13.34 % Efficiency Non‐Fullerene All‐Small‐Molecule Organic Solar Cells Enabled by Modulating the Crystallinity of Donors via a Fluorination Strategy

Abstract

Non-fullerene all-small-molecule organic solar cells (NFSM-OSCs) have shown potential as OSCs,o wing to their high purity,easy synthesis and good reproducibility.However, challenges in the modulation of phase separation morphology have limited their development. Herein, two novel small molecular donors,B TEC-1F and BTEC-2F,d erived from the small molecule DCAO3TBDTT,are synthesized. Using Y6 as the acceptor,d evices based on non-fluorinated DCAO3TBDTT showed an open circuit voltage (V oc )o f 0.804 Vand ap ower conversion efficiency (PCE) of 10.64 %. Mono-fluorinated BTEC-1F showed an increased V oc of 0.870 Va nd aP CE of 11.33 %. The fill factor (FF) of difluorinated BTEC-2F-based NFSM-OSC was improved to 72.35 %r esulting in aP CE of 13.34 %, whichi sh igher than that of BTEC-1F (61.35 %) and DCAO3TBDTT (60.95 %).To our knowledge,t his is the highest PCE for NFSM-OSCs. BTEC-2F had amore compact molecular stackingand alower crystallinity which enhanced phase separation and carrier transport.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Moving Alkyl‐Chain Branching Point Induced a Hierarchical Morphology for Efficient All‐Small‐Molecule Organic Solar Cells

“…Compared with the convenient interpenetration structure in the polymer systems, suitable size of nanofibrous domain in all small molecular systems is prerequisite which could supply favorable exciton separation and charge transport pathway. [ 22,24 ]…”

“…[ 16–21 ] However, small molecular donors normally possessed stronger crystallinity but a weaker ability to form interpenetrating network in all‐small‐molecule organic solar cells (ASM‐OSCs). [ 22–24 ] Lack of efficient charge transport channel would restrict the exciton diffusion, charge separation, and charge transport, which could interpret why the fill factor (FF) of ASM‐OSCs was not as high as that of polymer solar cells. [ 25–27 ] Therefore, tuning the morphology of the active layer is one of the most critical factors which need to be considered for the performance improvement for ASM‐OSCs.…”

“…[ 25–27 ] Therefore, tuning the morphology of the active layer is one of the most critical factors which need to be considered for the performance improvement for ASM‐OSCs. [ 7,22,28–30 ] For matching with the small molecular acceptors such as Y6, we reported a small molecular donor ZR1 based on dithieno[2,3‐d:2ʹ,3ʹ‐dʹ]benzo[1,2‐b:4,5‐bʹ]dithiophene (DTBDT) unit. Binary all‐small‐molecule OSC based on ZR1:Y6 blend achieved the highest efficiency of 14.34% by optimizing their hierarchical morphologies, in which the donor or acceptor rich domains with size up to ca.…”

Recent progress on all‐small molecule organic solar cells using small‐molecule nonfullerene acceptors

“…These unsatisfactory results mainly originate from the limited materials system and the hardly controlled morphology. While thanks to the innovation of NFAs as well as SMDs, we have witnessed impressive results with PCEs around 9% to 12% since 2017 35‐40 . Recently, Hou et al demonstrated an encouraging PCE of 15.3% (certified 15.1%) 41 for the binary devices.…”

Printable and Large‐Area Organic Solar Cells Enabled by a Ternary Pseudo‐Planar Heterojunction Strategy

“…Due to the advantages of simple preparation and good film quality, spin-coating has become the conventional method for preparing OSCs. [27][28][29][30][31] Unfortunately, in the process of preparing the active layer film by spin-coating, the active layer solution will be thrown out of the substrate, causing material waste. At the same time, as the effective area increases, the thickness of active layer film will be uneven because of the different forces at the substrate center and edges.…”