A Highly Planar Nonfullerene Acceptor with Multiple Noncovalent Conformational Locks for Efficient Organic Solar Cells

Abstract

A novel nonfullerene small‐molecular acceptor indacenodithiophene (IDT)‐4CN is designed and synthesized with IDT as the core and benzothiadiazole and dicyanoethxylrhodanine as end‐capping groups. Multiple noncovalent conformational locks N…S, CH…O, and CH…N are introduced into the backbone, resulting in a highly planar molecular acceptor. As a result, the IDT‐4CN‐based organic solar cells exhibit a power conversion efficiency of 8.13%, which is much higher than that of PC71BM‐based devices (6.19%). A novel method is thus demonstrated to construct highly planar molecular acceptors for organic solar cells.

Near‐Infrared Nonfullerene Acceptors Based on Benzobis(thiazole) Unit for Efficient Organic Solar Cells with Low Energy Loss

“…In this work, we choose benzobis(thiazole) (BBTz) and cyclopentadithiophene (CPDT) as molecular core and donor units, respectively, to check the above molecular design strategy. The BBTz unit was chosen for the design of nonfullerene acceptors, despite rarely utilized in photovoltaic materials, due to the following considerations: 1) S···N noncovalent interaction can be formed between the nitrogen atom of the BBTz unit and the sulfur atom of the CPDT unit to lock the molecular geometry, 2) the quinoid‐resonance effect of the BBTz unit can be utilized to narrow the bandgap of the nonfullerene acceptors, 3) the electron‐withdrawing property of BBTz unit can help lower the HOMO level. The D‐C‐D molecular structure is flanked by two different electron‐withdrawing terminals, (2‐(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1 H ‐inden‐1‐ylidene)malononitrile and 2‐(6‐oxo‐5,6‐dihydro‐4 H ‐cyclopenta[ c ]thiophen‐4‐ylidene)malononitrile), to check the effect of terminals on the device performance, thus resulting in two novel nonfullerene acceptors (X‐PCIC and X1‐PCIC) with similar properties in the absorption range and energy levels, but a significant difference in terminal packing strength.…”

Electron‐Deficient and Quinoid Central Unit Engineering for Unfused Ring‐Based A1–D–A2–D–A1‐Type Acceptor Enables High Performance Nonfullerene Polymer Solar Cells with High Voc and PCE Simultaneously

“…To the best of our knowledge, it is worth pointing that the PCE of 12.5% is the highest value for unfused A 1 –D–A 2 –D–A 1 ‐SMAs with the electron‐deficient unit as central A 2 unit in binary PSCs, and is also the highest PCE for unfused ring NF‐SMA‐based PSCs with a V oc > 0.9 V (see Scheme 1 and Table S1 in the Supporting Information). [ 53,57–59,62,63,69–73 ] These results reveal that the central electron‐deficient unit have significantly impact on the device performance and BT2FIDT‐4Cl with difluorobenzothiadiazole is a good choice to achieve highly efficient A 1 –D–A 2 –D–A 1 unfused ring NF‐SMAs with high V oc .…”

“…For the high performance (PCE > 12%) of unfused ring SMA‐based device, most of the corresponding V oc are distributed in the range of 0.85–0.89 V. [ 54,64,66,68,69 ] Once the V oc is further increased to over 0.90 V, the PCEs will drop sharply. [ 57,58,62,63,69–73 ] Thus, it is necessary to find more effective strategies to synthesize novel unfused ring NF‐SMAs to achieve both high V oc and high FF, simultaneously, thus improving the PCE.…”

Asymmetric Wide‐Bandgap Polymers Simultaneously Improve the Open‐Circuit Voltage and Short‐Circuit Current for Organic Photovoltaics

“…The maximum absorption peaks of PBDT‐F‐2TC and PBDT‐SF‐2TC in solutions are equal to those in films, locating at 540 and 542 nm, respectively. In addition, a weak shoulder peak is observed in both PBDT‐F‐2TC and PBDT‐SF‐2TC thin film, indicating the existence of weak intermolecular interaction in the copolymers . The absorption edge (λ onset ) of the PBDT‐F‐2TC and PBDT‐SF‐2TC are located at 629 and 626 nm, corresponding to an optical bandgap ( E g opt ) of 1.97 and 1.98 eV, respectively.…”