Surpassing 13% Efficiency for Polythiophene Organic Solar Cells Processed from Nonhalogenated Solvent

Abstract

Benefiting from low cost and simple synthesis, polythiophene (PT) derivatives are one of the most popular donor materials for organic solar cells (OSCs). However, polythiophene‐based OSCs still suffer from inferior power conversion efficiency (PCE) than those based on donor–acceptor (D–A)‐type conjugated polymers. Herein, a fluorinated polythiophene derivative, namely P4T2F‐HD, is introduced to modulate the miscibility and morphology of the bulk heterojunction (BHJ)‐active layer, leading to a significant improvement of the OSC performance. The Flory–Huggins interaction parameters calculated from the surface energy and differential scanning calorimetry results suggest that P4T2F‐HD shows moderate miscibility with the popular nonfullerene acceptor Y6‐BO (2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐butyloctyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2′,3′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile), while poly(3‐hexylthiophene) (P3HT) is very miscible with Y6‐BO. As a result, the P4T2F‐HD case forms desired nanoscale phase separation in the BHJ film while the P3HT case forms a completely mixed BHJ film, as revealed by transmission electron microscopy (TEM) and grazing‐incidence wide‐angle X‐ray scattering (GIWAXS). By optimizing the cathode interface and the morphology of the P4T2F‐HD:Y6‐BO films processed from nonhalogenated solvents, a new record PCE of 13.65% for polythiophene‐based OSCs is demonstrated. This work highlights the importance of controlling D/A interactions for achieving desired morphology and also demonstrates a promising OSC system for potential cost‐effective organic photovoltaics.

Polymerizing small molecular acceptors for efficient all‐polymer solar cells

“…Alternatively, more attention should be paid to developing novel and low-cost polymer donors with the desired characteristics for next generation all-PSCs, such as cost-effective poly(thienylenevinylene) donor. 51,52 It has been recognized that the most efficient PSMAs suffer from similar issues, which are mainly determined by the SMAs. As an alternative candidate to alleviate these issues, highly efficient unfused small molecular acceptors (UF-SMAs) have recently attracted broad interest.…”

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

“…Thus, developing easily accessible and cost-effective photovoltaic polymers is highly desired. As a variety of the latest studies have firmly highlighted the great potential of polythiophene and its derivatives [94][95][96][97][98][99][100][101][102] in solar cells, applying various polythiophenes and their derivatives might be possible to provide new paths to balance efficiency and cost of all-PSCs.…”

Recent progress in organic solar cells based on non-fullerene acceptors: materials to devices

“…This donor yielded the highest PCE of 13.34% when combined with the Y6-BO acceptor in nonhalogenated solvent. 25…”