Molecular Configuration Engineering in Hole‐Transporting Materials toward Efficient and Stable Perovskite Solar Cells

Abstract

The development of hole-transporting materials (HTMs) that can passivate defects in perovskite is of great significance in improving the efficiency and long-term stability of perovskite solar cells. To date, the investigation on HTMs mainly focus on exploring new structures, while molecular configuration is seldomly concerned. In this work, two small molecules are developed as HTMs with benzil and phenanthrene quinone as the core structure, respectively. With similar structure and the same defect passivation groups, whereas, the two molecules exhibit different configurations, thus distinct properties. Compared to 3,6-bis(3,6-bis(bis(4-methoxyphenyl)amino)-9H-carbazol-9-yl) phenanthrene-9,10-dione (PQ) with a rigid core structure, the benzil group in 1,2-bis(4-(3,6-bis(bis(4-methoxyphenyl)amino)-9H-carbazol-9-yl)phenyl)ethane-1,2-dione (DB) is flexible and can adjust molecular configuration to efficiently interact with the underlying perovskite material, which is confirmed from both experimental results and theoretical simulations. The DB-based device exhibits a high power conversion efficiency of 22.21% with excellent long-term stability, superior to the PQ-based device (20.22%). This study demonstrates that molecular configuration engineering will directly affect the properties of hole transport materials, as well as their interactions with perovskite, which should also be taken into consideration when devising HTMs.

Conformation Tailoring of Diphenylfluorene‐Cored Isomers as Hole‐Transport Materials for Perovskite Solar Cells

“…In addition to the high‐energy spectral origin near 300 nm, the FH27 and FH99 respectively exhibit the dominant absorption peaks at 382 and 342 nm, which are originated from the localized π – π * electron transitions and intramolecular charge delocalization from the polyaromatic systems. [ 24 ] With respects to FH99, the FH27 sends an obvious bathochromic shift, suggesting its more disciplined couplings architecture and stronger intermolecular conjugation effects. [ 25 ] The cyclic voltammetry measurements (Figure S11, Supporting Information) are adopted to clarify the electrochemical features of HTMs, from which we can decide the HOMO energy levels for FH27 and FH99 are −5.29 and −5.25 eV, respectively.…”

Recent studies on small molecular and polymeric hole‐transporting materials for high‐performance perovskite solar cells

“…T A B L E 1 Summary of representative small molecular HTMs for PSCs reported in 2022. focused on molecular configuration engineering through the development of new HTMs with two different molecular configurations, one with a rigid phenanthrene quinone core structure (PQ) and the other with a flexible benzil core unit (DB). With a similar structure and the same defect passivation groups, the two molecules exhibit distinct properties, with DB-based PSCs exhibiting a PCE of 22.21% and having a molecular configuration that can be adjusted to efficiently interact with the underlying perovskite material [66].…”

Modulation of intermolecular interactions in hole transporting materials for improvement of perovskite solar cell efficiency: a strategy of trifluoromethoxy isomerization

“…In the molecular design of HTMs for PSCs, the main strategies include adjusting molecular structures, designing isomeric forms, and introducing functional groups. For example, Tang et al 10 considered the structure–property relationship and designed and synthesized two HTMs (PQ and DB) with similar molecular structures. Among them, DB, which has a core benzoyl structure, due to its flexible molecular structure, effectively interacts with the underlying perovskite, thereby enhancing the overall performance and stability of the devices.…”