Integration of a-IGZO Thin-Film Transistor and Crystalline-Si Interdigitated Back Contact Photovoltaic Cell With 3D Stacking Structure as Self-Powered Solar Switch

Abstract

Abstract —In this letter, a Ta 2 O 5 /a-IGZO thin film transis-tor (TFT) was directly stacked on a crystalline-Si interdigitatedback contact (IBC) photovoltaic (PV) cell to create a self-poweredsolar switch. The a-IGZO TFT and IBC PV cell were integratedinto a single chip without an external circuit. This device exhibitsswitching property induced by illumination. The results showthat it can be switched even under a low solar illumination of300 W/m 2 due to the low threshold voltage of the a-IGZO TFT(0.25 V). The ON / OFF current contrast ratio was measured tobe ∼ 20 under 1-sun illumination. The fabrication process andcharacteristics of this device make it suitable and practicable foruse as a self-powered solar switch. Index Terms —Interdigitated back contact (IBC), a-IGZO,self-powered device. I. I NTRODUCTION O XIDE semiconductor-based thin-film transistors (TFTs)have made impressive progress for application in trans-parent electronics and displays. Among them, amorphousindium gallium zinc oxide (a-IGZO) is considered one of themost promising materials as the channel layer for TFTs dueto its good carrier mobility, which is considerably higher thanthat of a-Si:H TFTs [1], [2].Recently, self-powered devices which could function wellwithout the external power unit have attracted a lot of atten-tion, especially for the issue of energy shortage. Yang et al.fabricated a self-powered device by connecting a single fibernanowire hybrid-structured microbial fuel cell (MFC) witha single CdS nanowire photosensor in series [3]. However,their MFC was separated from the photosensor by an externalcircuit, which was not easily to integrate. Shen et al. fabri-cated CIGS PV cells and microcrystalline-Si TFTs as self-powered electronics on the same plane [4]. Their group alsodemonstrated a hybrid Si-based thin film PV cell/transistor