Role of front and back contacts in the performance of TiO2/CuO heterojunction solar cells

Abstract

In this work, the effects of front and back contact work functions on the performance of a TiO2/CuO heterojunction solar cell were studied using numerical simulations. Our findings revealed a high device efficiency of ∼ 18 %, and VOC ∼ 0.83 V can be obtained when the work function values of the front transparent conducting oxide (TCO) electrode are below 4.6 eV, provided the metal at the back contact has a work function above 5.1 eV. The underlying cause of this observation can be explained by the carrier concentration profiles across the device, which indicate the formation of a higher potential barrier for the majority carriers at front contact/emitter interface, for front contact work functions (ϕFC) above 4.6 eV, due to which relatively lesser electrons are collected at the electrode. Compared to this, a lower potential barrier for the majority carriers develops when ϕFC < 4.6 eV, implying higher electron collection at the front electrode. At the absorber/back contact interface, formation of a higher potential barrier for the holes impedes their collection when the metal back contact with work function values below 5.1 eV.