An alternating copolymer of phenothiazine and ethylenedioxythiophene for perovskite solar cells: effects of flexible and rigid substituent alternation.

Developing p-type polymeric semiconductors with exceptional electrical performance, heat tolerance, and cost-effectiveness is pivotal for advancing the practical application of n-i-p perovskite solar cells. Here, we employed direct arylation polycondensation to synthesize an alternating copolymer of phenothiazine and 3,4-ethylenedioxythiophene, featuring a high glass transition temperature (175 °C). In addition to the alternation of conjugated units within the main chain, the copolymer features alternating flexible (2-octyldodecyl) and rigid (trimethylphenyl) substituents at the nitrogen positions of the phenothiazine moiety. Compared to reference polymers with solely flexible or rigid substituents, the alternating use of these moieties resulted in the polymeric semiconductor composite film with smoother morphology and enhanced hole mobility. By employing this polymer with a distinct distribution of substituents and an innovative main chain structure as a hole transport material, we fabricated perovskite solar cells achieving an average efficiency of 25.1%. These cells also exhibited excellent stabilities under conditions of 85 °C thermal storage and 45 °C operation.

An Oxa[5]helicene-Based Racemic Semiconducting Glassy Film for Photothermally Stable Perovskite Solar Cells.

Attaining the durability of high-efficiency perovskite solar cells (PSCs) operated under concomitant light and thermal stresses is still a serious concern before large-scale application. It is crucial to maintain the phase stability of the organic hole-transporting layer for thermostable PSCs across a range of temperatures sampled during device operation. To address this issue, we propose a racemic semiconducting glassy film with remarkable morphological stability, exemplified here by a low-molecular symmetry oxa[5]helicene-centered organic semiconductor (O5H-OMeDPA). The helical configuration of O5H-OMeDPA confers the trait of multiple-dimension charge transfer to the solid, resulting in high hole mobility of 6.7 × 10-4 cm2 V-1 s-1 of a solution-processed glassy film. O5H-OMeDPA is combined with a triple-cation dual-halide lead perovskite to fabricate PSCs with power conversion efficiencies of 21.03%, outperforming the control cells with spiro-OMeTAD (20.44%). Moreover, the cells using O5H-OMeDPA exhibit good long-term stability during full-sunlight soaking at 60°C.

A peri-Xanthenoxanthene Centered Columnar-Stacking Organic Semiconductor for Efficient, Photothermally Stable Perovskite Solar Cells.

Modulating the structure and property of hole-transporting organic semiconductors is of paramount importance for high-efficiency and stable perovskite solar cells (PSCs). This work reports a low-cost peri-xanthenoxanthene based small-molecule P1, which is prepared at a total yield of 82 % using a three-step synthetic route from the low-cost starting material 2-naphthol. P1 molecules stack in one-dimensional columnar arrangement characteristic of strong intermolecular π-π interactions, contributing to the formation of a solution-processed, semicrystalline thin-film exhibiting one order of magnitude higher hole mobility than the amorphous one based on the state-of-the art hole-transporter, 2,2-7,7-tetrakis(N,N'-di-paramethoxy-phenylamine 9,9'-spirobifluorene (spiro-OMeTAD). PSCs employing P1 as the hole-transporting layer attain a high efficiency of 19.8 % at the standard AM 1.5 G conditions, and good long-term stability under continuous full sunlight exposure at 40 °C.

N-Annulated Perylene-Based Hole Transporters for Perovskite Solar Cells: The Significant Influence of Lateral Substituents.

Perylene derivatives are a family of well-known organic electron-transporting materials with excellent photochemical and thermal stabilities, and have been widely used in various optoelectronic devices. In this work, two diphenylamine functionalized N-annulated perylenes are reported as hole-transporting materials (HTMs) for perovskite solar cells. Through joint theoretical and experimental studies, the HTM employing a methoxyphenyl lateral substituent is found to feature a closer stacking distance and better aggregate connectivity in the solid film than its analogue with the bulky 2-hexyldecyl lateral substituent, contributing to a higher hole mobility and a remarkably enhanced device performance of perovskite solar cells. This work demonstrates the significant influence of lateral substituents of HTMs on the intermolecular packing and solid microstructure, giving a clear insight on the molecular design of high-performance organic semiconductors.

Facile Preparation of α-Cyano-α,ω-Diaryloligovinylenes: A New Class of Color-Tunable Solid Emitters.

An efficient Knoevenagel condensation reaction was used to construct a series of α-cyano-α,ω-diaryloligovinylenes, which show prominent fluorescence emission in the solid state. On investigating the effect of conjugation length on fluorescent properties, we found that the diene structure showed superior solid-state luminescence. Furthermore, the emission color could be adjusted by introducing donor or acceptor functional groups at the terminal aryl groups. Full-color emission in the visible region can be achieved by adding different functional groups to the α-cyano-α,ω-diaryldivinylene moiety. The structure-property relationships were elucidated and some observations such as the substitution position effects were discussed. These compounds have potential applications as full-color solid emissive candidates in material science and their simple structures allow them to be easily modified resulting in further interesting properties.