Triphenylamine (TPA)‐Functionalized Structural Isomeric Polythiophenes as Dopant Free Hole‐Transporting Materials for Tin Perovskite Solar Cells

Abstract

A new series of triphenylamine (TPA)‐functionalized isomeric polythiophenes are developed as hole transporting materials (HTM) for inverted tin‐based perovskite solar cells (TPSCs). Bithiophene (BT) is first functionalized with two TPA (electron donor; D) at 3 and 5 positions to give two structural isomeric compounds (3BT2D and 5BT2D). The functionalized BT2Ds are then coupled with 3,3′‐bis(tetradecylthio)‐2,2′‐bithiophene (SBT‐14)/3,3′‐ditetradecyl‐2,2′‐bithiophene (BT‐14) to produce structural isomeric polythiophenes (1‐4), which are compared to conventional poly[N,N″‐bis(4‐butylphenyl)‐N,N″‐bis(phenyl)‐benzidine] (poly‐TPD) as HTMs for TPSCs. With the appropriate alignment of energy levels with regard to the perovskite layer, the TPA‐functionalized polymers‐based TPSCs exhibit enhanced operational stability and efficiency. Moreover, the long thiotetradecyl chain in SBT‐14 with intramolecular S(alkyl)∙∙∙S(thio) interactions restricts the molecular rotation and has a strong impact on the molecular solubility and wettability of the film during device fabrication. Among all the polymers studied, TPSCs fabricated with 3‐SBT‐BT2D polymer exhibit the highest hole mobility as well as the slowest charge recombination and achieve the highest power conversion efficiency of 8.6%, with great long‐term stability for the performance retaining ≈90% of its initial values for shelf storage over 4000 h, which is the best efficiency for non‐PEDOT:PSS‐based TPSCs ever reported.

Efficient quasi-2D tin perovskite solar cells based on mixed monoammonium and diammonium terminal molecules

“…1 Over the past decade, several seminal strategies have been employed to enhance the efficiency of tin perovskite solar cells (TPSCs) from approximately 6% to over 14%, 2–6 including compositional manipulation, 7–9 additive engineering, 10–13 surface modification 14,15 and device architecture design. 16–18…”

In-Situ Probing the Degradation Behavior of the Organic–Inorganic Hybrid Perovskite Film by Scanning Tunneling Microscopy

“…Solution-processed organic–inorganic hybrid perovskite (OIHP) films are promising materials for use in future photovoltaic devices. − The stability of OIHP films is one of the key issues to overcome compared with other competing commercial products. It has been observed that OIHP films are very sensitive to the environment conditions and can degrade quickly in the external environment such as light, temperature, etc., , decomposing into metal halides and gases .…”

4,4′-([2,2′-Bithiophene]-5,5′-diylbis(ethyne-2,1-diyl))bis(1-methylpyridin-1-ium) Iodide

“…The field of organic semiconductors [7,8], in particular, greatly profits from oligo-and polythiophenes, thanks to their optoelectronic properties, such as luminescence, charge carrier mobility and tunability of the HOMO-LUMO energy gap, which can be adjusted by varying both the number of thiophene subunits and the chemical nature and position of substituents on the heteroaromatic rings. For these reasons, some of the most investigated applications of oligo-and polythiophenes are represented by organic lightemitting diodes (OLEDs) [9], organic field-effect transistors (OFETs) [10], organic solar cells (OSCs) and other photovoltaic applications [11,12], and conductivity-based sensors and biosensors [13,14].…”