in an acetate bath at the pH of 6.6 produces n-type photoconductivity in a PV applications. The n-type photoconductivity of the as-grown Cu2O thin film can be converted to p-type by annealing the films at 300 oC in air. Therefore, it is reasonable to believe that the origin of the n-type Cu2O is the oxygen ion vacancies created in the crystal lattice, and the conductivity-type conversion is due to the increment of the oxygen content in the lattice with annealing in air. Single phase polycrystalline CuO thin films can be prepared by annealing the electrodeposited Cu2O at 500 oC for 30 min in air. Films produce p-type photoresponse in a PEC. Well covered n-type Cu2O thin film can be electrodeposied on Ti/CuO electrode at -550 mV Vs the SCE in an acetate bath. Films consist of microcrystallites of about 1 m and are well adherent to the CuO. By depositing a suitable mettle grid on the Cu2O thin film, p-CuO/n-Cu2O heterojunction solar cell can be fabricated. The Ti*/*CuO*/*Cu2O*/*Au heterojunction solar cell results in Voc of 210 mV and Jsc of 310 μA. This initial stage performance can be enhanced by depositing very thin Cu2O films leading to minimize the resistance of the Cu2O and choosing better ohmic contact to the Cu2O. Best ohmic contact to the n-type Cu2O may be Al but not the Au. X-ray diffractions and the X-ray absorption spectra, using the synchrotron radiation, reveal that Cu2O and CuO are high quality semiconducting thin films (free of amorphous phases) but amorphous structure is

Prof. W. Siripala, Professor of Physics, Department of Physics, University of Kelaniya, Sri Lanka and Prof. M. Hidaka, Department of Fundamental Physics, Graduate School of

Cu2O and CuO thin films and the calculated one of (05Cu2O + 05CuO)

formed between CuO and Cu2O while Cu2O deposition on CuO.

0.00

0.05

0.10


**5. Conclusion** 

**6. Acknowledgment** 

0.15

0.20

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**6** 

**TCO-Si Based Heterojunction** 

*2Department of Applied Physics, Donghua University, Shanghai* 

*1SHU-Solar E PV Laboratory, Department of Physics, Shanghai University, Shanghai* 

It is a common viewpoint that the adscription of the PV research and industry in future has to be the lower cost and higher efficiency. However, those monocrystal as well as multicrystalline silicon wafer require very expensive processing techniques to produce low defect concentrations, and they are made by complicated wet chemical treatment, hightemperature furnace steps, and time-cost metallization. Thus, a high PV module cost exists for the first-generation technology. Recently, a strong motivation in R&D roadmap of PV cells has been put forward in thin film materials and heterojunction device fields. A large variety of possible and viable methods to manufacture low-cost solar cells are being investigated. Among these strategies, transparent conductive oxides (TCOs) and polycrystalline silicon thin films are promising for application of PV and challenging to

Converting solar energy into electricity provides a much-needed solution to the energy crisis in the world is facing today. Solar cells (SC) fabricated on the basis of semiconductor– insulator– semiconductor (SIS) structures are very promising because it is not necessary to obtain a p–n junction and the separation of the charge carriers generated by the solar radiation is realized by the electrical field at the insulator–semiconductor interface. Such SIS structures are obtained by the deposition of thin films of TCO on the oxidized semiconductor surface. One of the main advantages of SIS based SC is the elimination of high temperature diffusion process from the technological chain, the maximum temperature at the SIS structure fabrication by PVD/CVD being not higher than 450 ◦C. Besides that, the superficial layer of silicon wafer, where the electrical field is localized, is not affected by the impurity diffusion. The TCO films with the band gap in the order of 2.5–4.5 eV are transparent in the whole region of solar spectrum, especially in the blue and ultraviolet regions, which increase the photo response in comparison with the traditional SC. The TCO layer assists the collection of charge carriers and at the same time is an antireflection coating. The most utilized TCO layers are SnO2, In2O3 and their mixture ITO, as well as zinc oxide (ZnO). The efficiency of these kinds of devices can reach the value of more than 10% (Koida

Transparent conducting oxides (TCOs), such as ZnO, Al-doped ZnO or ITO (SnO2:In2O3), are an increasingly significant component in photovoltaic (PV) devices, where they act as electrodes, structural templates, and diffusion barriers, and their work function are

develop cheap TCOs and TCO/c-Si heterojunction cells.

**1. Introduction** 

et al., 2009).

**Photovoltaic Devices** 

Z.Q. Ma1 and B. He2

*P. R. China* 

