Molecular Design and Cost-Effective Synthesis of Tetraphenylethene-Based Hole-Transporting Materials for Hybrid Solar Cell Application

Abstract

The innovative choice of core and periphery groups for organic hole-transporting materials (HTMs) has gained more attention for modern development in hybrid organic–inorganic perovskite solar cells (PSCs). For large-scale application of PSCs, the replacement of 2,2′,7,7′-tetrakis­(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD) has its demands such as low stability, high cost, and multistep synthesis. This has necessitated the introduction of novel cost-effective HTMs. Hence, at first, we obtained a theoretical design of tetraphenylethene (TPE)-based HTMs through the Gaussian method, which exhibits a substantial highest occupied molecular orbital energy level as compared with the perovskite. Further, the photophysical, electrochemical, and thermal properties were meticulously investigated with the aid of both experimental and computational methods. In order to enhance the solubility of HTMs in chlorobenzene, the methoxy-substituted phenyl group was replaced with the hexyloxy-substituted phenyl group, and also, the higher extent of solubility is recognized after the functional group exchanges. The power conversion efficiencies of TOHE and TOME are η = 13.96%, J sc = 21.00 mA/cm2, and V oc = 0.93 (V) and η = 6.83%, J sc = 13.45 mA/cm2, and V oc = 0.97 (V), respectively (under full sunlight AM 1.5G, 100 mW cm–2 irradiation). Moreover, the synthesis of highly stable TOHE involves a simple and cost-effective synthetic procedure, proving to be the most promising lead for designing efficient organic–inorganic hybrid solar cells.

Aggregation‐induced Emission Materials for High‐efficiency Perovskite Solar Cells

“…They discovered the fused tetraphenylethylene HTMs exhibited relatively higher quenching efficiency than exhibited relatively better device performance than the nonfused bifluorenylidene (FTPE-1 and FTPE-2), undoubtedly providing a new idea for designing the structure of the hole transport materials. Muniyasamy et al [43] designed three tetraphenylethene (TPE)-based HTMs through the Gaussian method, named (1) 1,1,2,2-tetrakis(4'-methoxy-[1,1'-biphenyl]-4-yl)ethene (TOME), (2) 1,1,2,2-tetrakis(4-(4-methoxy-5,6,7,8-tetrahydronaphthalen-1yl)phenyl)ethane (TOMEC) and (3) 4-hexyloxy phenyl as a donor [1,1,2,2-tetrakis(4'-(hexyloxy)-[1,1'-biphenyl]-4-yl)ethene (TOHE) (Figure 6c). The THOE-and TOME-modified perovskite films showed higher PL quenching efficiencies, indicating an efficient hole transfer yield (65 % and 96 %), which yielded 13.96 % and 6.83 % PCE of PSCs with TOME and TOHE.…”

“…The HTMs along with the TPE derivatives exhibited versatile features such as an easily available starting materials, a good hole mobility by the π-π conjugated structure and a peculiar electron donating potential for faster intramolecular charge transfer, further suppressing the carrier recombination, as illustrated in Figure 5. [43] There were many defects among perovskites particles in the PSCs without TPE derivatives-based HTMs, resulting in a serious charge carrier recombination at the interface. After introducing the TPE derivatives-based HTMs, more photogenerated electrons and holes were produced.…”

Exploring Acceptor Modification in Helicene‐Phenylamine‐Based Small Molecules for Organic and Perovskite Solar Cells

“…[39][40][41] The E g is intimately associated with open circuit voltage, dynamic stability, chemical reactivity, charge transport properties, softness, chemical reactivity, power conversion efficiency of the chromophores. [41][42][43][44][45] The FMOs offer a systematic route to determine the charge mobility and transmission within the parent and designed molecules. The FMO energy levels significantly influence charge transportation, optoelectronic characteristics, the working efficiency of OSCs and PSCs.…”

Additive Engineering for Mixed Lead–Tin Narrow-Band-Gap Perovskite Solar Cells: Recent Advances and Perspectives

“…The new third-generation solar cells, such as perovskite solar cells (PSCs), dye-sensitized solar cells, and quantum dot solar cells, have received increasing interests recently as a result of the facile fabrication process, low-cost raw material, and superior theoretical PCEs. − In particular, PSCs with lead (Pb)-based halide perovskites as light absorbers exhibit several unique and excellent optical/electronic properties, including adjustable band gaps, high optical absorption coefficients, high mobility, and long diffusion length of charge carriers, leading to a rapid boosting rate of PCEs of PSCs from 3.8 to 25.7% in the last 14 years. − Therefore, the newly developed PSCs are considered as the most potential replacements to traditional silicon-based solar cells for large-scale and sustainable photovoltaic power generation. , Although the PCEs of Pb-based PSCs have reached 25.7% recently, the large-scale applications of Pb-based organic–inorganic hybrid PSCs still face many crucial challenges. − First, the band gaps of Pb-based organic–inorganic perovskites currently used in high-performance PSCs are generally 1.5–1.6 eV, which are much larger than the theoretical optimal band gap of 1.3–1.4 eV for solar cells calculated according to the Shockley–Queisser (S–Q) theory . Second, the toxicity of Pb is extremely harmful to the environment and humans. − To overcome these problems, numerous researchers are trying to develop new Pb-free or Pb-less halide perovskites using non-toxic metals, including tin (Sn), bismuth (Bi), and germanium (Ge), to achieve sustainable and clean perovskite photovoltaics. − Among various alternatives to Pb 2+ cations, Sn 2+ cations have similar electronic structures to Pb 2+ and comparable ion radii (the ionic radii of Sn 2+ and Pb 2+ are 110 and 119 pm, respectively). − Therefore, partial or complete replacement of Pb 2+ in perovskites by Sn 2+ will not lead to significant lattice distortions in the perovskite structure . In addition, the band gaps of Pb–Sn perovskites can be easily adjusted between 1.17 and 1.55 eV by tailoring the Sn/Pb ratios, thereby extending the sunlight absorption range of Pb–Sn perovskites to the near-infrared region .…”