HJT Solar Panel

Heterojunction solar panels work similarly to other PV modules, under the photovoltaic effect, with the main difference that this technology uses three layers of absorbing materials combining thin-film and traditional photovoltaic technologies. The process involves connecting the load to the terminals of the module, with the photons being converted into electricity and generating an electric current, flowing through the load
To generate electricity, a photon impacts the P-N junction absorber and excites an electron, causing it to move to the conduction band and creating an electron-hole (e-h) pair.
The excited electron is collected by the terminal connected to the P-doped layer, creating the electricity that flows through the load.
After flowing through the load, the electron flows back to the rear contact of the cell and recombines with a hole, ending that particular e-h pair. This is constantly happening as the modules generate electricity.
A phenomenon called surface recombination occurs in standard c-Si PV modules, which limits their efficiency. During this process, an excited electron pairs with a hole at the surface of the material, causing them to recombine without the electron being collected and flowing as an electric current.
To reduce surface recombination, HJT cells separate the highly recombinative-active (ohmic) contacts from the wafer-based layer using a passivating semiconductor film with a wider bandgap layer made out of a-Si:H. This buffer layer makes the charge trickle slow enough to create a high voltage, but fast enough to avoid recombination before electrons are collected, increasing the efficiency for the HJT cell.
During the light-absorbing process, all of the three semiconductor layers will be absorbing photons and converting them into electricity.
The first photons arriving will be absorbed by the exterior a-Si:H layer, converting them into electricity. The majority of the photons, however, are converted by the c-Si layer, which has the highest solar conversion efficiency among the materials in the cell. The remaining photons are finally converted by the a-Si:H layer at the rear side of the module. This three-step process is the reason why monofacial HJT solar cells have achieved solar efficiencies of up to 26.7%.

An individual solar cell is made up of extremely thin materials that are arranged so they can capture as much sunlight energy as possible that hit their surfaces. Of course, not all of the light that hits the cell's surface is absorbed. Some is reflected or actually passes right through the cell.
Heterojunction solar cell use a three-layer process to catch as much sunlight energy as possible. The silicon wafer in the middle of the “sandwich”, does the most of the sunlight to electricity conversion.
The top layer of Amorphous silicon that catches some sunlight before it meets the crystalline layer, is the first tier or “net”. The second as we mentioned earlier, is the middle wafer and then there is the bottom or third-tier of Amorphous silicon that further enhances the cell's ability to grab many photons that would otherwise pass through the cell completely or bounce right out of it. This is a simple, yet unique method to increase efficiency without adding much cost.
So, by creating a solar panel from three layers of different silicon, means the resulting HJT equipped panel can reach high efficiencies of over 21%, when compared to other panels using a conventional technical approach.