There are numerous existing cell designs, which integrate the advanced laboratory features used in advanced technologies. Several approaches have been used in niche markets like solar cars and space technologies like PERC, PERL, PERT cells.
High efficiency solar cells
Recently, several technologies were developed for producing higher efficiency solar cells. Those technologies use different concepts and cell structures like bifacial solar cells. The bifacial cell can absorb light and generate electricity on both front and rear surfaces. It can achieve up to 30 % higher yield than conventional cells if properly installed on open outdoor areas or flat roofs.
The benefits of bifacial cells are looking similar from both sides with the front side being collecting emitter / and back side being back-surface-field (BSF). Also, it can be interconnected with standard stringer technologies like 5BB or multiwire. Rear light collection can increase energy yield by up to 30 %.
Bifacial cells can be either adapted for monocrystalline material (PERC) or for multicrystalline material (PERT).
Below we will understand more about each type of PERCPERLPERT cells.
Another way for increasing cell efficiency is achieved by reducing the surface recombination at the rear of the cell. The passivated emitter and rear contact (PERC) cell can decrease rear recombination by inserting a patterned dielectric layer between silicon and aluminum layers, so that only the aluminum comes in contact with a small portion of the cell area. The extra SiO2 or Al2O3 dielectric layers reduce electron surface recombination extensively, which leads to increased cell efficiency.
PERL cells stand for the passivated emitter with rear locally diffused cells, which uses micro electronic techniques to produce cells with high efficiencies approaching 25% under the standard AM 1.5 spectrum. The high quality oxide at the front surface- that significantly lowers the number of carriers which recombine at the surface- is the passivated emitter. The rear emitter is locally diffused only at the metal contacts to minimize the recombination at the rear while maintaining good electrical contact.
PERT are not similar to standard cells or PERC. Both use an aluminum alloy BSF, while PERT - which stands for Passivated Emitter Rear Totally Diffused- cells have a diffused rear surface. In p-PERT, the emitter of p-type based wafer is formed with phoshphorus diffusion and BSF is realized with boron doping. PERT cells do not show the same significant light induced degradation and can be adapted to bifacial.