Asman Tamang

Light-Trapping and Interface Morphologies of Amorphous Silicon Solar Cells on Multiscale Surface Textured Substrates

The short circuit current and quantum efficiency of silicon thin-film solar cells can be increased by using multiscale surface textures consisting of micro- and nanoscale textures. Adding microtextures to the already existing nanosurface textures leads to an increase of the short circuit current from 15.5 mA/cm2 to almost 17 mA/cm2 for thin amorphous silicon solar cells. To gain insights into the light-trapping properties, finite difference time domain simulations were carried out using realistic interface morphologies. The simulations reveal that the gain of the short circuit current is caused by an increased effective thickness of the solar cell and the scattering properties of the microtextured back reflector. The thickness of the solar cells is increased by the growth of the silicon p-i-n diode on the microtextured surface. The influence of the nanoscale and multiscale surface textures on the quantum efficiency and short circuit current will be discussed.

Enhanced photon management in silicon thin film solar cells with different front and back interface texture.

Light trapping and photon management of silicon thin film solar cells can be improved by a separate optimization of the front and back contact textures. A separate optimization of the front and back contact textures is investigated by optical simulations taking realistic device geometries into consideration. The optical simulations are confirmed by experimentally realized 1 μm thick microcrystalline silicon solar cells. The different front and back contact textures lead to an enhancement of the short circuit current by 1.2 mA/cm2 resulting in a total short circuit current of 23.65 mA/cm2 and an energy conversion efficiency of 8.35%.

Zinc oxide nanowire arrays for silicon core/shell solar cells.

The optics of core / shell nanowire solar cells was investigated. The optical wave propagation was studied by finite difference time domain simulations using realistic interface morphologies. The interface morphologies were determined by a 3D surface coverage algorithm, which provides a realistic film formation of amorphous silicon films on zinc oxide nanowire arrays. The influence of the nanowire dimensions on the interface morphology and light trapping was investigated and optimal dimensions of the zinc oxide nanowire were derived.

Hybrid ZnO nanowire/a-Si:H thin-film radial junction solar cells using nanoparticle front contacts

Hydrothermally synthesized disordered ZnO nanowires were conformally coated with a-Si:H thin-films to fabricate three dimensional hybrid nanowire/thin-film structures. The a-Si:H layer formed a radial junction p-i-n diode solar cell around the ZnO nanowire. The cylindrical hybrid solar cells enhanced light scattering throughout the UV-visible-NIR spectrum (300 nm–800 nm) resulting in a 22% increase in short-circuit current density compared to the reference planar p-i-n device. A fill factor of 69% and a total power conversion efficiency of 6.5% were achieved with the hybrid nanowire solar cells using a spin-on indium tin oxide nanoparticle suspension as the top contact.