Polyacrylic Acid Grafted Carbon Nanotubes for Immobilization of Lead(II) in Perovskite Solar Cell

In this report, we propose a concept of lead immobilization to suppress the lead exposure risk by employing poly(acrylic acid) grafted carbon nanotubes (CNT-PAA) as dopants in the preparation of perovskite thin films. Due to the presence of a large amount of carboxyl groups and the self-bundling of water insoluble CNTs, the CNT-PAA exhibited a high Pb²⁺-immobilization capability, allowing them to retain the lead components on the substrates and reduce lead(II) leaching below the hazardous waste limit once occasionally exposed to water. Moreover, the PAA chains on the CNTs surface can strongly chelate with Pb²⁺ to accelerate crystal nucleation in precursor solution and to passivate undercoordinated defects in the as-achieved thin films, and the inserted CNTs within the perovskite grains can regulate the perovskite growth with vertical orientation and boost both electron and hole mobility, resulting in eliminated nonradiative recombination and facilitated charge transport across the perovskite layer.