Operating in wet conditions: The high efficiency of the complex organic molecule Spiro-OMeTAD as a hole-transporting material for perovskite solar cells requires the use of hygroscopic dopants that decrease stability. Jeong et al. synthesized hydrophobic fluorinated analogs of Spiro-OMeTAD as hole-transporting materials that have favorable shifting of the electronic state for hole extraction and used them to fabricate perovskite solar cells. A champion device had a certified power conversion efficiency of 24.8% and an open-circuit voltage near the Shockley-Queisser limit. These devices could maintain more than 87% of the original power conversion efficiency under 50% relative humidity for more than 500 hours. Science , this issue p. 1615

In this study, we propose an effective strategy for achieving the flexible one organic transistor–one organic memristor (1T–1R) synapse using the multifunctional organic memristor. The dynamics of the conductive nanofilament (CF) in a hydrophobic fluoropolymer medium is explored and a hydrophobic fluoropolymer-based organic memristor is developed. The flexible 1T–1R synapse can be fabricated using the solution process because the hydrophobic fluorinated polymer layer is produced on the organic transistor without degradation of the underlying semiconductor. The developed flexible synapse exhibits multilevel conductance with high reliability and stability because of the fluoropolymer film, which acts as a medium for CF growth and an encapsulating layer for the organic transistor. Moreover, the synapse cell shows potential for high-density memory systems and practical neural networks. This effective concept for developing practical flexible neural networks would be a basic platform to realize the smart wearable electronics.

Y-doped SnO₂ thin film transistors were successfully fabricated by means of sol-gel process. The effect of Y concentration on the structural, chemical, and electrical properties of sol-gel-processed SnO₂ films was investigated via GIXRD, SPM, and XPS; the corresponding electrical transport properties of the film were also evaluated. The dopant, Y, can successfully control the free carrier concentration by suppressing the formation of oxygen vacancy inside SnO₂ semiconductors due to its lower electronegativity and SEP. With an increase of Ywt%, it was observed that the crystallinity and oxygen vacancy concentration decreased, and the operation mode of SnO₂ thin film transistor changed from accumulation (normally on) to enhancement mode (normally off) with a positive V_th shift.

Thin‐film solar cells based on hydrogenated amorphous silicon (a‐Si:H) and conjugated polymers have been studied extensively. However, organic–inorganic hybrid tandem solar cells incorporating the two materials as subcells are yet to be extensively studied. Here, a computational study on the optimal design of organic–inorganic hybrid tandem solar cells to achieve the maximum possible efficiency is presented. The optical simulations predict the optimal design of an organic–inorganic hybrid tandem solar cell, desirable for a wide range of spectral response and high efficiency. The optimum combination of thicknesses of a‐Si:H and organic photovoltaic (OPV) subcells to achieve the highest possible efficiency in terms of short circuit current ( J _sc ) is determined. Thicknesses of 400 and 140 nm for a‐Si:H and OPV subcells, respectively, are suggested for the optimised tandem solar cell to achieve current matching and a maximum power conversion efficiency of 11.57%.

We attempted surface modification in ZnO nanoparticles (NPs) synthesized by the sol–gel process with polyvinyl pyrrolidone (PVP) applied to bulk-heterojunction polymer solar cells (PSCs) as an electron transport layer (ETL). In general, ZnO NPs have trap sites due to oxygen vacancies which capture electrons and degrade the performance of the PSCs. Devices with six different PVP:Zn ratios (0.615 g, 1.230 g, 1.846 g, 2.460 g, 3.075 g, and 3.690 g) were fabricated for surface modification, and the optimized PVP:Zn ratio (2.460 g) was found for PSCs based on P3HT/PCBM. The power conversion efficiency (PCE) of the fabricated PSCs with PVP-capped ZnO exhibited a significant increase of approximately 21% in PCE and excellent air-stability as compared with the uncapped ZnO-based PSCs.