Intrinsically Stretchable, Highly Efficient Organic Solar Cells Enabled by Polymer Donors Featuring Hydrogen‐Bonding Spacers

Abstract

Intrinsically stretchable organic solar cells (IS‐OSCs), consisting of all stretchable layers, are attracting significant attention as a future power source for wearable electronics. However, most of the efficient active layers for OSCs are mechanically brittle due to their rigid molecular structures designed for high electrical and optical properties. Here, a series of new polymer donors (PDs, PhAmX) featuring phenyl amide (N1,N3‐bis((5‐bromothiophen‐2‐yl)methyl)isophthalamide, PhAm)‐based flexible spacer (FS) inducing hydrogen‐bonding (H‐bonding) interactions is developed. These PDs enable IS‐OSCs with a high power conversion efficiency (PCE) of 12.73% and excellent stretchability (PCE retention of >80% of the initial value at 32% strain), representing the best performances among the reported IS‐OSCs to date. The incorporation of PhAm‐based FS enhances the molecular ordering of PDs as well as their interactions with a Y7 acceptor, enhancing the mechanical stretchability and electrical properties simultaneously. It is also found that in rigid OSCs, the PhAm5:Y7 blend achieves a much higher PCE of 17.5% compared to that of the reference PM6:Y7 blend. The impact of the PhAm‐FS linker on the mechanical and photovoltaic properties of OSCs is thoroughly investigated.

Correlation of Local Isomerization Induced Lateral and Terminal Torsions with Performance and Stability of Organic Photovoltaics

“…The performance of organic photovoltaics (OPVs) can be easily tuned by tailoring the chemical structures of organic components in the photoactive layer. − Since the first report of A-DA′D-A-type non-fullerene acceptors (NFAs), − the power conversion efficiencies (PCEs) of OPVs have been rapidly improved to greater than 19%. − This significant progress is mainly due to the delicate modifications of NFA structures. In general, there are two strategies in modifying NFAs, tailoring of the aromatic heterocycles in the conjugated backbone and tuning the aliphatic/aromatic side-groups. − The main efforts have been devoted to enhancing the molecular planarity for improving the light absorption and electron mobility of NFAs. − The additional halogenation on either π-core or terminal groups can further modulate the frontier molecular orbitals and the molecular packing/aggregation properties of NFAs. − …”

Large-Area Nonfullerene Organic Photovoltaic Modules with a High Certified Power Conversion Efficiency

“…A high power conversion efficiency (PCE) has been demonstrated for small-area devices, recently demonstrating a high chance of being commercialized in the future. − The improvement in PCE mainly relies on the innovation of active layer materials and the improvement of interfacial layers. Newly developed nonfullerene acceptors with strong absorption in the visible range have boosted device performance for small areas below 1 cm 2 . − The morphological stability in blend films was also improved by introducing the nonfullerene material system . The introduction of interfacial layers was also demonstrated to be beneficial for device stability and performance. − By selecting appropriate interfacial layers, the energy level alignment at the electrode/active layer interfaces and the built-in electric field can be tailored to enhance the collection efficiency.…”

Heterostructure Engineering of Solution-Processable Semiconductors for Wearable Optoelectronics

“…Lastly, new molecular designs of donors and acceptors have successfully improved the stretchability and PCEs in OPVs. A recent report showed that a donor molecule with flexible spacers could achieve great stretchability in an OPV with a PCE of 12.73%, a record efficiency in stretchable OPVs . The PCE retention is over 80% under ∼30% strain.…”