Highly transparent and conductive oxide-metal-oxide electrodes optimized at the percolation thickness of AgOx for transparent silicon thin-film solar cells

Abstract

Highly transparent and conductive oxide-metal-oxide (OMO) electrodes comprising aluminum-doped zinc-oxide (AZO) and ultrathin Ag or oxygen (O2)-doped Ag (AgOx) metal layers were fabricated for use in thin-film silicon solar cells. The surface morphologies of the metal layers and the transparencies and conductivities of OMO electrodes were investigated near the percolation thickness values of the metal layers. The percolation metal thickness, which means the metal layer is morphologically continuous, could be used to optimize the transparent OMO electrode. Additionally, thin Ag-based OMO (AgOx OMO) with superior performance could be fabricated by adding O2. The optimized AgOx OMO electrodes yielded the highest average transmittance (Tavg) of 93.5% and the lowest average optical loss (OLavg) of 1.01% within 500–800 nm at the percolation thickness of ~6 nm, thus, maintaining low conductivity. These outcomes were superior to the responses of the percolated Ag OMO (Tavg = 87.2%; OLavg = 1.01%). Using the OMO structure at the rear electrode, transparent hydrogenated amorphous silicon thin-film solar was fabricated for building integrated photovoltaic windows. The best figure-of-merit (FOM; equal to the product of Tavg and efficiency η) values of the OMO-based transparent solar cells could be obtained for percolated OMO structures. The cells using AgOx OMO (AgOx cells) performed better than the Ag cells; the best FOMs of AgOx and Ag cells were 140.8 (Tavg = 27.8%; η = 5.51%) and 104.6% (Tavg = 18.9%; η = 5.54%), respectively. These results could contribute to the development of high-performance transparent solar cells or optoelectronic devices.