A Synergistic Strategy of Manipulating the Number of Selenophene Units and Dissymmetric Central Core of Small Molecular Acceptors Enables Polymer Solar Cells with 17.5 % Efficiency

Abstract

A dissymmetric backbone and selenophene substitution on the central core was used for the synthesis of symmetric or dissymmetric A‐DA′D‐A type non‐fullerene small molecular acceptors (NF‐SMAs) with different numbers of selenophene. From S‐YSS‐Cl to A‐WSSe‐Cl and to S‐WSeSe‐Cl, a gradually red‐shifted absorption and a gradually larger electron mobility and crystallinity in neat thin film was observed. A‐WSSe‐Cl and S‐WSeSe‐Cl exhibit stronger and tighter intermolecular π–π stacking interactions, extra S⋅⋅⋅N non‐covalent intermolecular interactions from central benzothiadiazole, better ordered 3D interpenetrating charge‐transfer networks in comparison with thiophene‐based S‐YSS‐Cl. The dissymmetric A‐WSSe‐Cl‐based device has a PCE of 17.51 %, which is the highest value for selenophene‐based NF‐SMAs in binary polymer solar cells. The combination of dissymmetric core and precise replacement of selenophene on the central core is effective to improve Jsc and FF without sacrificing Voc.

NIR-Absorbing Electron Acceptor Based on a Selenium-Heterocyclic Core Attaching to Phenylalkyl Side Chains for Polymer Solar Cells with 17.3% Efficiency

“…In addition, annealing treatment can improve the domain purities of D18:BTSe-IC2F-and D18:BTSe-IC2Cl-based active layers, which is responsible for the enhancement of free charge migration, supporting high J sc and FF values. 31 The intermolecular packing characteristics in the blend films of D18:BTSe-IC2F and D18:BTSe-IC2Cl with and without annealing were further studied via GIWAXS measurements (Figure 5). The pristine D18:BTSe-IC2F blend film displayed an IP (100) lamellar scattering at q xy = 0.312 Å −1 (d = 20.1 Å) and a π−π stacking (010) peak at q z = 1.713 Å −1 (d = 3.67 Å) along the OOP direction.…”

“…For D18:BTSe-IC2F blend films, the well-distributed bicontinuous interpenetrating network structure accompanying suitable domain size is formed, which is in accordance with the AFM morphology results. In addition, annealing treatment can improve the domain purities of D18:BTSe-IC2F- and D18:BTSe-IC2Cl-based active layers, which is responsible for the enhancement of free charge migration, supporting high J sc and FF values …”

“…Among these skeleton-modulated strategies, a heterocyclic strategy, especially the selenium substitution strategy involving introducing more electron-rich heteroatom selenium into the central core of the molecular skeleton, was also regarded as an effective strategy to increase the electron-donating strength. Recently, selenium-heterocycle based FRAs incorporating selenium substitution in the outermost , or central , position of the central core have shown a red-shifted absorption spectrum compared to that of sulfur analogs, leading to an enhanced J sc as well as minimized sacrifice for V oc . As we know, selenium in comparison to sulfur is more polarizable and beneficial to greater orbital overlap for the large π-conjugation structure, forming narrower optical bandgaps due to the looser π-electron cloud delocalization .…”

π‐Extended End Groups Enable High‐Performance All‐Polymer Solar Cells with Near‐Infrared Absorption

“…Recently, encouraged by the rapid development of Y‐type SMAs, the reported PYT‐derivative polymer acceptors obtained via the “SMA polymerization” strategy have enabled new heights (PCE = 18%) for all‐PSCs. [ 8,21‐23 ] In addition, polymerized non‐fused ring electron acceptors using this strategy can significantly reduce the cost of the corresponding polymer acceptors, which is important for the industrialization of all‐PSCs technology. [ 24‐25 ]…”

Highly efficient organic solar cells with superior deformability enabled by diluting the small molecule acceptor content

“…[1][2][3] Plenty of strategies including molecular structure innovation and morphology optimization have been successfully applied to boost the efficiency of OSCs to around 17-19%. [4][5][6][7][8][9][10][11][12] However, these strategies typically fail to enhance the mechanical properties of the active layers. 13,14 For instance, increasing the backbone planarity, which is generally regarded as a feasible molecular design rule to improve charge transport ability along the conjugated plane to enhance the photon-to-electron conversion efficiency, always deteriorates the mechanical performance since it makes molecules less deformable.…”