Renewables recently represented almost two-thirds of new net electricity capacity additions, with solar photovoltaics (PV) additions growing faster than any other fuel. Installed PV capacity recently surpassed 300 GW and the PV market will reach a volume of about 90 GW in 2017, mainly driven by China with almost half of the new installations. Today, auction prices for PV power plants reached record-low values of even less than 2c$/kWh. For the next five years, solar PV will represent the largest annual capacity additions for renewables, driven by continuous cost reductions and power conversion efficiency (PCE) improvements. Such rapid growth of PV capacity requires an even stronger focus on using abundant and sustainable materials as well as scalable production processes for solar cells and modules.
Silicon solar cell technology dominates the PV market since years, with thin films technologies (cadmium telluride (CdTe), copper indium gallium selenide (CIGS), others) reaching a total market share of less than 10%. This domination is continuously fuelled by advances in manufacturing excellence and increasing PCE. One example is the recent introduction of the Passivated Emitter and Rear Cell (PERC) technology in mass production that improves the PCE of the standard Aluminum Back-Surface Field (Al BSF) solar cells by 0.5-1% absolute, reaching about 22% PCE in production. Following the general trend to higher PV panel power conversion efficiencies to reduce overall PV systems costs, there is also a stronger emphasis on advanced solar cell architectures such as silicon heterojunction (SHJ) and Interdigitated Back-Contact (IBC) cells, accompanied by improvements in module technology.
The next technology steps are already being prepared at laboratory level: for example, tandem solar cells with a higher band gap top cell and lower band gap bottom cell better utilize the solar spectrum and have the potential to overcome the PCE limit of silicon solar cells of ca. 29%. Novel materials such as perovskites that also have the potential to be sustainable may play a crucial role in realizing such high-efficiency, low-cost tandem solar cells in production, but could also be used as a single-junction thin film technology.
This paper will review recent PV technology advances and will give an outlook on future technologies both in laboratory and production, with a discussion of the environmental impact.