Heterojunction and Passivated Contacts: A Simple Method to Extract Both n/tco and p/tco Contacts Resistivity

Abstract

High fill factor value is still a hot topic in Heterojunction (HJT) solar cells. Despite major improvement regarding the metallization losses using a novel encapsulation scheme like the SmartWire approach [1], the other series resistance contributions are still difficult to evaluate. Contacts between amorphous doped layers and transparent conducting oxides remain the main electrical barriers for both electrons and holes carriers. This work focuses on the series resistance breakdown of a high efficiency 6 inches HJT cell (eta=22.4%, FF=80.3%, Voc=738 mV, Jsc=37.8 mA/cm2) by comparing first two different existing methods to extract the series resistance, the European Standard EN60891 and the SunVoc. We present then two TLM (Transfer Length Method) dedicated structures to extract both the a-Si:H(n)/TCO and a-Si:H(p)/TCO contact resistivity. This enables us to rank each contribution of the series resistance from interfaces, TCO sheet resistance and the final metallization.