One-Step Formation of Low Work-Function, Transparent and Conductive MgFx Oy Electron Extraction for Silicon Solar Cells.

Abstract

The development of high‐performance dopant‐free silicon solar cells is severely bottlenecked by opaque electron selective contact. In this paper, high transmittance (80.5% on glass) and low work function (2.92 eV) lithium fluoride (LiF x )/MgF x O y electron contact stack by tailoring the composition of MgF x O y hybrid film is reported. This hybrid structure exhibits a high conductivity (2978.4 S cm−1) and a low contact resistivity (2.0 mΩ cm2). The element profile of LiF x /MgF x O y contact is measured and the reaction kinetics is analyzed. As a proof‐of‐concept, this electron selective contact is applied for dopant‐free silicon solar cells. An impressive efficiency of 21.3% is achieved on dopant‐free monofacial solar cell with molybdenum oxide (MoO x )/zinc‐doped indium oxide (IZO) hole contact. An efficiency bifaciality of 71% is obtained for dopant‐free bifacial solar cell with full‐area LiF x /MgF x O y /ITO (tin‐doped indium oxide) transparent electron contact. It is the highest efficiency bifaciality so far for dopant‐free bifacial solar cells to the best knowledge. Both cell configurations with LiF x /MgF x O y contacts show excellent environment stability. The cell efficiency maintains more than 95% of its initial value after keeping in air for 1500 h. This work provides a new idea to achieve transparent electron contact, showing a great potential for high‐efficiency and low‐cost optoelectronic devices.