High‐Performance All‐Polymer Solar Cells Enabled by an n‐Type Polymer Based on a Fluorinated Imide‐Functionalized Arene

Abstract

A novel imide‐functionalized arene, di(fluorothienyl)thienothiophene diimide (f‐FBTI2), featuring a fused backbone functionalized with electron‐withdrawing F atoms, is designed, and the synthetic challenges associated with highly electron‐deficient fluorinated imide are overcome. The incorporation of f‐FBTI2 into polymer affords a high‐performance n‐type semiconductor f‐FBTI2‐T, which shows a reduced bandgap and lower‐lying lowest unoccupied molecular orbital (LUMO) energy level than the polymer analog without F or with F‐functionalization on the donor moiety. These optoelectronic properties reflect the distinctive advantages of fluorination of electron‐deficient acceptors, yielding “stronger acceptors,” which are desirable for n‐type polymers. When used as a polymer acceptor in all‐polymer solar cells, an excellent power conversion efficiency of 8.1% is achieved without any solvent additive or thermal treatment, which is the highest value reported for all‐polymer solar cells except well‐studied naphthalene diimide and perylene diimide‐based n‐type polymers. In addition, the solar cells show an energy loss of 0.53 eV, the smallest value reported to date for all‐polymer solar cells with efficiency > 8%. These results demonstrate that fluorination of imide‐functionalized arenes offers an effective approach for developing new electron‐deficient building blocks with improved optoelectronic properties, and the emergence of f‐FBTI2 will change the scenario in terms of developing n‐type polymers for high‐performance all‐polymer solar cells.

10.13% Efficiency All‐Polymer Solar Cells Enabled by Improving the Optical Absorption of Polymer Acceptors

“…However, most of the efficient all‐PSCs have PCEs ranging in 8–10%, although a few of them achieved PCEs over 11%, which is still far behind that of the efficient PSCs based on SM acceptors due to the lack of high‐performance polymer acceptors. To date, polymer acceptors have been mainly confined into a small number of structural building blocks, and the most widely studied one is the polymer N2200 with a donor–acceptor (D–A) backbone of naphthalene diimide (NDI)‐ alt ‐bithiophene due to its NBG and suitable molecular energy levels . However, N2200 neat film suffers from a low absorption coefficient of ≈0.3 × 10 5 cm −1 and an excess strong crystallinity and stacking, which usually lead to the limited photocurrent and large phase separation in active layers …”

“…Regarding such SM acceptor‐based PSCs, the all‐polymer solar cells (all‐PSCs) consisting of a polymer donor and a polymer acceptor show unique advantages in the flexible large‐scale and wearable energy generators due to their excellent morphology stability and mechanical robustness . However, most of the efficient all‐PSCs have PCEs ranging in 8–10%, although a few of them achieved PCEs over 11%, which is still far behind that of the efficient PSCs based on SM acceptors due to the lack of high‐performance polymer acceptors. To date, polymer acceptors have been mainly confined into a small number of structural building blocks, and the most widely studied one is the polymer N2200 with a donor–acceptor (D–A) backbone of naphthalene diimide (NDI)‐ alt ‐bithiophene due to its NBG and suitable molecular energy levels .…”

Alloy-like ternary polymer solar cells with over 17.2% efficiency

“…Single bulk heterojunction polymer solar cells (PSCs) have achieved dramatic progress through material evolution, device fabrication optimization and working mechanism exploration [1][2][3][4][5][6][7][8][9]. The power conversion efficiency (PCE) of PSCs has already exceeded 16% with narrow band gap nonfullerene material Y6 as acceptor [10][11][12][13][14].…”

Triimide‐Functionalized n‐Type Polymer Semiconductors Enabling All‐Polymer Solar Cells with Power Conversion Efficiencies Approaching 9%

“…Among various n‐type organic semiconductors, imide‐functionalized polymers show superior performance in various organic electronic devices, exemplified by the state‐of‐the‐art naphthalene diimide (NDI)‐ alt ‐bithiophene copolymer, a.k.a. N2200 .…”