Graphene oxide as a p-dopant and an anti-reflection coating layer, in graphene/silicon solar cells

Abstract

It is shown that coating graphene-silicon (Gr/Si) Schottky junction based solar cells with graphene oxide (GO) improves the power conversion efficiency (PCE) of the cells, while demonstrating unprecedented device stability. The PCE has been shown to be increased to 10.6% (at incident radiation of 100 mW cm(-2)) for the Gr/Si solar cell with an optimal GO coating thickness compared to 3.6% for a bare/uncoated Gr/Si solar cell. The p-doping of graphene by the GO, which also serves as an antireflection coating (ARC) has been shown to be a main contributing factor to the enhanced PCE. A simple spin coating process has been used to apply GO with thickness commensurate with an anti-refection coating (ARC) and indicates the suitability of the developed methodology for large-scale solar cell assembly.

Modeling and Design of a New Flexible Graphene-on-Silicon Schottky Junction Solar Cell

“…The optimum refractive index of the ARC layer nARC is the geometric mean of the refractive index of silicon and air [39]. Since the solar energy intensity is maximum at about 0.55 μm [40] and the silicon refractive index at that wavelength is 4.1 [35], the optimum value of nARC is 2.0, which is very close to the refractive index of a GO layer with a thickness of <100 nm [31]. Thus, a GO layer can be used as ARC.…”

“…For V OS , J SC , and FF the differences are <0.015 V, <5 mA/cm 2 , and ≤5%, respectively. The second solar cell simulated by our model is that reported in [31]. It is a cell based on a monolayer graphene/n-Si Schottky junction that has been experimentally studied with and without a GO layer with a thickness of 100 nm on the graphene sheet.…”

“…D p was expressed as kT (µ p /q), and the analytical expression in [37] was used for the hole mobility µ p . Data in [31] were used to estimate R S , the reflectivity R(λ), and the wavelength-dependent transmittance of graphene, GO, and SiO 2 . where Vmax and Jmax are the voltage and the current density at the maximum-power operating point, respectively, i.e., the point of the I-V characteristics of the solar cell where the generated electric power P = V I is maximum.…”

“…Dp was expressed as kT (μp/q), and the analytical expression in [37] was used for the hole mobility μp. Data in [31] were used to estimate RS, the reflectivity R(λ), and the wavelengthdependent transmittance of graphene, GO, and SiO2. The first device considered for the validation of our model is a solar cell made by a monolayer graphene/ultrathin silicon Schottky junction [25].…”

“…The graphene oxide film induces the p-doping of the graphene [31] with a consequent increase of both the work function and the conductivity of the graphene sheet. In addition, the GO film acts as an anti-reflection coating layer, as explained in Section 3.…”