There are numerous cell designs that integrate the major technological advances discovered and used in laboratories. These types of cells have been used in niche markets such as solar cars and space technologies, including PERC, PERL and PERT cells.

High efficiency solar cells

Recently, several technologies have been developed to produce higher efficiency solar cells. These technologies use different cell concepts and structures, such as bifacial solar cells. The bifacial cell can absorb light and generate electricity on both the front and rear surfaces. It can achieve up to 30% higher efficiency than conventional cells if properly installed on open outdoor areas or flat roofs. The advantages of bifacial cells are that they look similar from both sides, as the front side is the emitter collector and the rear side is the back surface (BSF). In addition, it can interface with standard stringer technologies such as 5BB or multiwire. Backside light harvesting can increase energy yield by up to 30%. Bifacial cells can be adapted to single-crystalline material (PERC) or multi-crystalline material (PERT).

PERC solar cells

Another way to increase cell efficiency is achieved by reducing surface recombination at the backside of the cell. The passivated emitter and back-contact (PERC) cell can decrease back recombination by inserting a patterned dielectric layer between the silicon and aluminum layers, so that only the aluminum contacts a small portion of the cell area. Additional dielectric layers of SiO2 or Al2O3 greatly reduce the surface recombination of electrons, leading to higher cell efficiency.  

PERL solar cells

PERL cells, short for passivated emitter and local back diffusion cells, use microelectronic techniques to produce cells with high efficiencies approaching 25% in the standard AM 1.5 spectrum. The high-quality oxide on the front surface, which significantly reduces the number of carriers recombining on the surface, is the passivated emitter. The back emitter is locally diffused only at the metal contacts to minimize backside recombination and maintain good electrical contact.  

PERT solar cells

PERTs are not similar to standard cells or PERCs.  Both use an aluminum alloy BSF, while PERT (Passivated Emitter Rear Totally Diffused) cells have a diffused back surface. In p-PERTs, the emitter of the p-type wafer is formed with phosphor diffusion and the BSF is made with boron doping. PERT cells do not show the same significant light-induced degradation and can be matched to bifacials.