Materials and deposition methods for the manufacture of low-cost solar cells

Abstract

In order to drive rapid widespread global adoption of photovoltaics, solar panel cost must be further reduced. 40% of the cost of panels produced today comes directly just from the cost of the manufacturing methods used, and another 14% comes from active layer cost – so these are 2 areas to focus on when cutting costs. Thin films solar cells offer a route to reducing solar cells cost, both because they can be manufactured from solution without the use of expensive machines which require vacuum, and because their material costs can be lower. However, today these cost savings are cancelled out by the expensive long annealing steps under special atmospheres required to manufacture high quality thin film solar cells.

An annealing-free approach was developed for the fabrication of CZTS thin film active layers, through creation of a novel nanoparticle synthesis with a chemically-cleavable ligand. Charge transfer was successfully demonstrated, paving the way for an annealing-free solar cell based on this material and method.

A novel and highly-configurable spray-based system was developed for sequential deposition and treatment of nanoparticle films. With further optimisation, this system has the potential to precisely deposit nanoparticle monolayers without the need for vacuum which is required by other monolayer deposition technologies. This process can also scale directly from lab to manufacture, enabling a faster route to industrialisation of lab-scale optimised solar cells.

A novel SnS nanoparticle synthesis was developed, based on the PbS nanoparticle synthesis which has given 10.6% efficient annealing-free solar cells following a decade of optimisations. The SnS synthesis was shown to emulate the PbS synthesis well, meaning that some optimisations could be ported across directly, saving development time. This system is promising as a non-toxic analogue to annealing-free PbS solar cells.