A major challenge for organic solar cell (OSC) research is how to minimize the tradeoff between voltage loss and charge generation. In early 2019, we reported a non-fullerene acceptor (named Y6) that can simultaneously achieve high external quantum efficiency and low voltage loss for OSC. Here, we use a combination of experimental and theoretical modeling to reveal the structure-property-performance relationships of this state-of-the-art OSC system. We find that the distinctive π–π molecular packing of Y6 not only exists in molecular single crystals but also in thin films. Importantly, such molecular packing leads to (i) the formation of delocalized and emissive excitons that enable small non-radiative voltage loss, and (ii) delocalization of electron wavefunctions at donor/acceptor interfaces that significantly reduces the Coulomb attraction between interfacial electron-hole pairs. These properties are critical in enabling highly efficient charge generation in OSC systems with negligible donor-acceptor energy offset.

Adding 2-phenoxyethylamine (POEA) into a CH NH PbBr precursor solution can modulate the organic-inorganic hybrid perovskite structure from bulk to layered, with a photoluminescence and electroluminescence shift from green to blue. Meanwhile, POEA can passivate the CH NH PbBr surface and help to obtain a pure CH NH PbBr phase, leading to an improvement of the external quantum efficiency to nearly 3% in CH NH PbBr LED.

In this work, both anode and cathode interfaces of p‐i‐n CH3NH3PbI3 perovskite solar cells (PVSCs) are simultaneously modified to achieve large open‐circuit voltage (Voc) and fill factor (FF) for high performance semitransparent PVSCs (ST‐PVSCs). At the anode, modified NiO serves as an efficient hole transport layer with appropriate surface property to promote the formation of smooth perovskite film with high coverage. At the cathode, a fullerene bisadduct, C60(CH2)(Ind), with a shallow lowest unoccupied molecular orbital level, is introduced to replace the commonly used phenyl‐C61‐butyric acid methyl ester (PCBM) as an alternative electron transport layer in PVSCs for better energy level matching with the conduction band of the perovskite layer. Therefore, the Voc, FF and power conversion efficiency (PCE) of the PVSCs increase from 1.05 V, 0.74 and 16.2% to 1.13 V, 0.80 and 18.1% when the PCBM is replaced by C60(CH2)(Ind). With the advantages of high Voc and FF, ST‐PVSCs are also fabricated using an ultrathin transparent Ag as cathode, showing an encouraging PCEs of 12.6% with corresponding average visible transmittance (AVT) over 20%. These are the highest PCEs reported for ST‐PVSCs with similar AVTs paving the way for using ST‐PVSCs as power generating windows.

A new amino-functionalized polymer, PN4N, was developed and applied as an efficient interlayer to improve the cathode interface of fullerene/perovskite (CH3NH3PbIxCl3−x) planar heterojunction solar cells.

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effi ciency (PCE) of the record perovskite solar cells (PVSCs) has already reached over 20%, [ 6 ] making it a potential contender for new generation photovoltaic technology.The perovskite semiconductors can be adopted in various types of solar cell architectures including perovskite-sensitized solar cells, [ 1 ] meso-superstructured solar cells and planar heterojunction (PHJ) solar cells. [ 7,8 ] The latter one, which has a device architecture resembles that of polymer solar cells, is particularly attractive for potential commercialization due to the simplicity of the device structure, low-temperature solution processibility, as well as the potential of large-scale manufacturing using a continuous coating technique on fl exible substrates. [8][9][10][11][12][13][14] The most commonly used inverted device architecture for PHJ PVSCs is ITO/ poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS)/perovskite/ phenyl-C61-butyric acid methyl ester (PC 61 BM)/metal, in which the PEDOT:PSS and PC 61 BM serve as hole-transporting layer (HTL) and electron-transporting layer (ETL), respectively. Recent advances in optimizing the perovskite morphology and cathode interface have resulted in high PCE in the PEDOT:PSSbased PVSCs. [15][16][17][18][19][20][21][22][23] However, the open-circuit voltage ( V oc ) (0.90-0.95 V) in the PEDOT:PSS-based PVSCs is typically lower than that (≈1.05 V) obtained from meso-superstructured PVSCs due to the mismatched workfunction between PEDOT:PSS and the valence band of perovskite semiconductor. Therefore, new anode modifi cation is also important to fully unveil the potential of inverted PHJ PVSCs. [ 3,7,[24][25][26][27] Although several inorganicbased HTLs have been exploited to enhance the V oc and PCE of PHJ PVSCs, the severe surface charge recombination due to the presence of surface traps in the metal oxide limits their performance and the high temperature sintering process (>300 °C) required for preparing oxide fi lms with high crystallinity make it incompatible for roll-to-roll printing process and limits its practical applications. [ 12,[28][29][30][31] PEDOT:PSS is generally used as anode interlayer because of its solution processibility, good electrical property, low processing temperature, and commercial availability. Nevertheless,

The field of organic-inorganic hybrid perovskite light-emitting diodes (PeLEDs) has developed rapidly in recent years. Although the performance of PeLEDs continues to improve through film quality control and device optimization, little research has been dedicated to understanding the recombination dynamics in perovskite thin films. Likewise, little has been done to investigate the effects of recombination dynamics on the overall light-emitting behavior of PeLEDs. Therefore, this study investigates the recombination dynamics of CH NH PbI thin films with differing crystal sizes by measurement of fluence-dependent transient absorption dynamics and time-resolved photoluminescence. The aim is to find out the link between recombination dynamics and device behavior in PeLEDs. It is found that bimolecular and Auger recombination become more efficient as the crystal size decreases and monomolecular recombination rate is affected by the trap density of perovskite. By defining the radiative efficiency Φ(n), which relates to the monomolecular, bimolecular, and Auger recombination, the fundamental recombination properties of CH NH PbI films are discerned in quantitative terms. These findings help us to understand the light emission behavior of PeLEDs. This study takes an important step toward establishing the relationship between film structure, recombination dynamics, and device behavior for PeLEDs, thereby providing useful insights toward the design of better perovskite devices.

As a promising cathode material of sodium-ion battery, P2-type NaNiMnO (NNMO) possesses a theoretically high capacity and working voltage to realize high energy storage density. However, it still suffers from poor cycling stability mainly incurred by the undesirable P2-O2 phase transition. Herein, the electrochemically active Fe ions are introduced into the lattice of NNMO, forming NaNiMnFe O ( x = 0, 1/24, 1/12, 1/8, 1/6) to effectively stabilize the P2-type crystalline structure. In such Fe-substituted materials, both Ni/Ni and Fe/Fe couples take part in the redox reactions, and the P2-O2 phase transition is well restrained during cycling, as verified by ex situ X-ray diffraction. As a result, the optimized NaNiMnFeO (1/12-NNMF) has a long-term cycling stability with the fading rate of 0.05% per cycle over 300 cycles at 5 C. Furthermore, the 1/12-NNMF delivers excellent rate capabilities (65 mA h g at 25 C) and superior low-temperature performance (the capacity retention of 94% at -25 °C after 80 cycles) owing to the enhanced Na diffusion upon Fe doping, which is deduced by the studies of electrode kinetics. More significantly, the 1/12-NNMF also displays remarkable sodium-ion full-cell properties when merged with an LS-Sb@G anode, thus implying the possibility of their practical application.