Copper oxide based low cost thin film solar cells

Copper oxide is one of the earliest semiconductor materials investigated for solar cells in the early 1900´s before silicon cells became widespread. It is environmentally friendly, nontoxic and furthermore copper is an abundant metal. In spite of having low power conversion efficiencies when compared to theoretical values, there is much scope to further improve the efficiency. Copper oxide exists in two stable forms namely, CuO and Cu₂O with a direct band gap in each case. The band gap can be tuned between 1.6 eV (CuO) to 2.3 eV (Cu₂O). In the present work, semiconducting copper oxide have been deposited on glass and (100) silicon substrates by using radio frequency (RF) sputtering technique with a CuO target in argon ambient. After deposition, thermal annealing treatment was carried out at different temperatures ranging from 300°C to 550°C in rapid thermal annealing (RTA) system. The structural properties and composition of the deposited films have been studied by using X-ray diffraction and X-ray photoelectron spectroscopy analysis. Optical and electrical properties were studied by using UV-Vis spectrophotometer and current-voltage (I-V) characteristics. The band gap of ~1.6 eV was obtained for sputtered CuO oxide after annealing at 300°C. Hetero-junction solar cells was fabricated using p-type CuO and n-type Si(100) substrates. The I-V characteristics of hetero-junction solar cell under sunlight of air mass 1.5 and 100 mW/cm² illumination shows open circuit voltage of ~380 mV and short-circuit current of ~ 1 mA/cm².