Modification of a ZnO cathode by doping it with a hydroxyl-containing derivative - giving a ZnO-C60 cathode - provides a fullerene-derivative-rich surface and enhanced electron conduction. Inverted polymer solar cells with the ZnO-C60 cathode display markedly improved power conversion efficiency compared to those with a pristine ZnO cathode, especially when the active layer includes the low-bandgap polymer PTB7-Th.

We report a new route for the design of electroluminescent polymers by grafting high-efficiency phosphorescent organometallic complexes as dopants and charge transport moieties onto alky side chains of fully conjugated polymers for polymer light-emitting diodes (PLED) with single layer/single polymers. The polymer system studied involves polyfluorene (PF) as the base conjugated polymer, carbazole (Cz) as the charge transport moiety and a source for green emission by forming an electroplex with the PF main chain, and cyclometalated iridium (Ir) complexes as the phosphorescent dopant. Energy transfer from the green Ir complex or an electroplex formed between the fluorene main chain and side-chain carbazole moieties, in addition to that from the PF main chain, to the red Ir complex can significantly enhance the device performance, and a red light-emitting device with the high efficiency 2.8 cd/A at 7 V and 65 cd/m2, comparable to that of the same Ir complex-based OLED, and a broad-band light-emitting device containing blue, green, and red peaks (2.16 cd/A at 9 V) are obtained.

Molecular design of conjugated polymers for efficient electroluminescence (EL) and color tuning has long been one of the most important subjects in the development of polymer light emitting diodes (PLED) and can be carried out in two ways: by chemical and physical methods. The chemical method, involving the incorporation of charge-transport moieties on the main chain, [1][2][3] flexible side chain, [4][5][6] and chain ends, [7] has been extensively studied for poly(phenylene vinylene)s, polyfluorenes, and other polyarylenes in order to promote balanced hole and electron fluxes and to adjust highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels, as well as the band gap for color tuning. Taking polyfluorenes as an example, incorporation of triphenylamine in the main chain and oxadiazole in the side chain provides an improvement in the efficiency and purity of blue emission to 2.07 cd A -1 and a Commission Internationale de l'Eclairage (CIE) value of x + y = 0.29, respectively, which is the best blue fluorescence device that has been reported so far.[1] However, chemical methods require elaborate synthesis.Physical methods include blending a conjugated polymer with dopants, [8][9][10] tuning a chain conformation, [11][12][13][14] and manipulating a supramolecular structure.[15] The former involves energy transfer and charge trapping allowing an enhancement of device performance in addition to color tuning and has been studied extensively. Studies on the effects of the tuning of chain conformation on EL are scarce, but studies on the effect of the manipulation of the supramolecular structure on the photoluminescence (PL) of the blue-emitting polymer poly(9,9-di-n-octyl-2,7-fluorene) (PFO) are extensive. Because of its highly coplanar backbone, PFO can be physically transformed by into a variety of supramolecular structures, [11][12][13][14] such as crystalline phases (i.e., a and a′ phase) and noncrystalline phases (such as amorphous, nematic, and b phase, which has an extended conjugation length of about 30repeat units, as evidenced by wide-angle X-ray diffraction).[16]Among these structures, b phase has attracted the most attention because of its specific physical properties, such as a lower extent of triplet exciton formation, [17] a reduced ability to be photobleached on the single-molecule scale, [18] and efficient energy transfer from the amorphous to the b phase. [19] b phase can be physically formed by dissolving PFO in solvents with lower solvent power and higher boiling points [19] or in a solvent/nonsolvent mixture (for example, chloroform/methanol), [20] by exposing a PFO film to solvent vapors (i.e., hexane, cyclohexane, tetrahydrofuran (THF), or toluene), [16] or by applying specific thermal treatment to a PFO film (cooling and reheating to room temperature). [16] In our previous work, [21] we reported that the use of an electron-deficient moiety (such as triazole) as an end-capper for PFO can induce a trace amount of b phase without any further physical treatme...

We present high efficiency and stable inverted PSCs (i-PSC) by employing sol-gel processed simultaneously doped ZnO by Indium and fullerene derivative (BisNPC60-OH) (denoted as InZnO-BisC60) film as cathode interlayer and PTB7-Th:PC71BM as the active layer (where PTB7-Th is a low bandgap polymer we proposed previously). This dual-doped ZnO, InZnO-BisC60, film shows dual and opposite gradient dopant concentration profiles, being rich in fullerene derivative at the cathode surface in contact with active layer and rich in In at the cathode surface in contact with the ITO surface. Such doping in ZnO not only gives improved surface conductivity by a factor of 270 (from 0.015 to 4.06 S cm−1) but also provides enhanced electron mobility by a factor of 132 (from 8.25*10−5 to 1.09*10−2 cm2 V−1 s−1). The resulting i-PSC exhibits the improved PCE 10.31% relative to that with ZnO without doping 8.25%. This PCE 10.31% is the best result among the reported values so far for single junction PSC.

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