Fabrication of Cu2O Homojunction Solar Cell

Abstract

Cu2O, a natural p-type semiconductor with a narrow band gap of 2 eV, is an attractive material for photovoltaic devices because of its nontoxicity and low production cost. In early investigations, p-Cu2O/metal Schottky junctions or p-Cu2O/n-type semiconductor heterojunctions were reported due to the absence of n-Cu2O. Cu2O homojunction attracts much attention with the invention of possibility of growth of the n-type Cu2O in 1986 by the method of electrodeposition. Recently, p-n Cu2O homojunction solar cells were fabricated by the electrochemical deposition of p-Cu2O layer, followed by n-Cu2O layer, in which the highest cell efficiency was reported to be 1.06%. However, performances of reported Cu2O homojunction solar cells are poor compared to the theoretical efficiency of 12%. It has been understood that one of the options to improve the Cu2O homojunction solar cell would be the formation of p- layer on top of the n-layer. In this study, the possibility of consecutive electrodeposition of p-Cu2O layer on n-Cu2O layer was examined to fabricate n-p Cu2O homojunction , which has not been reported earlier. The electrodeposition of Cu2O was studied in a three electrode electrochemical cell, under a potentiostatic condition of -200 mV Vs Ag/AgCl at 55o C. n-Cu2O films were cathodically deposited on Ti substrates in an aqueous solution of 0.1 M sodium acetate and 0.01 M cupric acetate for 60 min. Prior to the deposition of n-Cu2O, the solutions were adjusted to a pH 6.12 of using HCl. In order to fabricate an n-p homojunction, the electrodeposition of p-Cu2O was carried out on top of the previously deposited n-Cu2O layer. p-Cu2O was electrodeposited in an aqueous solution of 0.1 M sodium acetate and 0.001 M cupric acetate for 40 min. n-p Cu2O homojunction was characterized by using dark and light current-voltage measurements and spectral response measurements in a PEC containing 0.1 M sodium acetate solution. Dark and light current-voltage measurements and spectral response measurements reveal that the photoactivity of the device enhances due to the formation of n-p Cu2O homojunction. In conclusion, the study reveals the possibility of fabrication of n-p Cu2O homojunction by electrodeposition.