Narrow bandgap n‐type organic semiconductors (n‐OS) have attracted great attention in recent years as acceptors in organic solar cells (OSCs), due to their easily tuned absorption and electronic energy levels in comparison with fullerene acceptors. Herein, a new n‐OS acceptor, Y5, with an electron‐deficient‐core‐based fused structure is designed and synthesized, which exhibits a strong absorption in the 600–900 nm region with an extinction coefficient of 1.24 × 105 cm−1, and an electron mobility of 2.11 × 10−4 cm2 V−1 s−1. By blending Y5 with three types of common medium‐bandgap polymers (J61, PBDB‐T, and TTFQx‐T1) as donors, all devices exhibit high short‐circuit current densities over 20 mA cm−2. As a result, the power conversion efficiency of the Y5‐based OSCs with J61, TTFQx‐T1, and PBDB‐T reaches 11.0%, 13.1%, and 14.1%, respectively. This indicates that Y5 is a universal and highly efficient n‐OS acceptor for applications in organic solar cells.

Recently, indoor photovoltaics have attracted much interest for their ability to power small electronic devices and sensors, especially with the growth of the Internet of Things (IoT). Due to their absorption covering ambient emission spectra and tunable electronic structures, π-conjugated polymers and small molecules are well-suited for these applications. Among many benefits, including their ink processability, lightweight and flexibility; indoor organic photovoltaics (IOPVs) show power conversion efficiencies (PCE) over 26%. It represents a power output over 30 μW cm -2 under office light (500 lux), which is sufficient to operate many electronic devices and sensors with a relatively small photovoltaic area. This focus review highlights the major advances in the material design for IOPVs and includes some industrial insights to reach the production scale criteria.''Internet of Things'' over the last decades. Data were taken from Web of Science database on January 6 th , 2020.

Organic solar cells (OSCs) have progressed rapidly in the recent years through the development of novel organic photoactive materials, especially non-fullerene acceptors (NFAs). Consequently, OSCs based on state-of-the-art NFAs have...

Organic photovoltaics have attracted much attention in the past few years, mainly due to their ability to be fully printed at low cost and large scale. However, the organic semiconductors utilized as the active layer are typically synthesized using Migita−Stille or Suzuki−Miyaura cross-coupling, which is not cost efficient and may bring toxicity concerns. In the search for atom-economical synthesis, direct (hetero)arylation polymerization (DHAP) enables the activation of aromatic C−H bonds, both reducing synthetic steps of monomers and toxic reaction byproducts. In this issue, we will discuss the recent contributions on direct (hetero)arylation synthesis toward mass production of photovoltaic materials. The impact of DHAP on material efficiency will be addressed and compared to conventional coupling methods. The ongoing improvements will be discussed, as DHAP becomes more sustainable at higher scale and materials are observed as having higher quality.

The environmental impact of solution processed organic solar cells (OSCs) can be mitigated by introducing so‐called green solvents during the fabrication processes. However, the effects of such green solvents on the molecular‐level structures and optoelectronic properties lack in‐depth characterization. Here, insights into the structure–processing–property correlation of a PPDT2FBT:PC61BM bulk‐heterojunction (BHJ) system processed from a green solvent, ortho‐xylene (o‐XY), is investigated in comparison with the same blend processed from a traditional halogenated solvent, chlorobenzene (CB). The BHJ blends are characterized with various techniques probing at difference length scales, and an increased donor:acceptor (D:A) interfacial area as well as well‐mixed features in the bulk morphologies of the active layer are observed for the o‐XY processed BHJ blend. Furthermore, molecular‐level differences in the D–A intermolecular interactions at the BHJ interfaces in o‐XY and CB cast films are elucidated by 2‐dimensional solid‐state nuclear magnetic resonance (ssNMR) measurements and analysis. These results are consistent with the device properties, suggesting that the green‐solvent‐processed devices have longer charge carrier lifetimes and faster charge carrier extraction. The optimized PPDT2FBT:PC61BM devices processed from o‐XY can achieve a noteworthy higher power conversion efficiency (PCE) owing to a higher short‐circuit current density and fill factor.