Poly(sulfobetaine methacrylate)s as Electrode Modifiers for Inverted Organic Electronics

Abstract

We demonstrate the use of poly(sulfobetaine methacrylate) (PSBMA), and its pyrene-containing copolymer, as solution-processable work function reducers for inverted organic electronic devices. A notable feature of PSBMA is its orthogonal solubility relative to solvents typically employed in the processing of organic semiconductors. A strong permanent dipole moment on the sulfobetaine moiety was calculated by density functional theory. PSBMA interlayers reduced the work function of metals, graphene, and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) by over 1 eV, and an ultrathin interlayer of PSBMA reduced the electron injection barrier between indium tin oxide (ITO) and C70 by 0.67 eV. As a result, the performance of organic photovoltaic devices with PSBMA interlayers is significantly improved, and enhanced electron injection is demonstrated in electron-only devices with ITO, PEDOT:PSS, and graphene electrodes. This work makes available a new class of dipole-rich, counterion-free, pH insensitive polymer interlayers with demonstrated effectiveness in inverted devices.

Zwitterions for Organic/Perovskite Solar Cells, Light‐Emitting Devices, and Lithium Ion Batteries: Recent Progress and Perspectives

“…[149] Four ZEIs were synthesized with the backbones of all-thiophene (PTSB-1 and PTSB-2) to thiophene-alt-benzothiadiazole (PTBTSB-1 or PTBTSB-2) (Scheme 3), having methylene and butylene units disintegrating the zwitterions from the main backbone. [150] Inverted devices were constructed containing two small molecular layers with the architecture of Al(100 nm)/molybdenum-trioxide(MoO 3 )(10 nm) /5,10,15,20-tetraphenylbenzo [5,6]indeno[1,2,3-cd]benzo [5,6] indeno[1,2,3-lm]perylene(DBP)(15 nm)/C 70 (40 nm)/PSBMA (0-16 nm)/ITO. [149] Owing to the ability of sulfobetaine zwitterions to lower the WF of electrode, poly(sulfobetaine methacrylate) (PSBMA) (Scheme 3) was used as interlayer to fabricate the solution processable inverted PSC devices.…”

“…By employing these ZEIs between the Al/Ag electrode and active layer, PSCs based on PTB7: PC 71 BM realized a remarkable increase in the PCE of >500%, (from 0.92% to 5.78%) for Ag electrode devices, and 68% (from 4.39% to 7.36%) for Al electrode devices ( Table 2). [150] This is due to the large electron injection barrier of 0.76 eV. [150] Inverted devices were constructed containing two small molecular layers with the architecture of Al(100 nm)/molybdenum-trioxide(MoO 3 )(10 nm) /5,10,15,20-tetraphenylbenzo [5,6]indeno[1,2,3-cd]benzo [5,6] indeno[1,2,3-lm]perylene(DBP)(15 nm)/C 70 (40 nm)/PSBMA (0-16 nm)/ITO.…”

“…[149] Owing to the ability of sulfobetaine zwitterions to lower the WF of electrode, poly(sulfobetaine methacrylate) (PSBMA) (Scheme 3) was used as interlayer to fabricate the solution processable inverted PSC devices. [150] Zwitterions have the ability to induce a net molecular dipole with the metal electrode. The devices without PSBMA interlayer exhibited poor performance with a V OC of 0.60 V, an FF of 0.38, a J SC of 3.14 mA cm −2 , and a PCE of 0.71%.…”

Switchable Materials Containing Polyzwitterion Moieties

“…Thermo-responsive poly(38) polymers have recently been successfully used as ion-permeable membranes in energy storage devices; differences in the specific storage capacity of the electrode for Li ion when heated from 20 to 80˝C showed a reversibly decrease by >50%, compared to a 30% increase without polymer modification [122]. The orthogonal solubility of some polyzwitterions to solvents could typically be used in the processing of organic semiconductors [123,124] and possibly of UCST, representing an open avenue for thermo-responsive and tunable platforms in organic electronic devices [122]. The external trigger as a mechanical force via ultrasonic stimuli as a component of a spatial and time-controlled switchable process represents a highly feasible approach, which was not previously reported [125,126].…”

Efficient Enhancement of Electron Transport and Collection Capability in PTB7:PC71BM‐based Solar Cells Enabled by Sulforhodamine Cathode Interlayers

“…Thus, finding solution‐processed organic interlayer has become an important issue in the field of organic solar cells. Sulforhodamine materials show an attractive potential for CILs because of their environmental‐friendliness, good water/alcohol solubility and relatively low cost, making it well suited for large area solution processing in the future. Nevertheless, the study of CILs using sulforhodamine was still limited …”