What are the different types of photovoltaic modules?
Photovoltaic systems bring convenience and environmental benefits to people. So, what are the different types of photovoltaic modules?
1. Crystalline Silicon Photovoltaic Modules
Crystalline silicon photovoltaic modules generally consist of a top cover glass, encapsulant material, back cover, solar cells, interconnects, busbars, and a frame (except for frameless modules). These modules use crystalline silicon as the base material, with P-type and N-type layers, and positive and negative output electrodes.
The difference between monocrystalline silicon and polycrystalline silicon mainly lies in the processing methods, which result in different atomic structures and, consequently, different physical properties and conversion efficiencies. With advancements in silicon materials and wafer cutting technologies, the cost of monocrystalline silicon wafers has continued to decrease, and its market share has steadily increased. The P-type and N-type crystalline silicon photovoltaic modules use different technological approaches, with the main distinction being in the manufacturing process.
Heterojunction (HJT) Photovoltaic Modules
In HJT cells, both monocrystalline silicon and amorphous silicon are present, utilizing the heterojunction structure of an amorphous silicon thin film on a monocrystalline silicon substrate. This structure effectively solves the high carrier recombination loss at the doped layer and substrate contact area found in conventional photovoltaic modules. HJT modules combine the advantages of both monocrystalline silicon and amorphous silicon, offering high stability, high conversion efficiency, low degradation, fewer process steps, and lower cost.
Tunnel Oxide Passivated Contact (TOPCon) Photovoltaic Modules
TOPCon modules feature a composite structure with doped polycrystalline silicon and an ultra-thin silicon oxide layer on the back. This structure forms an excellent passivated contact, which not only passivates the back surface of the photovoltaic module but also reduces interface recombination, enhancing overall module performance.
Interdigitated Back Contact (IBC) Photovoltaic Modules
In IBC modules, the PN junction and metal contact electrodes are arranged in an interdigitated pattern on the back of the module. This avoids the shading of incident light by the front metal grid and creates a light-trapping structure on the front surface with an anti-reflective layer and inverted pyramid textured surface, maximizing light absorption. Derived from the conventional aluminum back surface field (BSF) structure, this design uses an aluminum oxide film to passivate the back surface, increasing the potential difference of the PN junction, reducing carrier recombination, and improving open-circuit voltage. Additionally, the passivation layer acts as a back reflector, enhancing the absorption of long-wavelength light and increasing short-circuit current, which improves the module’s efficiency.
2. Thin-Film Photovoltaic Modules
Cadmium Telluride (CdTe) Photovoltaic Modules
CdTe photovoltaic modules typically consist of a P-CdTe and N-CdS PN junction and can be divided into an upper substrate and a lower substrate structure. The upper substrate usually uses a transparent material (such as glass), while the lower substrate typically uses an opaque flexible material (such as stainless steel).
Copper Indium Gallium Selenide (CIGS) Photovoltaic Modules
Copper Indium Gallium Selenide (CIGS) thin-film material is a ternary compound semiconductor with a high optical absorption coefficient, which gives it the highest optical absorption coefficient among all photovoltaic modules, leading to high conversion efficiency. Additionally, as CIGS is a direct bandgap semiconductor, it performs well under low light conditions, meaning it generates more power in cloudy or rainy weather than other types of photovoltaic modules.
3. Third-Generation Photovoltaic Modules
Perovskite Photovoltaic Modules
Perovskite modules are based on a stable molecular structure with unique electromagnetic properties and excellent light absorption and electrocatalytic capabilities, making them suitable for use in photovoltaic modules.
Organic Photovoltaic Modules
Organic photovoltaic modules are a rapidly emerging type of photovoltaic technology that uses organic materials with light-sensitive properties as semiconductor materials. These organic materials have conjugated structures and conductive properties. Organic modules offer high conversion efficiency, excellent performance, and long lifespan, along with many advantages not found in inorganic photovoltaic modules, such as structural diversity, color variety, and flexibility. They have significant potential for applications in building-integrated photovoltaics (BIPV), wearable photovoltaic devices, and other innovative fields.