A polarization-driven guide to making high-performance, versatile solar cells

Improving solar cell design is integral for improving energy consumption. Scientists have lately focused on making solar cells more efficient, flexible, and portable to enable their integration into everyday applications. Consequently, novel lightweight and flexible thin film solar cells have been developed. It is, however, 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 for electrical conduction--and should absorb and convert a large portion of the sunlight into electricity. Till date, no such efficient absorber suitable for thin film solar cells has been developed.

Typically, charge carriers in a semiconductor are generated in pairs of negatively charged electrons and positively charged "holes" (essentially, the "absence" of electrons). For efficient electrical conduction, these electrons and holes need to be separated. A class of materials called "ferroelectrics" can greatly facilitate this separation, thanks to their spontaneous "electric polarization," a phenomenon analogous to spontaneous magnetization in iron. However, due to large band gaps and poor light-to-electricity conversion, they have seen limited photovoltaic applications.

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