Researchers Find New Way To Boost Solar Cell Efficiency by 35%

Researchers Find New Way To Boost Solar Cell Efficiency by 35%

Scientists at the University of Oulu, Finland have hinted at new ways to boost the efficiencies of solar cells. The recent findings by the researchers were published in the Advanced Electronic Materials journal. Their latest study advances in understanding the photovoltaic effect in ferroelectric crystals. The research talks about improving the electric output of the bulk photovoltaic effect (BPVE) via manipulation of ferroelectric domains in oxide perovskite crystals.

The researchers said that working on the Bulk Photovoltaic Effect (BPVE) could lead to a breakthrough in enhancing solar cell efficiencies. BPVE (Bulk Photovoltaic Effect) refers to a physical phenomenon where few materials can generate an electrical current when exposed to light, without requiring a p-n junction or an external electric field.

“In ordinary solar cells, the mechanism of harvesting the solar energy and then converting it into green electricity is based on the formation of p-n junctions of semiconductors. While the p-n junction has been invented for more than a century, widely used in the silicon industry nowadays, the BPVE is a more recently discovered physical phenomenon from the 1960s-1970s. The BPVE does not rely on p-n junctions to work under solar energy. It forms its own ‘‘self-junction’’ and, theoretically, it may break the physical limit of the Shockley-Queisser limit that prevents single p-n junction-based solar cells from being more efficient”, clarifies associate professor Yang Bai from the Microelectronics research unit.

35% Improvement In Output 

The team of researchers comprised Vasilii Balanov, Jani Peräntie, Jaakko Palosaari, Suhas Yadav, and Yang Bai. The team has claimed to have advanced in the multifunctional energy harvesting field. Using BPVE in practice is challenging at the moment, as the output power of BPVE-based cells is still negligible compared to those of p-n junction-based photovoltaic cells. In this study, Bai’s team proves that by creating a stacked domain structure, a 35% improvement on the output power of BPVE-based cells can be achieved. A domain is a submicron-sized region containing spontaneous polarizations orienting in the same direction, which can be switched by applying an external electric field.

The improvement of electric output from Bai’s BPVE device is achieved by applying an AC poling electric field, under which the microstructure (domains) inside the crystals will be better aligned compared to the situation under the conventionally used DC field. After removing the electric field, the domains stay at that better aligned state. The better aligned domains help to reduce recombination of electric charge carriers, and thus the energy conversion efficiency increases. The results of the work pave a way towards developing more efficient BPVE cells that can help to unlock multifunctionality in future photonic, computing, sensing and energy harvesting devices.

Challenges galore 

“The first concrete applications will be in small-scale sensing and computing devices, where in addition to the electric signals, we can input light of different wavelengths as an extra degree of freedom for operation. For example, we have previously proven the use of BPVE in filterless colour sensor. Other examples include components for neuromorphic computing and multi-source energy harvesters for IoT (internet of things) devices”, says Yang Bai.

Despite the breakthrough now achieved, there is still a lot of research work ahead. Yang is aware of the challenges and the future goals are clear.

“While we are advancing in the working mechanism inside the materials, the challenge still lies in the band gap of the materials, where we ideally need a material that simultaneously has a narrow band gap (to maximise visible light absorption) and a large spontaneous polarization (to maximize the open-circuit voltage). We have limited options for such materials. Most available materials nowadays only possess either a narrow band gap or a large spontaneous polarization, not both. In the near future, we will attempt to expand the material options”, muses associate professor Yang Bai on behalf of his whole group.