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

Abstract

All‐polymer solar cells (all‐PSCs), with the photoactive layer exclusively composed of polymers as both donor and acceptor, have attracted growing attention due to their unique merits in optical, thermal and mechanical durability. Through the combined strategies in materials design and device engineering, recently the power conversion efficiencies of single‐junction all‐PSCs have been boosted up to 11 %. This review focuses on the recent progress of all‐PSCs comprising of wide band‐gap p‐type polymers, especially those based on the units of thieno[3,4‐c]pyrrole‐4,6(5H)‐dione], fluorinated benzotriazole, benzo[1,2‐c:4,5‐c′]dithiophene‐4,8‐dione, and pyrrolo[3,4‐f]benzotriazole‐5,7(6H)‐dione. Meantime, several categories of n‐type polymers used to match with these polymer donors are also reviewed. Finally, a brief summary of the strategies of molecular design and morphology optimization is given, and strategies toward further improving performance of all‐PSCs are outlined.

High‐Performance All‐Polymer Solar Cells Enabled by n‐Type Polymers with an Ultranarrow Bandgap Down to 1.28 eV

“…[31][32][33] For instance, blending the NDI-based polymer N2200 [34,35] with tailored-made polymer donors yielded a series of all-PSCs with record efficiencies. [36][37][38][39] Although the most successful device performance in all-PSCs is achieved from NDI-and PDI-based copolymers, these polymers usually show relatively large bandgap and low absorption coefficient in long-wavelength region due to their twisted backbones and intrinsic electronic structures, thus severely restricting the short-circuit current (J sc ) and hence PCE in all-PSCs. [28,35,39] Such absorption character also severely limits the device performance of polymer acceptors based on B←N embedded electron-deficient building blocks.…”

“…[36][37][38][39] Although the most successful device performance in all-PSCs is achieved from NDI-and PDI-based copolymers, these polymers usually show relatively large bandgap and low absorption coefficient in long-wavelength region due to their twisted backbones and intrinsic electronic structures, thus severely restricting the short-circuit current (J sc ) and hence PCE in all-PSCs. [28,35,39] Such absorption character also severely limits the device performance of polymer acceptors based on B←N embedded electron-deficient building blocks. [24,26,40] Figure 1 displays the representative polymer acceptors that exhibit high J sc and PCE in all-PSCs with their optical bandgap (E g opt ) also included.…”

Eco‐friendly solution processing of all‐polymer solar cells: Recent advances and future perspective

“…[16][17][18][19] Compared with polymer:small molecule solar cells, all-PSCs often exhibit morphological stability and mechanical robustness properties, which are favorable to manufacture large-scale solar cell modules. [20][21][22][23] The underlining mechanism for morphological stability of all-PSCs is the entanglement of two polymer species upon mixing, and thus much slow diffusion kinetics. 24,25 Besides, the advantages of all-PSCs include high donor:acceptor blend ratio tolerance to photovoltaic performance, excellent film-forming properties owing to the higher viscosity of polymers in solution, and easily tunable light absorption, energy level and blend morphology.…”

A pyrrolopyridazinedione-based copolymer for fullerene-free organic solar cells

“…[11][12][13][14][15][16] Notably, the most efficient polymer:fullerene based devices emerged from polymers with 2D-conjugated benzodithiophene (BDT) as comonomer, 17,18 a structural motif present in several highly efficient wide bandgap p-type polymers. 10,[19][20][21][22] In a very recent approach using NFAs, a PCE of 13% could be obtained with a tetrazine containing conjugated polymer (PSFTZ, 4,8bis(5-((2-butyloctyl)thio)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b 0 ] dithiophene-alt-3,6-bis(4-octylthiophen-2-yl)-1,2,4,5-tetrazine) in combination with the NFA Y6. 7 This already high performance could be even further pushed by adding Pt(Ph) 2 (DMSO) 2 to reach 16.35%, which was claimed to be due to morphology improvements.…”