Long-range energy transfer in singlet fission materials
Despite their early promise and intrinsic sustainability (low embodied energy, efficient use of abundant and non-toxic materials), organic photovoltaics still struggle with efficiency, stability and cost. One of the problems is the lack of long-range (>>10nm) energy transfer, which imposes severe limitations on the device geometry and precludes the use of planar bi-layer geometry solar cells.
To solve this problem you will use 'singlet fission' materials in a new way. Singlet fission is a process whereby a photo-excited singlet (spin-0) exciton is split into two triplet (spin-1) excitons. Recent work shows that the complex interplay between the singlet and triplet excitons increases the energy transfer distance by over an order of magnitude on sub-ns timescales. Therefore, in this project you will study the mixing of singlet and triplet excitons to understand the detailed physics of energy transfer in singlet fission materials. The overall aim is to produce high efficiency bi-layer solar cells.
To do this, you will use ultrafast lasers to make real-time 'movies' of energy dynamics following light absorption in Sheffield’s new ultrafast laser facility. You will also make and characterise thin films and bilayer solar cells in Sheffield’s refurbished cleanrooms and at the new X-ray facility.