6.3 Carrier Selective Contacts for Boosting Silicon Solar Cell Efficiency
UNSW has been partnering with a consortium of top US and international universities on next-generation silicon solar cells with targeted efficiencies of 29%, as part of the US Department of Energy SunShot Initiative (Foundational Program to Advance Cell Efficiency II (FPACE II)). This US$3.5 million grant is led by Arizona State University (ASU) with UNSW listed as a collaborator, along with MIT, Caltech and the Swiss Federal Institute of Technology.
UNSW’s involvement is being coordinated through the Australia-US Institute for Advanced Photovoltaics (AUSIAPV). The aim of the program is to develop a novel device structure for ultrathin crystalline silicon (c-Si) solar cells based on “carrier selective contacts”, with targeted efficiencies of 29%. UNSW contributes device modelling (e.g. using Sentaurus TCAD), materials deposition (e.g. via atomic layer deposition), characterisation and integration of selected wide bandgap materials (e.g. GaP) as carrier selective contacts for the novel silicon cell structure as part of a collaborative effort.
The motivation of using carrier selective contacts (CSCs) via deposited semiconductor layers that can induce strong inversion in the underlying silicon (Figure 6.3.1b), while allowing efficient carrier transport, is to avoid non-idealities associated with diffused junctions. The very low surface recombination velocities that can be achieved using these hetero-structures allow much higher open circuit voltages, especially on ultrathin silicon with appropriate light-trapping schemes.