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,a nd naphthalene diimide (NDI)-based polymer acceptors are the widely used polymer acceptors.H owever,t heir power conversion efficiency (PCE) still lags behind that of state-of-the-art polymer solar cells,d ue to lowl ight absorption, suboptimal energy levels and the strong aggregation of the NDI-based polymer acceptor.H erein, ar hodanine-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,a dditive-free all-PSCs demonstrated ah igh PCE of 8.13 %, which is one of the highest performance characteristics reported for all-PSCs to date.T hese results indicate that incorporating ad ye into the n-type polymer gives insight into the precise design of high-performance polymer acceptors for all-PSCs.Polymer solar cells (PSCs) have made considerable progress during the past two decades. [1][2][3] Thep ower conversion efficiency (PCE) of single-junction fullerene-based PSCs has been attained over 11 %. [4] Recently,P CEs exceeding 13 % have been achieved with proper molecular designs of wideband-gap polymer donors and fused-ring electron acceptors. [5][6][7] Regarding fullerene-based and fused-ring electron acceptor-based devices,a ll-polymer solar cells (all-PSCs) composed of ac onjugated polymer donor and an n-type conjugated polymer offer unique attractions due to their special advantages of morphological stability and flexibility. [8][9][10][11][12][13][14][15][16] Forp ractical applications,t he morphological stability of the all-PSCs against the mechanical and thermal stresses is beneficial for applications in flexible large-scale and stable devices.Although the PCE of all-PSCs has reached 10 %, [15] the performance of all-PSCs still lag behind that of state-of-theart small-molecule-based devices,o wing to the lack of suitable n-type polymer acceptors.T od ate,t he number of polymer acceptors developed for all-PSCs are limited, and only five studies have reported all-PSCs with ap hotovoltaic efficiency over 8% for ab inary system.

Introducing Porphyrin Units by Random Copolymerization Into NDI-Based Acceptor for All Polymer Solar Cells

“…(e-h) TEM images of PBDB-T:PNDI-P(x) (2:1 w:w) and PBDB-T:N2200 (2:1 w:w) blended films on the actual optimum devices. PBDB-T:N2200 solar cell exhibits a PCE of 5.27% with a V OC of 0.82 V, a J SC of 11.87 mA/cm 2 , and a FF of 54.16%, which is well-consistent with the devices we reported previously (Chen et al, 2018). The PBDB-T:PNDI-P5 solar cell presents overall improved device parameters in comparison to PBDB-T:N2200 cells, including a superior PCE of 5.86%, a higher J SC of 12.21 mA/cm 2 , a higher V OC of 0.86, and a higher FF of 55.99%.…”

“…regulate the photovoltaic performance of polymer acceptors through random copolymerization (Li et al, 2016;Chen et al, 2018;Liu et al, 2018;Xu et al, 2018;Kolhe et al, 2019). For most random copolymer-based systems, the morphology of the active layer can be fine-tuned through regulation of the crystallinity of the random copolymers.…”

“…Apart from optimizing the morphology of the bulkheterojunction, the strong and broadened light absorption of polymer acceptor is also critical to optimize the performance of all-PSCs. Recently, our group introduced the dye group, 2-(1, 1 ′ -dicyanomethylene)-4-(3-thienylmethylene) rhodanine (TR), into the NDI-based acceptor, obtaining improved extinction coefficient, raised the lowest unoccupied molecular orbital (LUMO) energy levels, and reduced crystallization (Chen et al, 2018). Inspired by this strategy, we are interested in introducing other chromophores into terpolymers to improve the absorption of polymers.…”

Ternary All-Polymer Solar Cells With 8.5% Power Conversion Efficiency and Excellent Thermal Stability

“…Thus, all-polymer solar cells (all-PSCs) consisting of a polymeric donor and acceptor have attracted more and more attention and are promising for use in realizing highly efficient and stable solar cells (Kim et al, 2015;Kang et al, 2016;Liu et al, 2016Liu et al, , 2018bLong et al, 2016;Wang et al, 2017;Zhang et al, 2017). Encouragingly, all-PSCs have recently achieved over 10% PCEs (Fan et al, 2017a(Fan et al, ,b, 2018(Fan et al, , 2019bLi et al, 2017a;Zhang et al, 2017;Chen et al, 2018;Kolhe et al, 2019;Li Z. et al, 2019;Meng et al, 2019;Yao et al, 2019;Zhu et al, 2019;Zhao et al, 2020). To date, highly efficient all-PSCs are mostly based on naphthalene diimide (NDI) polymer acceptors, because of their high electron mobility, suitable energy levels, and tunable BHJ morphology Li et al, 2016;Fan et al, 2017a,b;Liu et al, 2018b).…”

Imide‐Functionalized Polymer Semiconductors

“…Moreover,t he 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 m h,SCLC /m e,SCLC value, afforded ah igh PCE of 8.13 %. [72]…”