A Self‐Organized Poly(vinylpyrrolidone)‐Based Cathode Interlayer in Inverted Fullerene‐Free Organic Solar Cells

Abstract

surface of the film, forming the interlayer and active layer simultaneously. In order to better distinguish, the two approaches are recognized as the step-by-step preparation method and the self-organization method, respectively, in this work. The self-organization method not only simplifies the fabrication procedure significantly but also makes the tolerance of the interlayer to thickness variation no need consideration. And hence, intensive investigations have been focused on the self-organization method in fullerene-based OSCs. [4][5][6][7][8][9][10][11][12] The self-organization method is based on the self-assembly of the interlayer material during the film deposition process, and many factors have been suggested to explain the origin of the migration of the interlayer materials. It has been demonstrated that when an interlayer material has higher surface energy and stronger interaction with the indium tin oxide (ITO) electrode, it may tend to migrate to the near ITO side, and vice versa. [12][13][14][15][16] For instance, Wei et al. introduced fluorocarbon chains to [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) to decrease the surface energy of PC 61 BM, and as a result, the fluorinated PC 61 BM segregated to the top of the AL, forming the CIL and AL simultaneously. [15] By contrast, when PC 61 BM was substituted with high-surfaceenergy moieties, such as amino groups, the modified PC 61 BM could migrate to the interface between the AL and the ITO substrate. [5] Interestingly, poly(ethylene glycol) (PEG) and its derivatives, materials with high surface energies, have been demonstrated to prefer to self-organize at the top of the AL because of the strong interaction between the PEG segment and the top metal electrode. [12,[16][17][18][19][20] Poly(vinylpyrrolidone) (PVP), poly(2-vinylpyridine) (P2VP), poly [(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN), polyethyleneimine (PEI), oleamide, and fluorinated zinc oxide have also been used to self-organize CILs in OSCs. [9,13,[21][22][23][24] All the aforementioned materials were applied in fullerene-based OSCs via the self-organization method, and the reported utilization of PVP through self-organization method is associated with a conventional device architecture, [21] which makes its application in the inverted devices seem impossible. Meanwhile, for fullerene-free OSCs, that have more potential for realizing higher photovoltaic performances and in future practical applications, no example has been developed to date.In this work, we demonstrate the first example that uses PVP as the CIL in the inverted OSCs via the self-organization method.Herein, poly(vinylpyrrolidone) (PVP) is used as the cathode interlayer (CIL) through the self-organization method in inverted organic solar cells (OSCs). By coating a solution of PVP and active layer materials onto a glass/indium tin oxide (ITO) substrate, the PVP can segregate to the near ITO side due to its high surface energy and strong intermolecular interaction with the I...

One‐Step Blade‐Coated Highly Efficient Nonfullerene Organic Solar Cells with a Self‐Assembled Interfacial Layer Enabled by Solvent Vapor Annealing

“…Moreover, the integral current density values deduced from EQE spectra match well with those obtained from the J–V measurements (Table ). The PCEs of one‐step fullerene/NF OSCs fabricated by doctor blade in previous reports are presented in Figure c . It can be seen that our one‐step doctor‐bladed OSCs with a conventional NF system show the very high PCEs among the reported results, due to the optimized electrical property of IL through SVA.…”

“…The PCE of one‐step printing type‐I device with SVA treatment is 38% higher than 8.05% of type‐I device without SVA. To the best of our knowledge, the obtained PCE value of >11% is one of the highest values reported to date for one‐step printed OSCs featuring a self‐assembled IL . For comparison, two‐step doctor‐blade printing OSC was also produced with varying PFN thickness, substrate temperature as well as SVA treatment (Figure S4–6, Table S4–6, Supporting Information).…”

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