Random nitroxide radical conjugated polymer additives enable 19.32 % efficiency of organic solar cells

Journal article, 2025

Minimizing non-radiative energy losses (Enon-radLoss) has been crucial to further boosting the efficiency of non-fullerene organic solar cells (NFAs-OSCs) to a new performance regime. Recently, we have developed an alternating radical conjugated polymer named GDTA from 3,4-dioctylthiophene flanked benzo[1,2-b;4,5-b’]dithiophene (BDT) and 1,4-bis(4-oxy-2,2,6,6-tetramethylpiperidine-1-oxyl)phthalate (BTMP), and demonstrated that GDTA can be used as additives to improve the performance of OSCs from a broad of photovoltaic materials system. Herein, the GDTA is accordingly optimized by varying the molar feed ratios of monomers containing BTMP and BDT moieties from 9:11, 2:3, 3:7 and 1:4, to generate the random radical conjugated polymers (R-RCPs) of R-GDTA90, R-GDTA80, R-GDTA60, R-GDTA40. For the NFAs-OSCs from PM6:Y6 blends, the addition of all the R-RCPs additives results in the general improvement of the efficiency of 9.3–11.5 % (16.12 % to 17.62 % ∼ 17.98 %). On contrary, the efficiencies of the devices from D18-Cl: L8-BO blends are firstly increased to 19.32 %, 19.02 % and finally dropped to 17.29 %, as the R-GDTA90, R-GDTA80, R-GDTA60 and R-GDTA40 are separately used as additives. The particularly interesting NFAs-OSCs, which present higher efficiency of 17.98 % and 19.32 % than those of 17.62 % and 18.78 % for devices with the counterpart GDTA additives, were achieved from PM6: Y6 and D18-Cl: L8-BO with the 2.0 wt% of R-GDTA80 and R-GDTA90 additives, respectively. Besides that, the more efficiently suppressed charge recombination and energy loss of the devices with the best-fitting R-RCPs in contrast to NFAs-OSCs with GDTA additives, were observed and supported by a range of physical measurements.