Understanding and design of efficient carrier-selective contacts for solar cells

Numerous efforts have been devoted to either understanding or fabricating efficient carrier-selective contacts, since they play a significantly crucial role in high-performance solar cells. In this work, we demonstrate that the asymmetry between electron conductivity and hole conductivity is important but far not enough for efficient carrier-selective contacts. Taking electron-selective contacts as examples, cell performances are greatly affected by the electron conductivity, the hole conductivity, and the work function of electron-selective materials, together with conduction and valance band offset between absorbers and electron-selective layers. When designing efficient electron-selective contacts, all these factors should be considered to mitigate carrier recombination and downward bending of the electron quasi-Fermi level within and around the contacts and to ensure low interfacial resistance for electrons. Although the absorber is crystalline silicon in the study, we believe that our understanding and design guidelines are also applicable to solar cells based on other absorbers.