A Nitroxide Radical Conjugated Polymer as an Additive to Reduce Nonradiative Energy Loss in Organic Solar Cells

Abstract

Nonfullerene‐acceptor‐based organic solar cells (NFA‐OSCs) are now set off to the 20% power conversion efficiency milestone. To achieve this, minimizing all loss channels, including nonradiative photovoltage losses, seems a necessity. Nonradiative recombination, to a great extent, is known to be an inherent material property due to vibrationally induced decay of charge‐transfer (CT) states or their back electron transfer to the triplet excitons. Herein, it is shown that the use of a new conjugated nitroxide radical polymer with 2,2,6,6‐tetramethyl piperidine‐1‐oxyl side groups (GDTA) as an additive results in an improvement of the photovoltaic performance of NFA‐OSCs based on different active layer materials. Upon the addition of GDTA, the open‐circuit voltage (VOC), fill factor (FF), and short‐circuit current density (JSC) improve simultaneously. This approach is applied to several material systems including state‐of‐the‐art donor/acceptor pairs showing improvement from 15.8% to 17.6% (in the case of PM6:Y6) and from 17.5% to 18.3% (for PM6:BTP‐eC9). Then, the possible reasons behind the observed improvements are discussed. The results point toward the suppression of the CT state to triplet excitons loss channel. This work presents a facile, promising, and generic approach to further improve the performance of NFA‐OSCs.

Unraveling the origin of improved photovoltaic performance in acceptor–acceptor-structured perylene-diimide-based polymeric acceptors through partially fluorinating benzo[c][1,2,5]thiadiazole

“…S19 (ESI †). 69 We can see that after lightexposure for 72 h, the values of V OC , J SC , FF and PCE remained at 98%, 90%, 95% and 86%, respectively, of their initial values, indicating that these A-A type polymeric acceptors possess good stability.…”

Assembly of galvinoxyl doped in polymer–fullerene photovoltaic blends

“…Note in this regard that for OSCs not based on fullerene acceptors, the addition of Gx has been reported 7 to reduce the effectiveness of the OSCs, so the presence of fullerene is indeed important for Gx -doped blends.…”

“…4,6 On the other hand, for OSCs not based on fullerene acceptors, the addition of Gx has been reported to reduce the efficiency of the OSCs. 7 It is known that polymer-fullerene composites serving as active layers of OSCs consist of donor (polymer) and acceptor (fullerene) phases with characteristic domain sizes of about 10 nm. 8 The nanoscale arrangement of these phases is determined by the molecular structures of the composite components and impurities, and also depends on the preparation conditions.…”

“…4,6 On the other hand, for OSCs not based on fullerene acceptors, the addition of Gx has been reported to reduce the efficiency of the OSCs. 7…”

Redox: Organic Robust Radicals and Their Polymers for Energy Conversion/Storage Devices

“…Redox-active radical compounds have been mainly studied from an electrochemical perspective, but interesting results have been reported with solid phases (i.e., without electrolytes). 107,272,334 3.5.1. Electroconductive Properties.…”