Integrated manufacturing of REciclable multi-material COmposites for the TRANSport sector

MPhS?C2 with shortened terminal alkyl chain, features thermal annealing (TA)?insensitive aggregation and condense packing, leading to suppressed upshifts of highest occupied molecular orbital energy level during TA, and efficient charge transport at small phase separation in BTP?eC9 blended devices, obtaining the highest PCE of 17.11% with ?Vnr of 0.192 V in ASM?OSCs.A critical bottleneck for further efficiency breakthroughs in organic solar cells (OSCs) is to minimize the non?radiative energy loss (e?Vnr) while maximizing the charge generation. With the development of highly emissive low?bandgap non?fullerene acceptors, the design of high?performance donors becomes critical to enable the blend with the electroluminescence quantum efficiency to approach or surpass the pristine acceptor. Herein, by shortening the end?capped alkyl chains of the small?molecular donors from hexyl (MPhS?C6) to ethyl (MPhS?C2), the material obtained aggregation that was insensitive to thermal annealing (TA) along with condensed packing simultaneously. The former leads to small phase separation and suppressed upshifts of the highest occupied molecular orbital energy level during TA, and the latter facilitates its efficient charge?transport at aggregation?less packing. Hence, the ?Vnr decreases from 0.242 to 0.182 V, from MPhS?C6 to MPhS?C2 based OSCs. An excellent PCE of 17.11% is obtained by 1,8?diiodoctane addition due to almost unchanged high Jsc (26.6 mA cm?2) and Voc (0.888 V) with improved fill factor, which is the record efficiency with the smallest energy loss (0.497 eV) and ?Vnr (0.192 V) in all?small?molecule OSCs. These results emphasize the potential material design direction of obtaining concurrent TA?insensitive aggregation and condensed packing to maximize the device performances with a super low ?Vnr.

» Publication Date: 03/11/2022

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