Solar cells absorb energy from sunlight, and transform that energy into electricity. Solar cells, also referred to as photovoltaic cells (PV) or photoelectric cells, consist of different materials depending upon intended use and desired cost, but keep the same structure.

The top layer of a solar cell consists of glass with an anti-reflective coating. The glass protects the materials beneath it, and the coat helps sunlight reach the semiconductors. Thin metallic strips under the glass form the “grid” pattern, which complete the top layer.

The middle layer of a solar cell is most important. This is made from two (2) layers of semiconductors, which absorb solar energy through photovoltaic effect. The first layer is made of n-type material (negatively charged): typically silicon mixed with small amounts of phosphorous. The second layer is p-type material (positively charged) created through a mixture of silicon and small amounts of boron.

The bottom layer of a solar cell is similar to the top layer. There’s a metallic electrode directly under the p-type semiconductor, which works with the metallic strips in the top layer to create electric current. This is covered with a reflective layer to reduce loss of sunlight.

Each solar cell has the capacity to produce a specific amount of electricity. To increase electric output many solar cells are connected to form a solar panel. Solar panels are handled as one piece, but each cell works independently; the panel collects electricity from each cell combining the total electrical output. Common terms for solar panels include: • photovoltaic modules • photovoltaic panels • PV modules • PV panels • solar modules Solar panels are most commonly made from sixty (60) cells. These are connected in series with three (3) bypass diodes installed on each sub-string of twenty (20) cells. These help cells continue supplying power at reduced rates when a problem occurs. The solar cells on the panel absorb sunlight, and generate DC (Direct Current) electricity. The DC voltage is generally capped at 600 volts in the US, and 1000 volts in the EU. This electricity must be converted into AC (Alternating Current) through an inverter to be usable for most purposes. Both solar panels and inverters include nameplates. These are labels indicating the amount of power they produce under industry-standard test conditions. They represent the power output under ideal conditions, which few experience for more than a few moments at a time in real use.

There are several different types of solar cells. The majority of today’s solar panels are comprised of cells made from either monocrystalline or polycrystalline silicon. Today’s differences between monocrystalline and polycrystalline cells are negligible. The primary consideration in selecting solar cells and panels is the quality of the manufacturer.

Solar cells made from monocrystalline silicon are easily recognized by their uniform dark color, and rounded edges. These cells are made from a single crystal of silicon, have higher efficiency rates (15% to 20%), and perform well in low-light or lab conditions. They have higher outputs, occupy less space, and last longest; making them most expensive. Solar panels made with monocrystalline cells tend to be more durable than others in high temperatures, but their output is significantly reduced by shade, dirt, and dust. This is why they’re often paired with a microinverter, which converts DC electricity to AC for each individual panel. Common terms for monocrystalline silicon cells and panels include: • Mono-Si • Mono c-Si • Si • Single-Crystal Silicon

Solar cells made from polycrystalline silicon are easily recognized by their square shape, and textured appearance—resembling granite countertop. These cells are made from multiple silicon crystals, which wastes less material and makes manufacturing more efficient. This makes them more cost-effective than monocrystalline, but with slightly less efficiency (13% to 16%) based on lower purity. Solar panels made with polycrystalline cells have comparable output to monocrystalline modules, but require more space, have a shorter lifespan, and are affected by hot temperatures to a greater degree. Common terms for polycrystalline silicon cells and panels include: • Multi-Si • Multicrystalline Silicon • P-Si • Poly-Si • Polysilicon