Question

Silicon solar cells vs. thin-film solar cells Compare silicon solar cells with thin-film solar cells in the following aspects: (1) device structure; (2) working principle; (3) efficiency; and (4) cost. Need informative answer for my clear understandings.

Answer 1

Answer Part 1

Solar cells are structured in layers with different functions. The working principle is the same as in semiconductors.

The main part of a silicon (Si) solar cell is formed by two differently doped (n- and p-) silicon layers. A physical barrier is created between them along the p-/n- junction, with electrons and holes diffusing into regions of lower concentration.

Whereas Thin film solar cells are actually an umbrella term describing a wide variety of silicon photo voltaic device structures. Thin film solar cells are distinguished from traditional silicon solar cells that are composed of ～0.3-mm-thick wafers or sheets of silicon. The common defining feature of a thin silicon solar cell is a relatively thin (<0.1-mm) active layer or film of silicon formed on, or attached to, a passive supporting substrate.

Answer Part 2

Working principle for silicon solar cells is as follows :

To be able to channel electrons and holes and generate electric power, metal contacts need to be printed onto the front and rear side. Generally, a full aluminium or silver layer is screen printed onto the rear. A thin grid forms the front contact keeping the impact on light entering the silicon cells as low as possible.To reduce light reflection, a thin film of silicon nitride or titanium dioxide is coated onto the surface.

Whereas in the case of Thin - film solar cells the light trapping effect is the main reason for their high efficiency which can offset the relatively weak absorption near-band-gap energy photons by increasing the optical path length of light within the solar cell structure. The backside of the solar cell with a grooved, blazed, textured, or otherwise roughened surface is made reflective changing the refractive index, or by coating with a reflective material such as a metal.

In a silicon solar cell, this surface is the backside of the solar cell itself, but in a thin film solar cell formed on a substrate, the reflective backside mirror is situated at the interface between the silicon film and the substrate.

Answer Part 3

Efficiency of Solar Cells

Solar cell efficiencies vary from 6% for amorphous silicon-based solar cells to 44.0% with multiple-junction production cells and 44.4% with multiple dies assembled into a hybrid package. Solar cell energy conversion efficiencies for commercially available multi crystalline Si solar cells are around 14–19%.

Whereas thin-film solar cells have reached 20 percent efficiency in laboratory settings and 14 percent efficiency in the field, making CIGS a leader among alternative cell materials and a promising semiconducting material in thin-film technologies.

Answer Part 4

Cost of Solar Cells Comparison

Most solar cells are made from silicon—the same semiconductor material that is at the heart of computers. The cells are expensive to produce because it takes a great deal of energy to purify the silicon. ... “The semiconductor industry makes minutely patterned silicon .Whereas thin film solar panels are less efficient, require more space, but are more flexible and can be mounted easily on roofing tiles or shingles. These are the least expensive solar panels available at a price of about $2-$4 per watt average.