Society's reliance on fossil fuels for energy is driving climate change, resulting in rising global temperatures and associated rising sea levels, damage to natural ecosystems, and increased risks of extreme natural disasters. The most abundant alternative source of energy comes from the sun; the light irradiated from the sun carries enough power to supply the world with its current energy needs many times over. While photovoltaic panels made of silicon are being rapidly adopted on both rooftops and in utility scale solar parks, there are applications where the rigidity, weight, and relatively low efficiency of existing silicon solar panels bar their use. In addition, factories that produce silicon solar cells are extremely expensive, limiting the ability to rapidly ramp up silicon solar cell production to meet the growing clean energy needs of the world economy.
This project develops alternative materials and devices based on them, to enable efficient, low cost, rapidly scalable, and lightweight solar panels. The project focuses on a relatively new class of photovoltaic semiconductors; metal halide perovskites. These benefit from an unusual array of properties: they exhibit optoelectronic properties rivaling those of carefully manufactured single crystal semiconductors even when made through rapid printing techniques from inexpensive precursors. The materials absorb light strongly, so only very thin layers (less than 1 micrometer) are necessary to absorb all of the incoming sunlight which in turn allows them to be used in very light and flexible solar cells. Finally, their bandgap can be tuned by simple tuning of the material's chemical composition. This allows for the development of solar cells consisting of multiple semiconductor layers with complimentary bandgaps, which can reach theoretically higher efficiencies than those made from just one active semiconductor layers. Effectively, this allows us to stack multiple solar cells on top of each other, which absorb complimentary parts of the solar spectrum in a way that raises the overall efficiency of the final solar cells. A challenge of metal halide perovskites is their susceptibility to degradation when exposed to humidity or oxygen.
This project aims to develop metal halide perovskite materials and methods of depositing them to make very efficient solar cells. Specifically, methods for tuning the bandgap are a subject of intense research, as are methods of deposition, which should allow the technology to be scaled and approach commercial readiness. This is accomplished by tuning the chemical composition, altering the bandgap by both directly influencing the energetics of the metal and halide orbitals and also indirectly by introducing structural distortions which change the metal-halide orbital overlap. Understanding of the structural properties can also be used to understand degradation mechanisms in these materials. The goal is to use newly developed materials with new bandgaps and deposition methods to make efficient tandem solar cells made of two perovskite absorber layers. specifically, focus is also on understanding mechanisms relating the chemical and structural composition of the materials to bandgap and stability.
