Incorporation of Liquid Metal Gallium into Carbon Electrode for Efficient Charge Transportation in Planar Perovskite Solar Cells

Abstract

Carbon electrode-based perovskite solar cells (C-PSCs) exhibit a promising future for commercialization, due to their low cost, facile fabrication, and mass production potential. However, compared with metal-based counter electrodes, carbon electrodes (CEs) often suffer from relatively low electrical conductivity, porous and rough morphology leading to poor interfacial contact with the underneath layer thereby restricting the power conversion efficiency (PCE) of C-PSCs. Herein, a simple approach is presented to prepare liquid metal/carbon composite electrodes by uniformly dispersing liquid gallium droplets into CEs to enhance both the electrical conductivity and interfacial contact between carbon and the adjacent layer. Compared to control devices without Ga, the Ga-embedded carbon also creates a more favorable energy band alignment with the hole transport layer underneath for efficient hole transport, thus suppressing recombination at the interfaces. By optimizing the weight ratio between Ga and the carbon paste, the corresponding C-PSCs deliver an optimum PCE of 13.99% with a higher fill factor (68.95%) compared to pristine C-PSCs (PCE = 13.13%). In addition, the Ga-containing devices demonstrate reinforced thermal stability with 65% efficiency retention after 1800 min under a thermal stress of 80 °C without encapsulation.