>10% Efficiency Polymer:Fullerene Solar Cells with Polyacetylene‐Based Polyelectrolyte Interlayers

Abstract

Polymer solar cells have gained great attention due to their tremendous potential for applications in light-weight, large-area, and flexible photovoltaic modules fabricated via continuous roll-to-roll processes. Despite the significant progress, however, their efficiency and operating stability are still inadequate for commercial applications. Interfacial engineering of the electron-collecting buffer layer and the organic photoactive layer through the use of organic dipole interlayers, has been proposed as a simple and scalable way to improve the overall solar cell performance. Here, highly efficient inverted polymer:fullerene solar cells have been successfully developed with a power conversion efficiency of over 10%. The bulk heterojunction layer consists of the poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b]dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] (PTB7-Th) and the [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 71 BM), as the electron donor and electron acceptor, respectively. Key to this success is the insertion of the ionic polyacetylene-based conjugated polymer, poly(N-dodecyl-2-ethynylpyridinium bromide), as an interfacial dipole layer. The latter is shown to lower the work function of the electron transporting zinc oxide layer and increase the built-in potential, consequently facilitating efficient charge transport/extraction. Optimized solar cells exhibit power conversion efficiency values exceeding 10% while their operating stability under continuous solar-simulated illumination is significantly enhanced when ultraviolet light is effectively blocked using a suitable optical filter.

Synthesis of Sulfur/Nitrogen‐Enriched Polyimide and Interlayer Application for Inverted Polymer:Nonfullerene Solar Cells

“…Finally, the stability of devices was examined to understand whether it is affected by the E‐PI interlayers. As shown in Figure a,b, the J – V curves of devices became gradually poor with time irrespective of the presence of the E‐PI interlayers due to the intrinsic degradation of the BHJ layers as reported in the previous works . However, it is noted that the decay rate in the J – V curves was relatively slower for the devices with the E‐PI interlayers than the control devices.…”

High‐Efficiency Polymer:Nonfullerene Solar Cells with Quaterthiophene‐Containing Polyimide Interlayers

“…Taking into account the ultrathin states at a scale of several nanometers or less, the insulating polymers for interlayers should be thermally and physicochemically stable for the long‐term durability of organic solar cells. However, conventional insulating polymers used for interlayers have low thermal stability, for example, as noted from their glass transition temperature ( T g ), of T g = −28.15 °C for polyethyleneimine (PEI), T g = −24 °C for polyethyleneimine‐ethoxylated (PEIE), and T g = 54 °C for poly(2‐ethyl‐2‐oxazoline) (PEOz) . Therefore, it is strongly required to develop highly stable polymers for the insulating polymer interlayers toward durable organic solar cells.…”

Performance and Stability of Polymer : Nonfullerene Solar Cells with 100 °C‐Annealed Electron‐Collecting Combination Layers

“…Basically, the fast decay of solar cell performances can be ascribed to the degradation in the BHJ (PBDB-T : IT-M) layers as reported in the previous works. [47][48][49] Nevertheless, the slower decay for the 6 wt % solar cells than the 0 wt % solar cells can be attributed to the benefit of hybrid combination layers (ZnO : PEOz/PEOz) with the fine texture structures that could improve adhesion between the BHJ and combination layers (see AFM images in Figure 3).…”