“Double-Acceptor-Type” Random Conjugated Terpolymer Donors for Additive-Free Non-Fullerene Organic Solar Cells

Abstract

Random conjugated terpolymers (RCTs) not only promote great comprehension and realization for the state-of-the-art highly effective non-fullerene organic solar cells (OSCs) but also offer a simple and practical synthetic strategy. However, the photovoltaic properties of RCTs yet lagged behind that of the donor−acceptor (D−A) alternating copolymer, especially in additivefree devices. Hence, we developed two feasible "double-acceptor-type" random conjugated terpolymers, PBDB-TAZ20 and PBDB-TAZ40. The additive-free OSCs based on PBDB-TAZ20:ITIC and PBDB-TAZ40:ITIC exhibit decent efficiencies of 12.34 and 11.27%, respectively, which both surpass the PBDB-T:ITIC-based device. For RCTs, the reasonably weakened crystallinity and the reduced phase separation degree are demonstrated to help in improving charge transport, reducing bimolecular recombination, and thus enhancing the photovoltaic performance of additive-free OSCs. The results imply that adding a third moiety into the D−A polymer donors provides a simple but efficient synthetic approach for high-performance OSCs.

High performance conjugated terpolymers as electron donors in nonfullerene organic solar cells

“…[19][20][21][22][23][24] For better fine-tuning of the E HOMO and E LUMO levels, and, as a consequence, the bandgap of the donor materials, a nonconventional molecular design strategy, beyond the classical D-A approach, for new p-conjugated polymers with high photovoltaic performance is being explored in the field; however, very limited studies have been presented up to now. [25][26][27][28][29][30][31][32] Taking this into account, a facile D 1 -D 2 -D 1 -A p-conjugated polymer backbone is presented in this work by the addition of another multi-fused ladder-type arene as a building block between the D and A moieties in a regular alternation and not in a random approach. The beneficial role of the more extended structures, especially those containing more than one electron donating unit connected to each other, hence increasing the D-A distance, has been highlighted.…”

Control of aggregated structure of photovoltaic polymers for high‐efficiency solar cells

“…Modification of polymer backbone by copolymerizing disparate units can combine the features of copolymeric units to modulate the aggregation properties. [326][327][328] Copolymer ES1 was synthesized by introducing fluorine and ester substituted thiophene unit (FE-T). [327] Compared to PBDB-TF, the introduction of FE-T enhanced face-on π-π stacking through S⋅⋅⋅O and S⋅⋅⋅F interaction and therefore resulted in fibril nanostructure of ES1:Y6 film.…”

“…The ES1:Y6-based PSCs with optimized morphology reached a considerable PCE of 16.4%. Chen et al [328] introduced benzotriazole unit into PBDB-T, forming PBDB-TAZ20 and PBDB-TAZ40. PBDB-TAZ20 exhibited improved miscibility with ITIC and the blend film exhibited weaker phase separation than PBDB-T:ITIC.…”

Performance and Stability of Polymer : Nonfullerene Solar Cells with 100 °C‐Annealed Electron‐Collecting Combination Layers

“…[4][5][6][7][8] In recent years, the fullerene derivatives as electron acceptor have been replaced by nonfullerene materials with extended light absorption characteristics. [9][10][11][12][13][14][15] Such brand-new polymer : nonfullerene solar cells showed PCEs around 18 % due to the extended light absorption toward near infrared (NIR) range and improved charge transport characteristics of nonfullerene acceptors. [16][17][18] Most high-efficiency polymer : nonfullerene solar cells so far have been fabricated with an inverted-type device structure and further improvement was achieved by employing interlayers (interfacial layers) on metal oxide-based electron-collecting buffer layers (ECBLs).…”