Title: Perovskite Solar Cells; Outshining Silicon
Abstract:
The cost of generating electricity from sun light using photovoltaic devices has continued to drop extensively over the last decade. Now in some locations in the world, PV generated electricity is cheaper than that from any other source. As the costs continue to drop and the efficiency of the PV modules continues to rise, the economic argument for globally widespread deployment of PV will become impossible to ignore. There have already been such advances in manufacturing the PV modules, that now the majority of the cost of a PV installation is the non-module costs, such as physical frames, electrical power handling, land and other soft costs. Therefore, from a PV technology perspective the most straight forward means to ensure the continuing drop in the cost of PV electricity is to enhance the efficiency of the modules. Current deployed PV is predominantly based on single-junction crystalline silicon. Most modules today are around 15 to 17% efficiency, with the more advanced “silicon technologies” promising modules of around 22%, but single junction silicon has a practical efficiency limit of around 25%. To move beyond this will require fundamentally superior technologies.
Within the last few years organic-inorganic halide perovskites have risen to become a very promising PV material, captivating the research community, with the lab based cell efficiency rising form 4% to over 20% within a few years. In the most efficient devices, the perovskite semiconductor is present as a solid absorber layer sandwiched between negative (n) and positive (p)-type charge collection contacts. The perovskite itself is crystalized at low temperature by either, mixing precursor salts in a solvent and casting from solution, or via sublimation of the same salts under vacuum. Improving solar cell operation is reliant upon understanding and controlling thin-film crystallisation and controlling the nature of the p and n-type contacts. In addition, understanding and enhancing long term stability of the materials and devices if a key driver. One key advantage perovskites have over silicon is that the band gap (the lowest energy at which the material absorbs light) can be tuned broadly from around 1.2eV to 2.4eV. This enables the possibility of realising multi-junction solar cells, which could deliver much higher efficiency than single junction silicon, by either combining perovskites with silicon, or on their own.
Here I will present our work on developing thin film perovskite solar cells, introducing the technology and putting it into the broader perspective of the global PV industry. I will discuss areas in which we have made recent advances and discuss the current status and potential for the “hybrid” perovskite-on-silicon tandem concept. I will also present broader applications where perovskite cells could find markets not currently met with crystalline silicon PV.
Bio:
Professor Henry J. Snaith FRS leads a research group at Oxford University and is CSO and Founder of Oxford PV Ltd. His work is focused on developing new materials for photovoltaics and understanding and controlling the physical processes occurring within the devices. He has made a number of advances and discoveries, with the most notable being the discovery of the remarkable PV properties of metal halide perovskites. He was awarded the Institute of Physics Patterson Medal in 2012, named as one of "natures ten" people who mattered in 2013, received the Materials Research Society Outstanding Young Investigator award in 2014 and elected as a member of the Royal Society in 2015. In December 2010 he founded Oxford PV Ltd. which is commercialising the perovskite solar technology transferred from his University Laboratory, which in on track to deliver the highest efficiency lowest cost next generation PV technology.
