Core-shell carbon-polymer quantum dot passivation for near infrared perovskite light emitting diodes

High-performance perovskite light-emitting diodes (PeLEDs) require a high quality perovskite emitter and appropriate charge transport layers to facilitate charge injection and transport within the device. Solution-processed n-type metal oxides represent a judicious choice for the electron transport layer (ETL); however, they don't always present suitable surface properties and energetics in order to be compatible with the perovskite emitter. Moreover, the emitter itself exhibits poor nanomorphology and defect traps that compromise the device performance. Here we modulate the surface properties and interface energetics of the tin oxide (SnO2) ETL with the perovskite emitter by using an amino functionalized difluoro{2-[1-(3,5-dimethyl-2H-pyrrol-2-ylidene-N)ethyl]-3,5-dimethyl-1H-pyrrolato-N}boron (BDP) compound and passivate the defects present in the perovskite with carbon-polymer core-shell quantum dots (PCDs) inserted into the perovskite precursor. Both these approaches synergistically improve the perovskite layer nanomorphology and enhance the radiative recombination. These properties resulted in the fabrication of near infrared (NIR) PeLEDs based on formamidinium lead iodide (FAPbI3) with a high radiance of 92 W sr-1 m-2, an external quantum efficiency (EQE) of 14% and reduced efficiency roll-off

Strain relaxation and multidentate anchoring in n-type perovskite transistors and logic circuits

This is the author accepted manuscriptData availability: Source data are provided with this paper. Additional data related to this work are available from the corresponding authors upon request.Code availability statement: All codes (software) used in the calculation and visualization are publicly available and the condition of their usage in the publication is an appropriate citation.The engineering of tin halide perovskites has led to the development of p-type transistors with field-effect mobilities of over 70 cm2 V-1 s-1 . However, due to their background hole doping, these perovskites are not suitable for n-type transistors. Ambipolar lead halide perovskites are potential candidates, but their defective nature limits electron mobilities to around 3-4 cm2 V-1 s-1, which makes the development all-perovskite logical circuits challenging. Here, we report formamidinium lead iodide perovskite n-type transistors with field-effect mobilities of up to 33 cm2 V-1s-1 measured in continuous bias mode. This is achieved through strain relaxation of the perovskite lattice using a methyl ammonium chloride additive, followed by suppression of undercoordinated lead through tetramethyl ammonium fluoride multidentate anchoring. Our approach stabilizes the alpha phase, balances strain, and improves surface morphology, crystallinity, and orientation. It also enables low-defect perovskite–dielectric interfaces. We use 46 the transistors to fabricate unipolar inverters and eleven-stage ring oscillator

Semi-crystalline photovoltaic polymers with siloxane-terminated hybrid side-chains

Three types of semi-crystalline photovoltaic polymers were synthesized by incorporating a siloxane-terminated organic/inorganic hybrid side-chain and changing the number of fluorine substituents. A branch point away from a polymer main backbone in the siloxane-containing side-chains and the intra- and/or interchain noncovalent coulombic interactions enhance a chain planarity and facile interchain organization. The resulting polymers formed strongly agglomerated films with high roughness, suggesting strong intermolecular interactions. The optical band gap of ca. 1.7 eV was measured for all polymers with a pronounced shoulder peak due to tight ??-?? stacking. With increasing the fluorine substituents, the frontier energy levels decreased and preferential face-on orientation was observed. The siloxane-terminated side-chains and fluorine substitution promoted the intermolecular packing, showing well resolved lamellar scatterings up to (300) for this series of polymers in the grazing incidence wide angle X-ray scattering measurements. The PPsiDTBT, PPsiDTFBT and PPsiDT2FBT devices showed a power conversion efficiency of 3.16%, 4.40% and 5.65%, respectively, by blending with PC71BM. Langevin-type bimolecular charge recombination was similar for three polymeric solar cells. The main loss in the photocurrent generation for PPsiDTBT:PC71BM was interpreted to originate from the trap assisted charge recombination by measuring light-intensity dependent short-circuit current density (Jsc) and open-circuit voltage (Voc). Our results provide a new insight into the rational selection of solubilizing substituents for optimizing crystalline interchain packing with appropriate miscibility with PC71BM for further optimizing polymer solar cells.clos