Designing Simple Conjugated Polymers for Scalable and Efficient Organic Solar Cells

Abstract

Conjugated polymers have a long history of exploration and use in organic solar cells, and over the last twenty-five years, marked increases in the solar cell efficiency have been achieved. However, the synthetic complexity of these materials has also drastically increased, which makes the scalability of the highestefficiency materials difficult. If conjugated polymers could be designed to exhibit both high efficiency and straightforward synthesis, the road to commercial reality would be more achievable. For that reason, a new synthetic approach was designed towards PTQ10 (= poly[(thiophene)-alt-(6,7-difluoro-2-(2-hexyldecyloxy)quinoxaline)]). The new synthetic approach to make PTQ10 brought a significant reduction in cost (1/7th the original) and could also easily accommodate different side chains to move towards green processing solvents. Furthermore, high-efficiency organic solar cells were demonstrated with a PTQ10:Y6 blend exhibiting approximately 15 % efficiency.

Simple Synthesis of Conjugated Polymers Enabled via Pyrrolo[3,2-b]pyrroles

“…68,69 The synthetic complexity of PTQ10 (entry 2, Table 1) is also calculated to be synthetically simple due to the minimization of preparatory steps. Notably, when calculating the synthetic complexity of the proposed cost-effective route for PTQ10 reported by You and co-workers (entry 3, Table 1), 12 the addition of synthetic steps leads to nearly doubling of the synthetic complexity compared to the original synthetic strategy and results in a copolymer more synthetically complex than our DHPP-co-ProDOT. While both PTQ10 approaches still represent simple synthetic strategies for conjugated polymers, Stille cross-coupling polymerizations are used in both studies, which may be detrimental to scalability efforts due to the generation of stoichiometric amounts of toxic waste.…”

“…Additionally, You and co-workers performed a cost analysis of PTQ10 and suggested that current synthetic approaches are cost-prohibitive. These drawbacks limited the scalability and commercial manufacturing of this polymer and motivated the pursuit of alternative synthetic approaches that ultimately reduced the price per gram to ∼1/7th the original cost . Additional approaches for accessing structurally simpler conjugated copolymers involve using commercially available monomers such as bithiophene or ester- and alkyl-functionalized monomers that require fewer synthetic steps. − Recently, Marks and co-workers also reported a simpler synthesis of naphthalene diimide and isoindigo copolymers that were utilized in all-polymer solar cell devices .…”

B ← N Coordination Enables Efficient p-Doping in a Pyrazine-Based Polymer Donor Toward Enhanced Photovoltaic Performance

“…150−200 $/g. 40 Compared to the benzodithiophene (BDT)based high-performance polymer donors, PBP-Cl is constructed using 2,5-dibromopyrazine, which is economical and widely accessible (Table S2). Gel permeation chromatography (GPC) tests reveal a high number-averaged molecular weight (M n ) of 113 kDa and a low polydispersity of 2.0 (Figure S1).…”

“…21 $/g (Table S1), sharply lower than other well-known high-performance polymer donors, e.g ., PTB7, PM6, and D18, whose costs are ca . 150–200 $/g . Compared to the benzodithiophene (BDT)-based high-performance polymer donors, PBP-Cl is constructed using 2,5-dibromopyrazine, which is economical and widely accessible (Table S2).…”

Polymers in High-Efficiency Solar Cells: The Latest Reports

“…They acquired the PCE of 15%. In [ 138 ], Caliskan et al synthesized a donor material based on benzo dithiophene by attaching a 2-(2-octyldodecyl)selenophene ring at the fourth and eighth position of benzene ring in BDT. The structure of the solar cell was ITO/PEDOT:PSS/Polymer:PC 71 BM/LiF/Al and the obtained PCEs were 2.36%, 2.07% and 2.45% for P1, P2 and P3, respectively [ 139 ].…”