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Mixed Pb-In perovskite solar cells are fabricated by using lead(II) chloride and indium(III) chloride with methylammonium iodide. A maximum power conversion efficiency as high as 17.55% is achieved owing to the high quality of perovskites with multiple ordered crystal orientations.

The development of effective and stable hole transporting materials (HTMs) is very important for achieving high‐performance planar perovskite solar cells (PSCs). Herein, copper salts (cuprous thiocyanate (CuSCN) or cuprous iodide (CuI)) doped 2,2,7,7‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9‐spirobifluorene (spiro‐OMeTAD) based on a solution processing as the HTM in PSCs is demonstrated. The incorporation of CuSCN (or CuI) realizes a p‐type doping with efficient charge transfer complex, which results in improved film conductivity and hole mobility in spiro‐OMeTAD:CuSCN (or CuI) composite films. As a result, the PCE is largely improved from 14.82% to 18.02% due to obvious enhancements in the cell parameters of short‐circuit current density and fill factor. Besides the HTM role, the composite film can suppress the film aggregation and crystallization of spiro‐OMeTAD films with reduced pinholes and voids, which slows down the perovskite decomposition by avoiding the moisture infiltration to some extent. The finding in this work provides a simple method to improve the efficiency and stability of planar perovskite solar cells.

Significant effort has been made to develop novel material systems to improve the efficiency of near‐infrared organic light‐emitting diodes (NIR OLEDs). Of those, fluorescent chromophores are mostly studied because of their advantages in cost and tunability. However, it is still rare for fluorescent NIR emitters to present good color purities in the NIR range and to have high external quantum efficiency (EQE). Here, a wedge‐shaped D‐π‐A‐π‐D emitter APDC‐DTPA with thermally activated delayed fluorescence property and a small single‐triplet splitting (ΔEst) of 0.14 eV is presented. The non‐doped NIR device exhibits excellent performance with a maximum EQE of 2.19% and a peak wavelength of 777 nm. Remarkably, when 10 wt% of APDC‐DTPA is doped in 1,3,5‐tris(1‐phenyl‐1H‐benzimidazol‐2‐yl)benzene host, an extremely high EQE of 10.19% with an emission peak of 693 nm is achieved. All these values represent the best result for NIR OLEDs based on a pure organic fluorescent emitter with similar device structure and color gamut.

via endothermally assisted reverse intersystem crossing (RISC), thereby achieving a theoretical 100% exciton utilization. [1b,3,4] The strategy for a sufficiently small ΔE ST is to reduce the electron exchange of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) by separating them into different segments. [5][6][7][8] As a classic example, a donor-π-acceptor (D-π-A) molecular architecture can form a twisted conformation at excitation and induce effective charge transfer (CT) along with the HOMO (@ donor) and LUMO (@ acceptor) separation. [6,9] The structure relaxation between the ground and twist induced excited states, however, inevitably results in large Stokes shift and broad CT emission, which is extremely detrimental to the color purity of the emitters for high-resolution display applications.In an exceptional solution for this problem proposed by Hatakeyama et al., a series of N/B rigid heterocycles were used as multiple resonances induced TADF (MR-TADF) emitters based on a DABNA-1 core to show good color purity. [10] Different from the D-π-A type TADF emitters, these MR-TADF emitters possess a rigid configuration and realize the HOMO and LUMO separation by opposite resonance effect of the nitrogen and boron atoms. Very recently, by modifying the original DABNA-1 with a peripheral carbazole group, Zheng and co-workers obtained a more efficient MR-TADF emitter TBN-TPA, and the corresponding device realized a maximum external quantum efficiency (EQE max ) of 32.1% and a sharp blue emission peak with full-width at half-maximum (FWHM) of 27 nm, showing the potential of MR-TADF. [11] However, the attempts with oxygen atoms replacing nitrogen atoms as the electron-donating group in a polycyclic framework did not activate the TADF phenomenon, [12] indicating new MR-TADF systems need more investigation and the versatility of the molecular design should be further explored.In this work, we design a novel system bearing MR-TADF activity aside from the reported N/B system, which consists of rigidified aryl ketones and amine. In the previous study, carbonyl group was widely used as a functional motif for room temperature phosphorescent materials and TADF emitters, owing to the electron-withdrawing nature and the small ΔE ST caused by its electronic transition from the n orbital to Multiple resonances induced thermally activated delayed fluorescence (MR-TADF) has great advantages in high color purity display. Up to now, current MR-TADF emitters are only based on the boron-nitrogen-containing fragment. Reported herein is a novel class of MR-TADF emitter, quinolino[3,2,1-de]acridine-5,9-dione (QAO), realized by the opposite resonance effect of the carbonyl and the nitrogen atoms, which is also the smallest TADF emitter reported so far. The QAO-based pure blue organic light-emitting diode achieves a maximum external quantum efficiency (EQE max ) of 19.4% with a small full width at half maximum of 39 nm. Moreover, tert-butyl modified QAO can be employed as an efficient electr...

Vacuum-evaporated all-inorganic cesium lead bromine perovskite LEDs achieved a maximum external quantum efficiency of 1.55%.

PSS) and CH3NH3PbIxCl3-x. In addition, perylene and perovskites form a fully crystalline heterojunction, which is beneficial for minimizing the defect and trap densities. Due to these merits, a maximum power conversion efficiency of 17.06% with improved cell stability is achieved. The finding in this work provides a simple route to control perovskite crystallizaition and to optimize the interfaces in PHJ PSCs simultaneously.

The fabrication and device parameters of inverted planar heterojunction (PHJ) organic–inorganic lead mixed-halide (CH3NH3PbI3−xClx) perovskite based solar cells (PSCs) using a:CuAlO2 as the hole selective buffer layer between the ITO electrode and PEDOT:PSS were demonstrated.