Tin oxide (SnO 2 ) electron selective layers (ESLs) processed by low-temperature plasma-enhanced atomic layer deposition (PEALD) hold promise for fabricating lightweight and efficient flexible lead halide perovskite solar cells (PVSCs). However, the as-synthesized SnO 2 ESLs typically lead to flexible PVSCs with lower open-circuit voltage (V OC ) and fill factor (FF) as well as a higher degree of current density−voltage (J−V) hysteresis, compared to PVSCs fabricated on rigid substrates. Here, we report that facile water vapor treatment of PEALD-synthesized SnO 2 ESLs can effectively improve the V OC and FF while reducing the degree of J−V hysteresis. The improvement in device performance is mainly attributed to the improved conductivity and electrical mobility of SnO 2 ESLs enabled by water vapor treatment. With such treatment, our best flexible PVSC fabricated on a commercial substrate shows a power conversion efficiency of 18.36 (17.12)% when measured under a reverse (forward) voltage scan and a stabilized efficiency of 17.08%, which is the highest reported efficiency for flexible PVSCs with the regular structure.

A highly efficient QLED achieving white emission at a low driving voltage is obtained by employing Zn0.95Mg0.05O as the electron transport layer.

We report an inverted and multilayer quantum dot light emitting diode (QLED) which boosts high efficiency by tuning the energy band alignment between charge transport and light emitting layers. The electron transport layer (ETL) was ZnO nanoparticles (NPs) with an optimized doping concentration of cesium azide (CsN) to effectively reduce electron flow and balance charge injection. This is by virtue of a 0.27 eV upshift of the ETL's conduction band edge, which inhibits the quenching of excitons and preserves the superior emissive properties of the quantum dots due to the insulating characteristics of CsN. The demonstrated QLED exhibits a peak current efficiency, power efficiency and external quantum efficiency of up to 13.5 cd A, 10.6 lm W and 13.4% for the red QLED, and correspondingly 43.1 cd A, 33.6 lm W and 9.1% for green, and 4.1 cd A, 2.0 lm W and 6.6% for the blue counterparts. Compared with QLEDs without optimization, the performance of these modified devices shows drastic improvement by 95.6%, 39.4% and 36.7%, respectively. This novel device architecture with heterogeneous energy levels reported here offers a new design strategy for next-generation high efficiency QLED displays and solid-state lighting technologies.

A highly efficient solution-processed QLED device with a doped HTL has been demonstrated by the modulation of hole transport.

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