Multifunctional Graphdiyne Enables Efficient Perovskite Solar Cells via Anti-Solvent Additive Engineering

Abstract

Finding ways to produce dense and smooth perovskite films with negligible defects is vital for achieving high-efficiency perovskite solar cells (PSCs). Herein, we aim to enhance the quality of the perovskite films through the utilization of a multifunctional additive in the perovskite anti-solvent, a strategy referred to as anti-solvent additive engineering. Specifically, we introduce ortho-substituted-4′-(4,4″-di-tert-butyl-1,1′:3′,1″-terphenyl)-graphdiyne (o-TB-GDY) as an AAE additive, characterized by its sp/sp2-cohybridized and highly π-conjugated structure, into the anti-solvent. o-TB-GDY not only significantly passivates undercoordinated lead defects (through potent coordination originating from specific high π–electron conjugation), but also serves as nucleation seeds to effectively enhance the nucleation and growth of perovskite crystals. This markedly reduces defects and non-radiative recombination, thereby increasing the power conversion efficiency (PCE) to 25.62% (certified as 25.01%). Meanwhile, the PSCs exhibit largely enhanced stability, maintaining 92.6% of their initial PCEs after 500 h continuous 1-sun illumination at ~23 °C in a nitrogen-filled glove box.

1. Introduction

FAPbI3-based perovskite solar cells (PSCs) have drawn tremendous attention during the past decade and reached certified efficiencies of 26.7% in single-cell devices [1]. Such remarkable progress mainly comes from improvements in perovskite film quality [2–16]. Among the various methods capable of producing high-quality perovskite films, the one-step deposition process is especially appealing for industrial production due to its simplicity and cost-effectiveness. Initially, the conventional one-step deposition process had several critical drawbacks, including poor film coverage on the substrate due to challenges in controlling perovskite nucleation and crystallization [17, 18]. The anti-solvent approach was subsequently developed, wherein anti-solvents like toluene and chlorobenzene were dropped on the substrate during spin-coating of perovskite precursors [19, 20]. This process extracts residual solvents from the perovskite film almost instantaneously, resulting in uniform and smooth films with minimal pinholes.

However, such solution-processed polycrystalline perovskite films still present abundant defects, such as undercoordinated Pb2+ and halide (I−) ions, leading to serious non-radiative recombination and uncompetitive device performance [21–23]. To address this issue, various effective additives have been incorporated into the perovskite precursor solution to control crystallization [24, 25]. Nevertheless, it is still a significant challenge to simultaneously achieve surface passivation and improved perovskite grain growth. Thus, a promising approach known as anti-solvent additive engineering (AAE) has been introduced. Specifically, functional additives, such as 2-hydroxyethyl faacrylate (HEA), 2-amidinopyrimidine hydrochloride (APC) and lead(II) 2-ethylhexanoate (LDE), have been added into the anti-solvent [26–28]. Although AAE has shown promise, there are currently few reports on AAE-based PSCs, and only a limited number of additives have been explored.

Graphdiyne (GDY), as a branch of the 2D carbon family, possesses sp/sp2-cohybridized and highly π-conjugated structure [29]. Owing to this unique structure, GDY exhibits high carrier mobility, a tunable band gap and strong light absorption, and has been widely applied in optoelectronics [30–34]. Nonetheless, in-depth investigations into GDY-regu...