Diaminomaleonitrile Lewis Base Additive for Push-Pull Electron Extraction for Efficient and Stable Tin-Based Perovskite Solar Cells

Tin-based perovskite solar cells (Sn-PSCs) have been attracting researchers' attention as a promising material for fabrication of eco-friendly perovskite solar cells. However, the power conversion efficiency (PCE) and the stability of Sn-PSCs are still inferior compared to those of lead-based PSCs. This is due to some basic problems in Sn perovskite materials, such as the easier oxidation of Sn2+ to Sn4+ leading to faster recombination, which increases electron loss in SnPSCs. In this work, we focused on minimizing the electron loss during transportation from the FASnI(3) perovskite layer to the adjacent electron-transport layer (ETL) by introducing diaminomaleonitrile (DAMN) in the perovskite precursor. DAMN with two cyano groups in its skeleton can work as an electron withdrawing group to extract electrons effectively from the perovskite layer and transfer them to the adjacent ETL. Our finding highlights that the FASnI(3)-DAMN-based PSCs possess a 42% higher electron mobility compared to pristine FASnI(3) and the transient photocurrent decay lifetimes are accelerated by 2.3 times, revealing an enhancement in electron transportation after incorporation of DAMN. Apart from the successful electron transportation enhancement, the FASnI(3)-DAMN perovskite absorbers showed a reduced charge carrier recombination rate, thanks to the simultaneous reduction of lattice strain of the FASnI(3)-DAMN film. Consequently, the fabricated Sn-PSCs with FASnI(3)-DAMN perovskites showed enhanced PCE of 8.11% and a highly light soaking stable performance of over 300 h when measured under maximum power point tracking conditions.