Double Perovskite Solar Cells

Solar cells based on hybrid halide perovskite materials are the fastest growing solar technology in history, with starting point efficiencies of 3% in 2009 and now surpassing 22%; already comparable to industry standards such as poly-Si. However, despite the rather large leaps in efficiency, one of the main concerns has yet to be decisively addressed: the toxicity of the structure. Alternative lead-free structures in the forms of Bi(III) based compounds and Ci(I) compounds have recently been introduced as promising materials, yet their optoelectronic properties are suboptimal and the resulting devices are inefficient. Here the student will target new "double" perovskite structures. This newly introduced family of materials is based on the substitution of the lead centre with two different elements, initally Bi3+ and Ag+ 1 which occupy alternating centres of the octahedra, thus leading to an ordered double perovskite structure with cubic symmetry. Initial results show that these structures exhibit strong photoluminescence with lifetimes in the order of tens of nanoseconds, implying that photoexcited species are long-lived and trap densities are low, making them suitable for incorporation into solar cells.