Solar energy is hot. In times of increasing energy consumption, solar cells are considered one of the key technologies towards a sustainable energy supply. Especially now with more and more countries reaching grid parity, solar energy becomes a real alternative for conventional electricity production. Despite the rising enthusiasm, solar cell conversion efficiencies are still fairly low. The challenge remains to increase efficiency while keeping the production costs low. Recent work of María Recamán Payo, researcher at the silicon photovoltaics (PV) group in imec, tackles the issue by applying a process technology called ‘selective epitaxy’ on bifacial solar cells. By optimizing the doping profile on the emitter side, she has managed to reduce recombination, a major cause for efficiency loss. Moreover, because selective epitaxy is a simple, one-step process, device production costs are bound to be lower.
A question of efficiency
Although the sun is the most abundant source of energy on the planet, solar cells only convert a fraction of that enormous potential into electricity. In fact, most PV solar cells have a theoretical efficiency ceiling, limiting the amount of energy they can extract from the sun. But with current technologies, we are still far from hitting that ceiling. To put things into perspective: even though the upper-limit conversion efficiency for silicon devices is calculated to be around 30%, solar cells in commercial solar panels typically only reach an efficiency of around 18%. Most PV research is therefore focused on finding solutions to close this gap, while at the same time keeping production costs low. “The field of PV has already made tremendous progress, for example by improving junction profiles and passivation layers."