Molecular Recombination Junction for Vacuum-Deposited Perovskite/Silicon Two-Terminal Tandem Solar Cells

Abstract

The use of commercial, Czochralski-grown silicon wafers as bottom cells in two-terminal perovskite/silicon tandem configurations often leads to defects in the top perovskite absorber due to their rough surfaces, featuring μm-sized pyramids and saw damages. Most recombination junctions in two-terminal tandem cells employ high conductive indium tin oxide which increases the effect of local shunts in the top cell by connecting them. We use Suns–V_OC with selective illumination and external quantum efficiency measurements to identify these shunts. Additionally, we show that a molecular recombination junction composed of an n-doped C₆₀ layer and a p-doped conjugated arylamine layer alleviates the effect of the shunts in the top cell, which we attribute to the lower lateral conductivity of the organic layers. This enables us to prepare two-terminal tandem devices using fully evaporated top cells on Czochralski textured silicon heterojunction cells with V_OCs of up to 1.84 V and efficiencies above 22%.