Created on 08.19

What Are Solar Panels Made Of? A Layer-by-Layer Guide

Ask a procurement manager what is inside a solar panel and the first answer will probably be “cells and glass.” That is only part of it. A finished module also contains two encapsulant films, metal conductors, a protective rear layer, seals and electrical hardware. Change one of those items and the quotation may still show the same wattage, even though the module now weighs more, handles moisture differently or needs another mounting approach.

That is why the question matters in an RFQ. An importer may be checking container weight; an EPC buyer may be concerned about clamps and design loads; a coastal project has another set of concerns altogether. Knowing the basic module stack makes it easier to read a data sheet and to notice what the data sheet does not say.

What Are Solar Panels Made Of? The Short Answer

Take a conventional crystalline-silicon module and read it from the sunny side toward the roof or ground. Its laminate normally follows this order:

Front glass
Front encapsulant
Solar cells and metallic interconnects
Rear encapsulant
Polymer backsheet or rear glass

Around that laminate sit the edge seal and, on most current products, an aluminum frame. The junction box, leads and connectors are fitted at the rear. This is the usual arrangement, not a bill of materials for every product on the market. A double-glass bifacial module and a lightweight rooftop module can share the same sequence while using quite different thicknesses, films and frame designs. The quoted model’s documents remain the deciding reference.

A Layer-by-Layer Breakdown of a Solar Module

Front Glass

The outer surface is commonly made from low-iron tempered solar glass. Low iron content improves light transmission compared with ordinary window glass, while tempering increases resistance to impact and mechanical stress. Many modules also use textured or anti-reflective surfaces to reduce reflection and help more light reach the cells.

Glass thickness is not a universal indicator of quality. A glass-backsheet module may use a different front-glass thickness from a double-glass module, and larger-format modules introduce their own mechanical design considerations. For procurement, the more useful checks are the construction stated on the product data sheet, the module's certified mechanical-load ratings, its dimensions and weight, and the installation instructions for clamping and support.

Front and Rear Encapsulants

The cells do not sit loose between two sheets. A polymer film is placed on each side before the stack is laminated. EVA and POE are the names buyers see most often, but those labels cover many formulations; manufacturers may also combine materials in a co-extruded film.

Once laminated, the film keeps the cell circuit in place, provides optical contact with the glass and forms part of the moisture barrier. POE and co-extruded options often appear in designs where electrical resistivity or moisture behaviour is a particular concern. EVA, meanwhile, remains common and has a long production history. It would be a mistake to rank two modules from the word “POE” or “EVA” alone. Film formulation, lamination, edge protection and the rest of the package have to work together.

Solar Cells and Interconnects

In most mainstream modules, the active layer consists of crystalline-silicon cells. Monocrystalline silicon is widely used in current high-efficiency module designs, including P-type and N-type cell architectures. The cell converts sunlight into direct-current electricity; it should not be confused with the module as a whole, whose rated efficiency also reflects inactive areas, optical losses, and electrical losses.

Cells are connected by metallic ribbons or wires that collect and carry current through the circuit. Busbar and multi-wire designs vary among products. When reviewing a module, buyers should focus on the complete model specification and validated electrical characteristics rather than assuming that one visible cell pattern is automatically superior.

Close-up of a solar panel with visible photovoltaic cells and grid lines.

Backsheet or Rear Glass

At the back, the construction takes one of two familiar routes.

The first is a polymer backsheet, normally a multilayer film that provides insulation and closes the rear of the package. Its composition varies. "TPT" is sometimes used as a loose catch-all in sales material, so it should not be copied into a technical comparison unless the documentation for that model actually specifies it.

The other route is rear glass. It is widely used in bifacial modules, where the rear side must admit light as well as protect the cells. The extra glass can strengthen the environmental barrier, but it changes the practical side of the purchase too: pallet weight, manual handling, racking loads and freight calculations may all move.

Aluminum Frame and Edge Seal

Many solar modules use an anodized aluminum frame to protect laminate edges and provide mechanical mounting points. Frameless designs also exist, particularly among some double-glass products. Frame depth by itself does not establish snow- or wind-load capability; buyers should compare the certified mechanical-load rating and follow the manufacturer’s specified mounting zones and fastening method.

Edge seals and sealants help limit moisture entry at vulnerable interfaces. Their importance is easy to overlook because they occupy little visible area, but they are part of the overall barrier system formed by the glass, encapsulants, rear layer, and laminate process.

Junction Box, Bypass Diodes, Cables, and Connectors

The junction box is attached to the rear of the module and provides the electrical connection between the internal cell circuit and the external DC cables. It normally contains bypass diodes that allow current to pass around affected cell groups under partial shading or fault conditions, reducing the risk of severe local heating. This does not mean one bypass diode prevents a shaded cell from reducing the output of an entire string; system behavior depends on module circuitry, shading pattern, and array design.

For B2B procurement, confirm the junction-box protection rating, cable length, connector type, polarity, and compatibility with the project’s balance-of-system design. Connector mating should follow the equipment manufacturer’s instructions; visually similar connectors should not be assumed to be compatible.

Exploded view of a solar panel showing layers: front glass, encapsulants, solar cells, and rear glass.

How Module Materials Affect Durability

The materials spend their working life expanding and contracting in the sun, holding out humidity and carrying mechanical loads. A farm, a seafront warehouse and a desert array do not expose them to the same stresses. Nor can one premium-sounding ingredient guarantee a durable module. Design, lamination, production control, packaging, installation and operation all leave their mark.

What might an asset owner actually notice? The following faults are useful clues, although none identifies a root cause on its own:

Delamination appears as separation within the laminate. It can interfere with optics and with the package’s protection against the weather.
A yellowing or browning encapsulant deserves investigation because less light may be reaching the cells.
Cracks in a polymer backsheet raise insulation and moisture-ingress concerns.
Corrosion may show up on the frame, cell interconnects or other metal parts; location and construction influence where it starts.
Potential-induced degradation is not simply "bad glass" or "bad EVA." System voltage, grounding, humidity, temperature and several module materials can be involved.
Some cell microcracks begin before a pallet reaches site; others occur during handling, installation or operation. Many cannot be seen in an ordinary walk-through.

A name on a BOM will not diagnose any of these faults. Start with operating data and a visual inspection. Insulation tests, infrared thermography or electroluminescence imaging can then be selected if the symptoms and the project's O&M procedure justify them.

Glass-Backsheet vs. Double-Glass Modules

The two formats solve slightly different procurement problems, and neither wins by default.

A glass-backsheet module will often be lighter than a comparable double-glass model. That difference is welcome on rooftops and can matter when a container is close to its weight limit. The format also has a long field history. Even so, the backsheet construction, applicable fire information and climatic suitability still need to be checked for the offered model.

With double glass, the cell laminate is closed by glass on both faces. This gives many bifacial products a robust package, but the purchasing team has to account for the extra mass during lifting, packing and structural design. Rear glass also does not create a guaranteed bifacial gain. Ground reflectance, row height, tracking or racking, and rear-side shading decide how much of that potential becomes energy.

So the useful comparison is model against model, at the intended site. A blanket claim that either format always lasts longer is not enough for an approval decision.

B2B Procurement Checklist for Solar Module Materials

Before the purchase order is released, work through the questions below with the supplier. Some answers may have to come from the module manufacturer.

Is the model code consistent? The quotation, data sheet, certificate set, packing information and order confirmation should point to the same product and power class.
What is the physical build? Record glass-backsheet or double-glass, framed or frameless, and monofacial or bifacial. Do not infer one item from another.
Will the logistics plan still work? Module dimensions, unit weight, pallet count, container loading and handling limits belong in the commercial review, not in an afterthought before shipment.
Which load figure applies? Read front- and rear-side mechanical ratings together with the approved clamping zones. A load number without the specified mounting method is incomplete.
Does the site need additional testing evidence? A coastal project may call for salt-mist documentation; an agricultural site may raise ammonia exposure.IEC 61701covers salt-mist corrosion testing of a PV module, not a stand-alone certificate for its aluminum frame.
Are the electrical details usable on this project? Check the junction box, lead length, connector, maximum system voltage and fuse rating against the balance-of-system design.
What exactly does the warranty promise? Read the product warranty separately from the performance warranty, then note the manufacturer's first-year and annual degradation terms for this model.
Do the documents match the goods? A certificate for a related product family is useful only if the offered configuration remains within its stated scope.

What Information May Not Appear on a Data Sheet?

Data sheets are summaries. They normally cover electrical ratings, dimensions, weight, cell technology, basic construction, load ratings, temperature coefficients and system limits. They often stop short of naming every film grade or sub-supplier behind the glass, backsheet, frame, junction box and connectors.

Put any controlled-BOM requirement in the RFQ, along with requests for named component suppliers, extended environmental reports or lender documents. Asking after the order is placed may be too late. Disclosure depends on the manufacturer and product programme, and sometimes on confidentiality terms. Until the relevant document has been confirmed for the selected model, it should not be promised to a buyer.

How LANERGY Supports Solar Module Sourcing

LANERGY’s role is supply and export, not module manufacturing. For an overseas enquiry, the team can help narrow the available options, coordinate a quotation and collect the product documents available for the model being discussed. The manufacturing specification and warranty come from the relevant manufacturer. Stock status, price, lead time, certificate coverage and document availability must all be confirmed for the actual order.

When contacting LANERGY, include the destination market, power range, site conditions, preferred construction, required documents and estimated volume. A distributor may also want packaging and model-continuity information; an EPC buyer will usually need project and electrical constraints. The module catalog is a starting point. Final suitability still depends on the exact offer and its supporting documents.

FAQ: What Are Solar Panels Made Of?

Are all solar panels made from silicon?

No. Thin-film modules use other semiconductor materials and are built differently. The layer sequence in this article describes crystalline-silicon modules, the type most buyers will encounter in mainstream residential, C&I and utility quotations.

Is EVA or POE better for a solar module?

Not from the name alone. POE is attractive in designs that place particular weight on resistivity or moisture behaviour; EVA is established, widely processed and economical. The better choice is the film that has been qualified as part of the complete module design and is appropriate for the intended environment.

Does thicker glass or a deeper frame always mean a stronger module?

No. A 40 mm frame is not automatically a stronger purchasing choice than a 30 mm frame. Read the load ratings alongside module size, glass configuration, frame design, mounting instructions and clamp zones.

What should an importer request before placing an order?

Start with the current data sheet, certificate set, warranty and packing details, then check that every file relates to the quoted model. Put salt-mist, ammonia, fire, load or market-access requirements in the enquiry. If a document is essential to customs clearance, financing or technical approval, make it an order condition rather than an assumption.

Conclusion

Once buyers know what sits behind the glass, a module comparison becomes less superficial. Wattage and price still matter, but so do the two encapsulant films, cell circuit, rear closure, seals, frame and junction box. Read them as a package. Then check whether that package—and the paperwork supplied with it—fits the site, transport plan, mounting method and terms of purchase.