**2. Cost structure of PV system**

To begin the discussion of the cost of solar panels, we split the cost of thin film PV system into four major parts:


Film deposition materials

Equipment depreciation

labor Freight

Throughput Efficiency automation Volume

Fig. 3. Relationship between fabrication process, cost structure, and production of thin film

back TCO and the reflector form the back contact (Fig. 4). The Si p-i-n junction absorbs sun light and generates photocarriers, which are collected by the conductive, front and back contacts. The substrate (e.g., glass) provides mechanical support for all the layers. Stacking two a-Si/µc-Si cells on top of each other forms the tandem junction structure, which is also

Depends on the type of substrates on which the films are grown, there are basically two kinds of cell structures. 1) "Substrate" structure, where none-transparent substrates, i.e., metal foils, are used for growing the film stack. Sun light enters the cell from the top of the film stack by going through the top TCO. 2) "Superstrate" structure, where transparent substrates like glass or plastic films are used. Sun light enters the cell through the transparent glass/plastics and the TCO layer. The growth order of the Si p-i-n diodes are reversed in the two structures. The monolithically integrated superstrate type solar cells have superb encapsulation and compatibility with conventional electrical and safety

The Si p-i-n junction is where the sun light is absorbed and converted to charge carriers, i.e., electrons and holes. Differs from crystalline Si (c-Si), a-Si for PV and other applications (e.g., thin film transistor, TFT) are actually hydrogenated amorphous silicon alloy (a-Si:H, here noted as a-Si for simplicity), in which the H atoms passivate the otherwise high-density Si dangling bonds in pure amorphous Si film that introduce trap states and severely affect the film electrical properties. Normally the H content can be as high as a few percent. The a-Si completely loses the periodical atomic lattice structure; instead, the Si atoms randomly

Package/ assembly

Direct material cost

Film deposition process

Energy consumption

sandwiched between the front and back TCOs.

regulations, thus holding a dominant market share.

**3.1 PV active Si p-i-n layers** 

**Fabrication Process:**

**Cost structure:**

**Module production:**

PV modules.

Sharing similar cost percentage of the first three parts with crystalline Si PV systems, the much lower module cost gives thin film PV system lower overall cost and a higher development potential. An increase or decrease of the efficiency of the module implies an increment or a reduction of the BOS and installation costs, respectively. Nevertheless, the financing and inverter cost remain always the same. Therefore, the use of lower efficiency thin film modules are financially more favorable in those cases in which the value of the installed area is not relevant. Thin film panels are thus more applicable to the PV electricity power plants built in remote areas like deserts. Large volume production and deployment is the key factor to fully demonstrate the financial benefit of thin film solar modules.

The cost of thin film modules, in turn is composed of five major components (Jäger-Waldau 2007):


As seen from the relationship of the thin film PV module cost structure summarized in Fig. 3, the process technology determines the direct material and energy consumption, equipment depreciation and ultimately the panel efficiency, which in turn affect the panel cost. In another word, more advanced module process technology leads to both higher panel efficiency and lower panel cost. Thus in this chapter, we put our focus on the process details of the manufacturing of modern, large-area a-Si/µc-Si solar panels.
