A significant enhancement in ultraviolet (UV) durable indium tin oxide (ITO)-free flexible nonfullerene organic solar cells (OSCs) has been demonstrated using a hybrid nanostructured flexible transparent electrode (FTE), comprising a mixture of 0D silver nanoparticles (AgNPs), 1D Ag nanowires (AgNWs) and 2D exfoliated graphene sheets. The FTE exhibits high optical transparency and electric conductivity, good air stability and full-solution fabrication capability at a low processing temperature. An average power convention efficiency (PCE) of 8.15% has been obtained for the flexible nonfullerene OSCs, based on the blend of poly[(2,6-(4, 8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thi enyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c'] dithiophene-4,8-dione)] (PBDB-T): 3,9bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dit hieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b'] dithiophene (ITIC). The flexible PBDB-T:ITIC OSCs exhibit an excellent UV durability compared to the ITO-based control cell, realized by the tailored FTE absorption in wavelength < 380 nm. The novel FTE developed in this work provides a promising alternative to ITO for use in UV durable flexible OSCs, serving as a UV filter to impede an unavoidable UV-induced degradation in ITO-based OSCs.

commercialization of OLEDs, especially for the application in lighting, [6] but it is often hard to achieve both. High brightness requires high current density, [7] and the accompanying high temperature and Coulombic force degradation will greatly shorten the lifetime. [8][9][10][11][12] Tandem configuration, by using a charge generation layer (CGL) to connect several OLED units in series, is a practical strategy to optimize the lifetime of OLEDs while maintaining high luminance. [13,14] Under the same luminance, the current of each OLED unit can be reduced in the tandem structure, which efficiently extends the lifetime of the tandem OLEDs.CGLs in tandem OLEDs can separate carriers well and inject them into adjacent functional layers, functioning as a connector between the emitting units. [15,16] At present, CGLs are commonly based on metal, conductive oxides, and transition metal oxides, such as 4,7-diphenyl-1,10-phenanthroline (Bphen):Cs 2 CO 3 , N,N′-bis-(1-naphthalenyl)-N, N′-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine (NPB):MoO 3 , and Bphen:Li. [17][18][19][20][21][22][23] On the other hand, organic p-n heterojunctions can also be used as the CGL. [24][25][26] The exciton can separate at the interface of the p-n junction induced by the external electric field so that electrons from the highest occupied molecular orbital (HOMO) of the p-type material can easily inject into the lowest unoccupied molecular orbital (LUMO) of the n-type material due to the small injection barrier. [15,27] In addition, the doped n-type material will simultaneously produce a much higher electron concentration, which facilitates the electron concentration and injection. [28,29] On the other hand, doped p-type material will induce an increase in the electrical conductivity caused by a charge transfer between the dopant and the p-type material, which will lead to an increase in the free hole concentration and hole injection. [28] Therefore, the performance of the tandem OLEDs can be significantly enhanced.Compared with the traditional tandem OLEDs, the inverted tandem OLEDs can well protect the water-and oxygen-sensitive n-type layer, thus obtaining a longer lifetime.

Ultraviolet (UV)‐durable organic solar cells (OSCs) are realized by incorporating a CdSe@ZnS quantum dots (QDs)‐modified PEDOT:PSS hole extraction layer (HEL). The use of the CdSe@ZnS QDs‐modified PEDOT:PSS HEL has an obvious improvement in UV‐durability of OSCs. A more than 50% reduction in the power conversion efficiency (PCE) is observed for a (PM6:Y6)‐based control OSC with a PEDOT:PSS HEL, under the 1000 min accelerated UV (365 nm, 16 W) aging test. Whereas a much reduced reduction of 35% in PCE is observed for the OSCs with a CdSe@ZnS QDs‐modified PEDOT:PSS HEL, under the same accelerated UV aging test condition. Results reveal that the Coulombic attraction between the PEDOT units and PSS chains in the PEDOT:PSS layer is disturbed due to the interaction between hydroxyl ligands of the CdSe@ZnS QDs and PSS through hydrogen bond, leading to an increase in the electric conductivity in PEDOT:PSS layer through transforming PEDOT quinoid structure to expanded‐coil structure. The use of the CdSe@ZnS QDs‐modified PEDOT:PSS HEL also favors the efficient operation of the nonfullerene acceptor (NFA)‐based OSCs through maintaining a high built‐in potential across the bulk heterojunction. The results demonstrate the importance of the interface engineering to alleviate UV light‐induced degradation processes of NFA‐based OSCs.

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