Novel Oligomer Enables Green Solvent Processed 17.5% Ternary Organic Solar Cells: Synergistic Energy Loss Reduction and Morphology Fine‐Tuning

Abstract

The large non‐radiative recombination is the main factor that limits state‐of‐the‐art organic solar cells (OSCs). In this work, two novel structurally similar oligomers (named 5BDTBDD and 5BDDBDT) with D‐A‐D‐A‐D and A‐D‐A‐D‐A configuration are synthesized for high‐performance ternary OSCs with low energy loss. As third components, these PM6 analogue oligomers effectively suppress the non‐radiative recombination in OSCs. Although the highest occupied molecular orbital (HOMO) levels of 5BDTBDD and 5BDDBDT are higher than that of PM6, the oligomers enabled ultra‐high electroluminescence quantum efficiency (EQEEL) of 0.05% and improved VOC, indicating suppressing non‐radiative recombination overweighs the common belief of deeper HOMO requirement in third component selection. Moreover, the different compatibility of 5BDTBDD and 5BDDBDT with PM6 and BTP‐BO4Cl fine‐tunes the active layer morphology with synergistic effects. The ternary devices based on PM6:5BDTBDD:BTPBO4Cl and PM6:5BDDBDT:BTP‐BO4Cl achieve a significantly improved PCEs of 17.54% and 17.32%, representing the state‐of‐the art OSCs processed by green solvent of o‐xylene. The strategy using novel oligomer as third component also has very wide composition tolerance in ternary OSCs. This is the first work that demonstrates novel structurally compatible D‐A type oligomers are effective third components, and provides new understanding of synergetic energy loss mechanisms towards high performance OSCs.

Role of Neutrophil Lymphocyte Ratio (NLR) in Predicting Disease Severity in Covid -19

“…Different studies suggest NLR should be monitored starting from the first day of hospitalization to predict disease progression from mild to severe. [18][19][20]…”

An acceptor with an asymmetric and extended conjugated backbone for high-efficiency organic solar cells with low nonradiative energy loss

“…59–64 With the structural modifications, the molecular absorptions, energy levels and packing modes can be finely tuned, and corresponding devices with improved efficiencies over 19% have been achieved. 14–20 However, to the best of our knowledge, E loss values for the vast majority of the reported devices of Y6 derivatives are still higher than 0.5 eV, 31,49,65–69 as they mainly suffer from the large nonradiative energy loss over 0.2 eV. 49,65,66,69 Thus, it is still a challenging work to minimize the nonradiative loss via careful molecular design.…”

Optimizing sequence structures by stepwise-feeding terpolymerization for high-performance organic solar cells

“…Hou et al incorporated an ester-substituted thiophene unit into the PM6 backbone to offer simultaneously enhanced J sc and V oc in OSCs. 7 Although remarkable achievements have been made in random terpolymerization, i.e., modulating the chemical structure and molar ratio of the third component, [8][9][10] which are processed in one-pot polymerization, the one-pot polymerization method wherein all the monomers are added in at once is accompanied by the following inevitable problems: (i) the D-A periodic sequence distribution in the polymer will be seriously interrupted when inserting the third component; (ii) the position of the third component in the backbone is unclear; (iii) the obtained structure suffers from serious batch-to-batch variation due to the random copolymerization mechanism and different monomer reactivities. Therefore, it is necessary to investigate the inuence of polymerization methods on the polymer structure and corresponding device performances.…”