Dye‐Incorporated Polynaphthalenediimide Acceptor for Additive‐Free High‐Performance All‐Polymer Solar Cells

Abstract

All-polymer solar cells (all-PSCs) can offer unique advantages for applications in flexible devices, and naphthalene diimide (NDI)-based polymer acceptors are the widely used polymer acceptors. However, their power conversion efficiency (PCE) still lags behind that of state-of-the-art polymer solar cells, due to low light absorption, suboptimal energy levels and the strong aggregation of the NDI-based polymer acceptor. Herein, a rhodanine-based dye molecule was introduced into the NDI-based polymer acceptor by simple random copolymerization and showed an improved light absorption coefficient, an up-shifted lowest unoccupied molecular orbital level and reduced crystallization. Consequently, additive-free all-PSCs demonstrated a high PCE of 8.13 %, which is one of the highest performance characteristics reported for all-PSCs to date. These results indicate that incorporating a dye into the n-type polymer gives insight into the precise design of high-performance polymer acceptors for all-PSCs.

High‐performing random terpolymer‐based nonfullerene polymer solar cells fabricated using solvent additive‐free as‐cast blend films

“…The 3MTB and 3MTT :ITIC blends also displayed a strong (010) diffraction of the π–π stacking in the out‐of‐plane profiles. The data indicate that the terpolymer chains in the blend films predominantly adopted the face‐on orientation on the substrate, which is similar to the diffraction data for the 3MT‐Th :ITIC blend film . Such a polymer chain arrangement can lead to excellent charge transport phenomena in a vertically stacked PSC.…”

“…Over the past few years, random terpolymers bearing one donor and two different acceptors (or one acceptor and two different donors) having conjugated polymer backbones have emerged as promising materials with many advantages over electron‐donating binary copolymers owing to the ability to fine‐tune the internal morphology of the active layer, solubility, absorption range, energy levels, and polymer chain orientation of the former in blend films . Therefore, highly efficient nonfullerene PSCs can be realized by using specific terpolymer systems and simple device fabrication processes.…”

“…In our previous study, 3MT‐Th bearing benzodithiophene (BDT) and methyl‐3‐thiophenecarboxylate (3MT) showed high efficiency in an as‐cast film‐based non‐fullerene PSC . Compared to strongly electron‐deficient monomers, 3MT is a relatively weak acceptor and has asymmetric structure giving less rigidity of polymer backbone.…”

Imide‐Functionalized Polymer Semiconductors

“…By introducing a rhodamine derivative dye into the side chain, the absorption coefficient of the resulting terpolymers was greatly increased, leading to a more efficient photon capturing and thus an increased J sc . Moreover, the dye incorporation raised the LUMO levels of the terpolymers, resulting in higher V oc (0.85 V), which combined with the proper phase separation and much more balanced μ h,SCLC / μ e,SCLC value, afforded a high PCE of 8.13 % …”

Recent Progress in All‐Polymer Solar Cells Based on Wide‐Bandgap p‐Type Polymers

“…Therefore, the all‐PSCs device based on PBDB‐T:PNDI‐Si25 exhibited a PCE of 7.4 %. Recently, Chen and co‐workers partially introduced a rhodanine‐based dye into the side chain of thiophene to acquire two novel NDI‐based polymer acceptors, namely, PNDI‐2T‐TR(5) and PNDI‐2T‐TR(10) . Compared to the reference polymer N2200, the dye molecules‐modified polymers exhibited enhanced absorbance coefficient and up‐shifted LUMO levels, resulting in both higher J SC and V OC .…”