Nonfullerene acceptors tend to decompose in the presence of ZnO due to photocatalytic activity, and SnO2 is an alternative for higher efficiency and better stability.

No abstract

Achieving high power conversion efficiency and good mechanical robustness is still challenging for the ultraflexible organic solar cells. Interlayers simultaneously having good mechanical robustness and good chemical compatibility with the active layer are highly desirable. In this work, we present an interlayer of Zn2+-chelated polyethylenimine (denoted as PEI-Zn), which can endure a maximum bending strain over twice as high as that of ZnO and is chemically compatible with the recently emerging efficient nonfullerene active layers. On 1.3 μm polyethylene naphthalate substrates, ultraflexible nonfullerene solar cells with the PEI-Zn interlayer display a power conversion efficiency of 12.3% on PEDOT:PSS electrodes and 15.0% on AgNWs electrodes. Furthermore, the ultraflexible cells show nearly unchanged power conversion efficiency during 100 continuous compression-flat deformation cycles with a compression ratio of 45%. At the end, the ultraflexible cell is demonstrated to be attached onto the finger joint and displays reversible current output during the finger bending-spreading.

All‐solution‐processed organic solar cells (from the bottom substrate to the top electrode) are highly desirable for low‐cost and ubiquitous applications. However, it is still challenging to fabricate efficient all‐solution‐processed organic solar cells with a high‐performance nonfullerene (NF) active layer. Issues of charge extraction and wetting are persistent at the interface between the nonfullerene active layer and the printable top electrode (PEDOT:PSS). In this work, efficient all‐solution‐processed NF organic solar cells (from the bottom substrate to the top electrode) are reported via the adoption of a layer of hydrogen molybdenum bronze (HXMoO3) between the active layer and the PEDOT:PSS. The dual functions of HXMoO3 include: 1) its deep Fermi level of −5.44 eV can effectively extract holes from the active layer; and 2) the wetting issues of the PEDOT:PSS on the hydrophobic surface of the NF active layer can be solved. Importantly, fine control of the HXMoO3 composition during the synthesis is critical in obtaining processing orthogonality between HXMoO3 and the PEDOT:PSS. Flexible all‐solution‐processed NF organic solar cells with power conversion efficiencies of 11.9% and 10.3% are obtained for solar cells with an area of 0.04 and 1 cm2, respectively.

Thick, uniform, easily processed, highly conductive polymer films are desirable as electrodes for solar cells as well as polymer capacitors. Here, a novel scalable strategy is developed to prepare highly conductive thick poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (HCT-PEDOT:PSS) films with layered structure that display a conductivity of 1400 S cm(-1) and a low sheet resistance of 0.59 ohm sq(-1). Organic solar cells with laminated HCT-PEDOT:PSS exhibit a performance comparable to the reference devices with vacuum-deposited Ag top electrodes. More importantly, the HCT-PEDOT:PSS film delivers a specific capacitance of 120 F g(-1) at a current density of 0.4 A g(-1). All-solid-state flexible symmetric supercapacitors with the HCT-PEDOT:PSS films display a high volumetric energy density of 6.80 mWh cm(-3) at a power density of 100 mW cm(-3) and 3.15 mWh cm(-3) at a very high power density of 16160 mW cm(-3) that outperforms previous reported solid-state supercapacitors based on PEDOT materials.

Development of large‐area flexible organic solar cells (OSCs) is highly desirable for their practical applications. However, the efficiency of the large‐area flexible OSCs severely lags behind small‐area devices. Here, efficient large‐area flexible single cells with power conversion efficiency (PCE) of 13.1% and 12.6% for areas of 6 and 10 cm2, and flexible modules with a PCE of 13.2% (54 cm2) based on poly(ethylene terephthalate)/Ag grid/silver nanowires (AgNWs):zinc‐chelated polyethylenimine (PEI‐Zn) composite electrodes are reported. The solution‐processed flexible transparent electrode of AgNWs:PEI‐Zn shows low surface roughness and good optoelectronic and mechanical properties. PEI‐Zn is conductive and optically transparent. It can adhere to and wrap the AgNWs under electrostatic interaction between the negatively charged surface (AgNWs) and positively charged protonated amine groups (in PEI‐Zn). It wraps the AgNWs networks and fills the void space to achieve a smooth surface. The flexible electrode is validated in both flexible OSCs and flexible quantum‐dots light‐emitting diodes (QLEDs). Small‐area flexible OSCs show a PCE of 16.1%, and flexible QLEDs show an external quantum efficiency of 13.3%. In the end, a flexible module is demonstrated to charge a mobile phone as a flexible power source (shown in Video S1, Supporting Information).

Flexible non-fullerene organic solar cells based on AgNWs embedded in polyimide substrates demonstrate a high efficiency up to 11.6%.

It is still challenging to fabricate efficient large-area organic solar modules by solution processing. Processing window is important to obtain optimal aggregation of an active layer in large area for high efficiency. The star active layer of PM6:Y6 is processed from chloroform (for high efficiency) that has a narrow processing window due to the low boiling point of the solvent. In this work, the correlation between chemical structure (side chains) and processing solvents is investigated to obtain high efficiency and long processing windows. It is found that large side chains on the pyrrole ring are the key factor influencing the aggregation of active layer films. Short side chain (in Y6 and Y6-1O) will cause excess aggregation when processed from high-boiling-point solvent (chlorobenzene, CB), while long side-chain (in BTP-BO-4F, BTP-BO-4Cl, and BTP-eC9) can inhibit such aggregation and maintain high photovoltaic performance when processed from CB with wide processing window. In the end, over 25 cm 2 organic solar module via doctor blading based on PM6:BTP-eC9 active layer has been fabricated with a PCE of 14.07%.