Defect‐Passivating and Stable Benzothiophene‐Based Self‐Assembled Monolayer for High‐Performance Inverted Perovskite Solar Cells

Abstract

Effective passivation of defects at the buried interface between the perovskite absorber and hole‐selective layer (HSL) is crucial for achieving high performance in inverted perovskite solar cells (PSCs). Additionally, the HSL needs to possess compact molecular packing and intrinsic photo‐ and thermo‐stability to ensure long‐term operation of the devices. In this study, a novel MeO‐BTBT‐based self‐assembled monolayer (SAM) is reported to serve as an efficient HSL in inverted PSCs. Compared to the well‐established carbazole‐containing SAM MeO‐2PACz, MeO‐BTBT has flat and more extended conjugation with large atomic radius of the sulfur atom. These induce stronger intermolecular interactions to enable more ordered and compact SAM to be formed on indium–tin oxide (ITO) substrates. Meanwhile, the sulfur atoms in MeO‐BTBT can coordinate with Pb2+ ions to passivate the defects at the buried interface of perovskite absorber. The derived perovskite films show both high photoluminescence (PL) quantum yield (13.2%) and a long lifetime (7.2 µs). The PSCs based on MeO‐BTBT show a PCE of 24.53% with an impressive fill factor of 85.3%. The PCEs of MeO‐BTBT‐based devices can maintain ≈95% of their initial values after being aged at 65 °C for more than 1000 h or continuous operation under 1‐sun illumination.

Management of the π-Conjugated System in Carbazole–Diphenylamine Derivative-Based Hole-Transporting Materials for Perovskite Solar Cells: Theoretical Simulation and Experimental Research

“…With the increase in side-chain conjugated π systems, the μ values gradually increase, which can facilitate the induced dipole interactions between molecules and promote hole transfer. 31,32 For the simulated frontier molecular orbitals (FMOs), the highest occupied molecular orbitals (HOMOs) of CY3−CY5 are primarily located on the carbazole−diphenylamine unit, while the lowest occupied molecular orbitals (LUMOs) transition from a fully distributed state on the side-chain unit of CY3 to predominantly delocalized anthracene units in CY5 (Figure 2a). The effective separation of HOMO and LUMO in CY5 promotes intramolecular charge transfer (ICT).…”

“…As shown in Figure a, the calculated dipole moments (μ) for CY3, CY4, and CY5 are 1.38, 2.35, and 2.38 D, respectively. With the increase in side-chain conjugated π systems, the μ values gradually increase, which can facilitate the induced dipole interactions between molecules and promote hole transfer. , …”

Structural divergence of molecular hole selective materials for viable p-i-n perovskite photovoltaics: a comprehensive review

“…Jen et al introduced 7-methoxybenzo[ b ]benzo[4,5]thieno[2,3- d ]thiophene as the head group that connected to the phosphonic acid anchoring segment via a butyl linker to form MeOBTBT ( G32 ). 233 This material possessed a dipole moment of 2.8 D, which was higher than that of commonly employed MeO-2PACz (1.5 D) that assisted in a deeper work function of 4.72 eV for the former than the latter (4.61 eV). The presence of sulfur atoms passivates the uncoordinated lead ions, as evident from the decreased Pb 2+ binding energy due to electron sharing between the MeO-BTBT sulfur atom in the head group and Pb 2+ that assisted in the formation of a larger perovskite crystal grain size (≈600 nm).…”