Improving solar cell design is a major factor in improving energy consumption. Scientists have recently focused on making solar cells more efficient, flexible, and portable so that they can be integrated into everyday applications. As a result, novel light and flexible thin film solar cells have been developed. However, it is not easy to combine efficiency with flexibility. For a material (usually a semiconductor) to be efficient, it must have a small “band gap” – the energy required to excite charge carriers to conduct electricity – and absorb a large amount of sunlight and convert it into electricity. To date, no such efficient absorber has been developed that is suitable for thin-film solar cells.
Typically, charge carriers in a semiconductor are generated in pairs of negatively charged electrons and positively charged “holes” (essentially the “absence” of electrons). These electrons and holes must be separated for efficient electrical conduction. A class of materials called “ferroelectrics” can greatly facilitate this separation because of their spontaneous “electrical polarization,” a phenomenon analogous to spontaneous magnetization in iron. However, limited photovoltaic applications have been used due to large band gaps and poor conversion of light to electricity.
In a new study published in Applied Materials and Interfaces, scientists from Korea have addressed this problem and proposed a novel solution in the form of “antiperovskite” oxides called Ba4Pn2O, with Pn replacing arsenic (As) or antimony (Sb)). Using density functional theory calculations, scientists examined various physical properties of the antiperovskite oxides and found that they have spontaneous electrical polarization, making them ferroelectric in nature. Prof. Youngho Kang of Incheon National University, who led the study, explains: In the minimum energy configuration of the Ba4Pn2O structure, we found that the O ions and the Ba ions are shifted in opposite directions from their original positions. These shifts resulted in a non-zero electrical polarization, a classic signature of ferroelectricity. “
Since spontaneous polarization aids in the separation of electron-hole pairs, this implied that antiperovskite oxides could efficiently extract charge carriers. In addition, the calculations showed that their band gaps are ideal for efficient sunlight absorption, so that even a very thin layer of Ba4Pn2O delivers a significant photocurrent.
Such promising results excited the scientists about the future prospects of thin-film solar cells. Prof. Kang suspects: “Our results are a firm confirmation that antiperovskites can be efficient absorbers for thin film solar cells. Due to their versatility, there can be several real applications for these solar cells, even for charging cell phones in sunlight. In addition, their flexibility can allow it to make self-propelled wearable devices such as smartwatches. “
Source of the story:
Materials provided by Incheon National University. Note: The content can be edited by style and length.