Chemical Bridge-Mediated Heterojunction Electron Transport Layers Enable Efficient and Stable Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) emerged as potential photovoltaic energy-generating devices developing in recent years because of their excellent photovoltaic properties and ease of processing. However, PSCs are still reporting efficiencies much lower than their theoretical limits owing to various losses caused by the charge transport layer and the perovskite. In this regard, herein, an interface engineering strategy using functional molecules and chemical bridges was applied to reduce the loss of the heterojunction electron transport layer. As a functional interface layer, ethylenediaminetetraacetic acid (EDTA) was introduced between PCBM and the ZnO layer, and as a result, EDTA simultaneously formed chemical bonds with PCBM and ZnO to serve as a chemical bridge connecting the two. DFT and chemical analyses revealed that EDTA can act as a chemical bridge between PCBM and ZnO, passivate defect sites, and improve charge transfer. Optoelectrical analysis proved that EDTA chemical bridge-mediated charge transfer (CBM-CT) provides more efficient interfacial charge transport by reducing trap-assisted recombination losses at ETL interfaces, thereby improving device performance. The PSC with EDTA chemical bridge-mediated heterojunction ETL exhibited a high PCE of 21.21%, almost no hysteresis, and excellent stability to both air and light.

Oxysalt based synergistic dual interfacial engineering for high performance p–i–n structured perovskite solar cells

“…These results indicate that there is an up-shift in the quasi-Fermi level, which is consistent with previous reports. 14,46 This trend was in line with the work-function change obtained by UPS analysis (Fig. 3d).…”

“…48,49 The characteristic –CN symmetric stretch around ∼1700 cm −1 of perovskite shifted to a lower wavenumber along with reduced intensity, thus indicating the possibility of bonding between the lone pair of electrons available on nitrate ions with perovskite via coordination bonding. 46 Furthermore, a small peak appeared around 1341.13 cm −1 with a lower wavenumber shift from its original value (∼1383 cm −1 ) in the sodium nitrate-treated samples, thus indicating interaction of nitrate ions on the perovskite surface (Fig. 3f).…”