The highly conductive and textured ZnO films have been grown by metalorganic chemical vapor deposition using diethylzinc and H2O as reactant gases. The B2H6 gas has also been successfully used as an n‐type dopant gas to obtain highly conductive ZnO with a sheet resistivity for 2‐μm‐thick film as low as 10 Ω/⧠ at the very low temperature of 150 °C. It was found that the crystal orientation and grain structure change with B2H6 flow rate. The decreasing of the film transmittance due to the free‐carrier absorption in the wavelength region above 1000 nm was observed and it seems that the impurity scattering was the dominant interaction during this process. The shift of the absorption edge due to band filling was also observed as the B2H6 flow rate was increased.

Electrical and optical properties of boron‐doped ZnO thin films for solar cells grown by metalorganic chemical vapor deposition

Absorption losses at a nanorough silver back reflector of a solar cell were measured with high accuracy by photothermal deflection spectroscopy. Roughness was characterized by atomic force microscopy. The observed increase of absorption, compared to the smooth silver, was explained by the surface plasmon absorption. Two series of silver back reflectors (one covered with thin ZnO layer) were investigated and their absorption related to surface morphology.

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Absorption loss at nanorough silver back reflector of thin-film silicon solar cells

This chapter covers the current use and challenges of thin-film silicon solar cells, including conductivities and doping, the properties of microcrystalline silicon (the role of the internal electric field, shunts, series resistance problems, light trapping), tandem and multijunction solar cells (a-Si:H/a-Si:H tandems, triple-junction amorphous cells, microcrystalline–amorphous or “micromorph” tandems), module production (deposition of thin-film layers, substrate materials, laser scribing, cell interconnection, and module encapsulation), and module performance.

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Thin-Film Silicon Solar Cells

An amorphous silicon solar cell on a periodic nanocone back reflector with a high 9.7% initial conversion efficiency is presented. The optimized back-reflector morphology provides powerful light trapping and enables excellent electrical cell performance. Up-scaling to industrial production of large-area modules should be possible using nanoimprint lithography.

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High‐Efficiency Amorphous Silicon Solar Cell on a Periodic Nanocone Back Reflector

Effect of surface roughness of ZnO:Al films on light scattering in hydrogenated amorphous silicon solar cells

The role of back reflectors in enhancing the absorption of weakly absorbing, long‐wavelength light has been investigated as applied to amorphous silicon alloy solar cells. The reflectance and scattering properties of various types of back reflectors have been studied. The performance of p‐i‐n amorphous silicon alloy solar cells deposited on different back reflectors has been analyzed. The studies elucidate the role of back reflectors in improving the short‐circuit current density and thereby the efficiency of the cell.

A. Banerjee

Papers

Study of back reflectors for amorphous silicon alloy solar cell application