Current Status of High-efficiency a-Si/c-Si Heterojunction Solar Cells: A Review

Heterojunction with intrinsic thin film (HIT) is a stable and efficient device because it blends the strength of crystalline silicon and amorphous silicon. The cells can be produced at low temperatures, usually below 200°C, which decreases the thermal budget and allows the use of thinner wafers, resulting in a decrease in production cost. Heterojunction silicon solar cells use silicon substrates for both absorption and transport, and a microcrystalline or amorphous thin layer of silicon for the purpose of junction and passivation formation. The top electrode is composed of a metal grid and transparent conductive oxide (TCO). Heterojunction solar cells have attracted considerable attention because they achieve efficiencies up to 26.3, which is close to the theoretical efficiency. The low-temperature process allows the handling of silicon substrates less than 100 μm in thickness with a high yield. The main characteristic is the use of metal contacts in this technology, which are extremely recombination active in conventional diffused junctions, and can be distinguished from the absorber through the introduction of a layer with a wide band gap. A high open circuit voltage is generally achieved with heterojunction devices without the need for valuable patterning technology.