High‐Performance Organic‐Silicon Heterojunction Solar Cells by Using Al‐Doped ZnO as Cathode Interlayer

Organic‐silicon heterojunction solar cells have recently emerged as a promising photovoltaic technique with the attractiveness of good performance and ease of processing. However, the poor collection property of electrons in cathodic interface is one of the most critical problems to be solved. In this study, a novel application of solution‐processed inorganic semiconductor nanocrystals of aluminum‐doped zinc oxide (AZO) is presented as cathode interlayer between the n‐type silicon (n‐Si) and rear aluminum (Al) electrode. With appropriate annealing temperature and doping concentration, the contact of n‐Si/AZO/Al exhibits a resistivity as low as 3 mΩ cm⁻². It is found that annealing the spin‐coated AZO solution at 200 °C is benefit to both formation of uniform film and sufficient replacement Zn atoms with Al atoms. Chemical structure investigations reveal the existence of AlOSi bonds at the interface, which may help to reduce the dangling bonds of n‐Si and deliver improved passivation. These AZO thin films are successfully used in planar n‐Si/PEDOT:PSS heterojunction solar cells as efficient electron‐selective layers, rendering a 10% relative increase in efficiency over the reference cells (13.6 over 12.3%). Our finding fully demonstrates its promising potential of this low‐temperature solution‐processed AZO interlayer for applications not only in hybrid solar cells but also in other types of silicon‐based photovoltaic devices.