Experimental and theoretical studies of Cu 2O solar cells

Abstract

Extensive studies of Cu 2O Schottky barrier solar cells have been conducted. Schottky barrier devices based on metals characterized by a wide range of work functions have been investigated. Cell characterization includes electro-optical studies, thermodynamic considerations concerning interface stability and depth-concentration profiles. Cu/Cu 2O cells were develope that exhibited active-area air mass 1 values of photocurrent and efficiency of 8.5 mA cm −2 and 1.8% respectively. A detailed photon and carrier loss analysis conducted for Cu/Cu 2O cells is used to project the ultimate values of the photocurrent for Cu 2O cells to be 12 – 14 mA cm −2. Thermodynamic considerations indicate that thallium is the only metal which can be combined with Cu 2O to yield an adequate efficiency. However, Tl/Cu 2O Schottky barrier cells exhibit properties similar to Cu/Cu 2O devices. Depth-concentration profiles show that, although no TlO bonding exists in the interfacial region, the region is copper rich. It is concluded that the oxygen deficiency occurs because of preferential sputtering of oxygen during the thallium deposition process. As a result of these Cu 2O Schottky barrier studies, it is concluded that significant improvements in the efficiency of Cu 2O solar cells can be achieved only with a homojunction structure. Thus, an approach to doping Cu 2O n type must be developed in order for the potential of this material for low cost photovoltaics to be realized.