Fishnet metastructure for efficiency enhancement of a thin film solar cell

Abstract

We propose embedment of a fishnet metastructure in the back passivation layer for enhancing the efficiency of hydrogenated amorphous silicon (a-Si:H) thin film solar cells. Incident light excites a plasmon resonance that results in frequency dependent effective impedance for the embedding layer so that the input impedance satisfies impedance matching condition. Reflection is very low under this condition. A planar 20 nm-thick fishnet structure is embedded in the back passivation layer of the solar cell to enhance light absorption near the bandgap of a-Si:H. This enhancement remains over a wide range of incident angles. Detailed electromagnetic modeling of the absorption in different layers of the solar cell is performed. Only absorption in the a-Si:H is included in computing the photocurrent generation. 64% of the total absorbed energy at resonance is in the silicon layer and this absorption is uniformly distributed inside the silicon. Based on the enhancement of photocurrent density near the bandgap of a-Si:H, we obtained 14.8% enhancement in total short circuit current at normal incidence and the estimated PV efficiency of the solar cell with the fishnet is 7.43% at normal incidence compared to 6.36% without fishnet. The fishnet can be tuned to provide absorption enhancement at any desired frequency where the intrinsic absorption of the semiconductor is low.

Nanoplasmonics: a frontier of photovoltaic solar cells

“…The application of metamaterials in PV has also been proposed [121 -125] . Theoretical work has been proposed and demonstrated on embedding a planar 20 nm-thick fi shnet metamaterial structure in the rear passivation layer of a-Si thin-fi lm solar cells for enhancing the effi ciency [126] . By matching the input impedance to reduce the refl ection and exciting the plasmon resonance of the metamaterial, light absorption near the bandgap of the a-Si active layer was enhanced by 12 times at the normal incidence.…”

Photonic nanometer scale metamaterials and nanoporous thermoelectric materials for enhancement of hybrid photovoltaic thermoelectric devices

“…6 The plasmon resonance strongly depends on the geometry, material properties of the fishnet and the embedding layers. Therefore, the geometry and material properties of the fishnet are important design parameters in determining the resonance for embedding fishnet into the given layers of PV-TE hybrid systems.…”

“…There are several techniques adapted to absorb more solar radiation. In common, the SSA with low reflectance in the wavelength range from 600 nm to 1600 nm can be coated on the hot side of the TE generator of the hybrid system to absorb residual sunlight transmitted through the solar cell 6 . Apart from absorbing more solar radiation, system can use functionally graded material (FGM) as a heat sink (cold side) of the TE generator to make higher temperature difference between the hot and cold side of the TE generator 7 .…”

Solar cells based on particulate structure of active layer: Investigation of light absorption by an ordered system of spherical submicron silicon particles

“…To attain this end plasmonic and diffractive nanostructures, down-converting particles, surface texturing, nanohole patterning etc. are widely studied [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. In this investigation we examine the possibility to enhance light absorption by particulate active layer.…”