The absence of near-infrared (NIR) solar cells with high open circuit voltage (V) and external quantum efficiency (EQE) has impeded progress toward achieving organic photovoltaic (OPV) power conversion efficiency PCE > 15%. Here we report a small energy gap (1.3 eV), chlorinated nonfullerene acceptor-based solar cell with PCE = 11.2 ± 0.4%, short circuit current of 22.5 ± 0.6 mA cm, V = 0.70 ± 0.01 V and fill factor of 0.71 ± 0.02, which is the highest performance reported to date for NIR single junction OPVs. Importantly, the EQE of this NIR solar cell reaches 75%, between 650 and 850 nm while leaving a transparency window between 400 and 600 nm. The semitransparent OPV using an ultrathin (10 nm) Ag cathode shows PCE = 7.1 ± 0.1%, with an average visible transmittance of 43 ± 2%, Commission d'Eclairage chromaticity coordinates of (0.29, 0.32) and a color rendering index of 91 for simulated AM1.5 illumination transmitted through the cell.

Halide perovskite films processed from solution at low‐temperature offer promising opportunities to make flexible solar cells. However, the brittleness of perovskite films is an issue for mechanical stability in flexible devices. Herein, photo‐crosslinked [6,6]‐phenylC61‐butyric oxetane dendron ester (C‐PCBOD) is used to improve the mechanical stability of methylammonium lead iodide (MAPbI3) perovskite films. Also, it is demonstrated that C‐PCBOD passivates the grain boundaries, which reduces the formation of trap states and enhances the environmental stability of MAPbI3. Thus, MAPbI3 perovskite solar cells are prepared on solid and flexible substrates with record efficiencies of 20.4% and 18.1%, respectively, which are among the highest ever reported for MAPbI3 on both flexible and solid substrates. The result of this work provides a step improvement toward stable and efficient flexible perovskite solar cells.

Organic light-emitting diodes have become a mainstream display technology because of their desirable features. Third-generation electroluminescent devices that emit light through a mechanism called thermally activated delayed fluorescence are currently garnering much attention. However, unsatisfactory device stability is still an unresolved issue in this field. Here we demonstrate that electron-transporting n-type hosts, which typically include an acceptor moiety in their chemical structure, have the intrinsic ability to balance the charge fluxes and broaden the recombination zone in delayed fluorescence organic electroluminescent devices, while at the same time preventing the formation of high-energy excitons. The n-type hosts lengthen the lifetimes of green and blue delayed fluorescence devices by > 30 and 1000 times, respectively. Our results indicate that n-type hosts are suitable to realize stable delayed fluorescence organic electroluminescent devices.

We report a simple yet versatile solution route for constructing heterojunctions from luminescent organic charge-transfer (CT) complexes through a two-step seeded-growth method. Using this method, we achieved anisotropic and selective growth of anthracene-1,2,4,5-tetracyanobenzene (TCNB) complexes onto the tips of naphthalene-TCNB microtubes, resulting in the formation of microdumbbells. Significantly, the two-component microdumbbells appear as dual-color-emitting heterojunctions arising from integration of two distinct color-emitting materials. We further elucidated the two-step seeded-growth mechanism of the dumbbell-like organic heterostructures on the basis of structural analysis of the two crystals and surface-interface energy balance. In principle, the present synthetic route may be used to fabricate a wide range of sophisticated dual- or multicolor-emitting organic heterostructures via judicious choice of the CT complexes.

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