Ambipolar Passivated Back Surface Field Layer for Silicon Photovoltaics

Abstract

The suppression of surface recombination is of primary importance for realizing efficient silicon photovoltaics, which is usually achieved by introducing passivation or back-surface field (BSF) layers. In this study, it is demonstrated for the first time that self-assembled, ferroelectric, and organic thin-films can be used as passivating BSF layers for both n- and p-type Si solar cells by switching polarization. The n-Si/PEDOT:PSS heterojunction solar cell with the ambipolar passivated BSF exhibits an efficiency of 18.37%, which is a record-high efficiency for organic semiconductor/n-Si heterojunction solar cells. In addition, homojunction p-Si solar cells with the ambipolar passivated BSF yield superior performance compared to aluminium-BSF cells. Finite-difference time-domain simulations reveal that the electric field due to the ferroelectric layer extends deep into the backside of Si, causing band bending and, consequently, reducing surface recombination. Moreover, the solar cell with passivated BSF maintains > 95% of its initial performance even after 1000 h of the standard damp heat test. This work endows Si-based photovoltaics with the superior passivation and high-performance which were previously exclusive to inorganics.