How does a heterojunction solar cell work?

Its temperature coefficient. The temperature coefficient of a solar cell or module indicates how much the output power decreases per each degree increase in temperature. The lower the temperature coefficient, the less the efficiency drop will be as the temperature rises. Thin-film cells have a smaller temperature coefficient than crystalline modules and therefore lose less power as the temperature rises.

As in other systems, Panasonic's HIT® solar cells combine the advantages of both technologies, containing both crystalline and thin-film technology. In heterojunction solar cells, an ultra-thin monocrystalline silicon wafer is encased in an ultra-thin amorphous (thin film) silicon layer. Panasonic is also one of the very few module manufacturers using n-type wafers. Conventional monocrystalline wafers are based on p-type, Panasonic uses n-type because of their higher purity.

Solar cells with heterojunctions are first of all impressive for achieving a very high voltage through excellent surface passivation. The monocrystalline wafers are chemically polished and continuously improved. As a result, considerably less electrons are lost than with monocrystalline cells with rougher surfaces.

Combining two types of silicons (monocrystalline and amorphous) in the heterojunction cells is also advantageous - for example, comparing it to a silicon-metal compound. The high open-circuit voltage of heterojunction cells also has a positive effect. A higher open-circuit voltage causes the inverter to be activated earlier. As a result, direct power is converted into alternating power earlier. This increases the solar power yield and improves the maximum power of the module (Pmax).