Deep level transient spectroscopy measurements of silicon heterojunction cells

Excellent open circuit voltage $(V_{oc})$ reported by Si Heterojunction (Si-HJ) solar cells has been a topic of considerable interest among the PV community. One of the reasons attributed to this large $V_{oc}$ is the reduction of interface recombination due to the presence of an inversion layer at a-Si:H/cSi interface. Here, we employ deep level transient spectroscopy (DLTS) measurements of silicon heterojunction cells (Si-HJ) to probe process induced interface traps at the a-Si:H/cSi interface. Interestingly, contrary to literature reports, we find both majority and minority peaks in differently processed Si-HJ solar cells - a result which could have interesting implications towards performance optimization.