Electronic Junction Control in a Nanotube-Semiconductor Schottky Junction Solar Cell

Abstract

We exploit the low density of electronic states in single wall carbon nanotubes to demonstrate active, electronic modulation of their Fermi level offset relative to n-type silicon in a nanotube-Si (metal-semiconductor) Schottky junction solar cell. Electronic modulation of the Fermi level offset, the junction interface dipole and a field developed across the depletion layer modifies the built-in potential in the device and its power generation characteristics. As produced (before modulation) devices exhibit ∼8.5% power conversion efficiency (PCE). With active modulation the PCE is continuously and reversibly changed from 4 to 11%.

Carbon nanotubes for organic/inorganic hybrid solar cells

“…nanometer thin SiOx insulator between the Si and metal, minority charge carriers will be transported through the insulating layer by CNT fibers [119]. By applying a series of doping and gating methods such as SOCl 2 treatment [116], ionic liquid electrolyte infiltration and electronic gating [120,121] as well as nitric acid doping [122], the power conversion efficiencies of the CNT-Si cells have been continuously pushed from initially about 1.3% to 13.8% (within the last several years.…”

Implementation of antireflection layers for improved efficiency of carbon nanotube–silicon heterojunction solar cells

“…Similar devices were also reported using the CNT deposition method of Wu [4] which involves vacuum filtration of CNT onto mixed cellulose ester (MCE) membranes which can then be removed by dissolution with acetone [13]. Application of a gate potential to alter electronic junction properties (via ionic liquid electrolyte) was reported to adjust efficiency between 4 and 11 % reversibly and dynamically, and this was interpreted to be due to the modulation of carbon nanotube Fermi level and improvement of the homogeneity of the silicon depletion region [14]. Even higher PCE solar cells (13.8 %) have been reported in which nanotubes were doped in situ by nitric acid (HNO 3 ), where a decrease of tube-tube resistance and shifting of Fermi level down into the valence band contributed to high efficiency [9].…”

Self-Organized Micro-Honeycomb Network Structure of Single-Walled Carbon Nanotubes for Photovoltaic Devices

“…Since then, this simple but efficient structure ignited great research interest worldwide. Wadhwa et al [3] used SWNTs "buckypaper" with SOCl2 ionic liquid and obtained the efficiency of 8%. SWNTs showed good performance but the fabrication process of SWNTs film included surfactant, sonication, vacuum filtration and liquid state doping chemicals which made the device life-time extremely short.…”