This project managed by The University of New South Wales aimed at developing new solar cell technology that would lower the costs for making such solar cells while simultaneously raising their efficiencies with the hope that industry would engage in the commercialisation and large-scale manufacturing of the technology.
Report extract
The focus of the ARENA 1-060 project has been the development and commercialisation of new technology capable of achieving high efficiency silicon solar cells at low cost. Often, achieving higher efficiencies requires greater levels of sophistication with corresponding increased costs. In comparison, the priority for the technologies being developed in this project has been for the use of increased simplicity and the ability to use lower cost materials such as copper instead of silver for the metal contacts and low quality, low cost silicon wafers instead of those produced using the highest purity of silicon and with minimal crystallograghic defects.
The success in achieving the latter has been a particularly important outcome for this project given the dominance that the silicon wafers have in determining the cost of typical silicon solar cells.
The high efficiency solar cell design used in this work is shown in Figure 1 below and is known as the Passivated Emitter and Rear Cell (PERC). This was developed at UNSW during the 1980’s and has been responsible for many performance world records, both at UNSW and also by industry partners in collaboration with UNSW. Of particular importance in the commercial implementation of this cell design has been the development and implementation of three important technologies that have each led to significantly reduced costs while simultaneously enhancing the performance of the devices. The first of these has been the elimination of all microelectronics grade processing such as the use of photolithography to pattern dielectric layers, being replaced by a simple laser process which simultaneously patterns the dielectric while simultaneously melting the underlying silicon to facilitate the formation of a heavily doped (n++) region directly under the metal where it has significant performance benefits. The second of these has been the replacement of the expensive silver metal contacts with low cost plated copper contacts, which can be formed particularly simply since the copper plating naturally aligns automatically to where the laser melted the silicon and formed the n++ heavily doped silicon regions. The third and most important of these, has been the development of a new hydrogen passivation technology that is being widely regarded as a breakthrough for silicon photovoltaics. This is because the costs for making silicon solar cells are strongly dominated by the costs for the silicon wafer and yet this new passivation technology is able to transform low cost, low quality silicon wafers into ones that are comparable in quality to the highest quality wafers that would typically cost >100 times more.
