There are many different types of solar cells. However, the most common and commercially available types are amorphous, polycrystalline, and monocrystalline cells; which derive their names from the nature of the silicon used to create their substrates. The conversion efficiency of a PV panel  (see the table below) and its cost will depend on the nature of the silicon used to manufacture the panel's solar cells.

Silicon Composition
Efficiency
Commercial Panels*
Known Max
Efficiency*
Amorphous Silicon
6
12.5
Polycrystalline Silicon
9.5-15.3
20.4
Monocrystalline Silicon
13.3-15.9
25
   *Efficiency (%) of Silicon Cells as measured at STC

Solar cells are tested at Standard Test Conditions (STC).  Incident sunlight of 1,000 W/m2 and a cell temperature of 25oC are two of the standard conditions.  You can read more about the effect of environmental factors and weather on PV output, at the Weather & Local Environment page.

Monocrystalline solar cells are manufactured from crystals of very pure silicon. A crystal is grown in a complex process to produce a long rod (also called "ingot"). The rod is sliced into 0.2 to 0.4 mm thick discs or wafers which are then processed into individual cells. These are wired together to create a solar panel. Under standard conditions, their conversion efficiency is much the same as those of  polycrystalline cells. Monocrystalline panels are noted, however, for their quality and are often used where high reliability is needed. Monocrystalline solar cells (and polycrystalline cells) experience a significant reduction in output at elevated cell temperatures. In Queensland, panels can often operate at a temperature of  50oC which is well above the 25oC used for the standard test conditions. As a result a reduction of between 12% and 15% in output can be expected on a bright sunny day and this needs to be factored into a project.

Solar panels made with polycrystalline cells (also called multicrystalline cells) are a bit cheaper and generally, slightly less efficient than those made up of monocrystalline cells.  The silicon is not grown as a single cell but rather as a block of crystals. These blocks are then sliced into wafers to produce individual solar cells. If you look closely at a polycrystalline panel, you will notice a shattered glass-like look to the cells - this an indication of the many crystals making up each cell. Polycrystalline cells have an even higher temperature derating factor than monocrystalline cells.

A thin layer of silicon is deposited on a base material such as metal or glass to create an amorphous solar panel. The silicon has no regular crystalline stucture.  The manufacturing process is reasonably  straightforward which results in relatively cheap panels. Amorphous solar cells are, however, only about half as efficient as polycrystalline and monocrystalline cells. Thus, in order to get the same electrical output as the crystalline cells, it is necessary to have twice the area of amorphus panels. This could  be a problem when space availability is limited.  Amorphous cells do not suffer reduced output  with increased cell temperature (i.e. temperature de-rating). 

A number of different types of solar cell types are used at the various University of Queenland PV sites. The table below provides a summary for the main installations at each site: 

Manufacturer
Model
Site
Type
Wp
Efficiency at STC
Schott
POLY 235
MBRS
Polycrystalline
235W
14.04%
Coenergy
P170M
Gatton
Monocrystalline
170W
13.30%
Trina
TSM-240PC05
St Lucia
Polycrystalline
240W
14.70%
Kyocera
KD210GH-2PU
Heron Island
Polycrystalline
210W
14.14%