End‐Group Engineering of Chlorine‐Trialkylsiylthienyl Chain‐Substituted Small‐Molecule Donors for High‐Efficiency Ternary Solar Cells

Abstract

Ternary architecture has been widely demonstrated as a facile and efficient strategy to boost the performance of organic solar cells (OSCs). However, the rational design of the third component with suitable core and end‐group modification is still a challenge. Herein, two new small‐molecule (SM) donors BT‐CN and BT‐ER, featuring the identical conjugated backbone with distinct end group, have been designed, synthesized, and introduced into the PM6:Y6 binary system as the second donor. Both molecules exhibit complementary absorption and good miscibility with PM6, contributing to the nanofibrous phases and strong face‐on molecular packing. Importantly, the incorporation of BT‐CN/BT‐ER has significantly facilitated charge collection and transportation with remarkable suppression of carrier recombination. As a result, ternary OSCs with 20 wt% BT‐CN/BT‐ER achieved a PCE of 16.8%/17.22% with synchronously increased open‐circuit voltage (VOC), short‐circuit current density (JSC) and fill factor (FF). Moreover, replacing Y6 with L8‐BO further improves the PCE to 18.05%/18.11%, indicating the universality of both molecules as the third component. This work demonstrates not only two efficient SM donors with 4,8‐bis(4‐chloro‐5‐(tripropylsilyl)thiophen‐2‐yl) benzo[1,2‐b:4,5‐b′]dithiophene (BDTT‐SiCl) as the core but also end group modification strategy to fine‐tune the absorption spectrum, molecular packing, and energy levels of SM donors to construct high‐performance ternary OSCs.

Synergetic alkoxy side-chain and chlorine-contained end group strategy toward high performance ultra-narrow bandgap small molecule acceptors

“…In the heating process, BZ4F-O-1 and BZO-4Cl exhibit their endothermic peaks at 240.4 o C and 215.9 o C, respectively. The BZ4F-O-1: BZO-4Cl (1: 1, w/w) mixture shows a medium value of melting temperature at 223.4 o C, while the melting peaks of neat BZ4F-O-1 and BZO-4Cl are disappeared, suggesting good miscibility between BZ4F-O-1 and BZO-4Cl [51] . Atomic force microscopy (AFM) is employed to investigate the surface morphology of the devices based on PBDB-T: BZ4F-O-1, PBDB-T: BZO-4Cl and PBDB-T: BZ4F-O-1: BZO-4Cl blends.…”

Dopant‐Free Two‐Dimensional Hole Transport Small Molecules Enable Efficient Perovskite Solar Cells

“…[25,26] Moreover, 2D conjugated molecules are more inclined to form a face-on stacking orientation, enabling efficient hole extraction and transport in solar cells. [27][28][29] However, the 2D conjugate engineering strategy is largely unexplored in D-A structure small molecule HTMs. [30,31] Herein, for the first time, triphenylamine (TPA) groups were incorporated as side chains of BDT unit to extend the longitudinal conjugate, achieving two 2D small molecule HTMs (XF2 and XF3) with longitudinal conjugate extension (Figure 1).…”

“…[ 25,26 ] Moreover, 2D conjugated molecules are more inclined to form a face‐on stacking orientation, enabling efficient hole extraction and transport in solar cells. [ 27–29 ] However, the 2D conjugate engineering strategy is largely unexplored in D–A structure small molecule HTMs. [ 30,31 ]…”

18.9% Efficiency Ternary Organic Solar Cells Enabled by Isomerization Engineering of Chlorine‐Substitution on Small Molecule Donors

“…[46] In our previous study, we reported different end-group-based SM donors and the resulting ternary OSCs reached a PCE of 18.11%. [47] Besides, we modified the BDT unit by introducing a phenyl-substituted side chain, to regulate the energy level and crystallinity of the material. The ternary OSCs achieved PCE of 18.41%.…”