A New Vinylene-Thiophene-Vinylene Linked Triphenylamine-Phenothiazine Unsymmetrical D-π-D Small Molecule: Defect Passivation and Hole Transporting Interfacial Layer for Perovskite Solar Cells

Abstract

Surface defects and the susceptibility of the perovskite absorber in the presence of moisture result in poor long-term device stability, eventually constricting its commercialization. To overcome these detrimental issues, herein we designed, synthesized, and introduced a multifunctional organic small molecule (GS1), configured upon triphenylamine linked with phenothiazine via π-linker vinylene-thiophene-vinylene, between the dual-cation perovskite absorber and the hole transport layer (HTL) spiro-OMeTAD. The incorporated interface material's unique extended conjugation and electron-donating ability, along with optimum energy level alignment, benefits in the hole extraction. Undercoordinated lead cations in the perovskite lattice structure were successfully passivated by the donation of lone pairs of electrons present in the GS1 molecule, and the superior film-forming properties significantly influence the charge carrier dynamics. The device composed of the GS1 hole-transporting interfacial layer delivers a lower leakage current, high shunt resistance, and reduced trap-state density as compared to the pristine device. Consequently, the device J−V parameters like short circuit current density (J sc ), fill factor (FF), and power conversion efficiency (PCE) show considerable improvement as compared to the pristine device. Superior thermal stability and hydrophobicity rendered by the GS1 molecule assist in preventing moisture ingress, which results in improved stability under high relative humidity conditions.

Minireview and Perspectives of Liquid Crystals in Perovskite Solar Cells

“…Owing to the remarkable optoelectronic properties, perovskites have sparked great research interest for solar cell applications during the past decade. − Since the first PSC was developed in 2009 by Kojima et al, there has been rapid improvement in terms of efficiency, which has been thoroughly documented in the literature. The efficiency of PSCs increased from 3.8 to 25.8% in the last 10 years, whereas other photovoltaic technologies required more than 20 years to achieve comparable efficiencies. − Meanwhile, on the basis of the Shockley–Queisser limit, the potential efficiency of PSC is greater than 30% .…”