lizhendong

An aqueous-solution-processed photoconductive cathode interlayer is developed, in which the photoinduced charge transfer brings multiple advantages such as increased conductivity and electron mobility, as well as reduced work function. Average power conversion efficiency over 10% is achieved even when the thickness of the cathode interlayer and active layer is up to 100 and 300 nm, respectively.

Over the past five years, a rapid progress in organometal-halide perovskite solar cells has greatly influenced emerging solar energy science and technology. In perovksite solar cells, the overlying hole transporting material (HTM) is critical for achieving high power conversion efficiencies (PCEs) and for protecting the air-sensitive perovskite active layer. This study reports the synthesis and implementation of a new polymeric HTM series based on semiconducting 4,8-dithien-2-yl-benzo[1,2-d;4,5-d′]bistriazole-alt-benzo[1,2-b:4,5-b′]dithiophenes (pBBTa-BDTs), yielding high PCEs and environmentally-stable perovskite cells. These intrinsic (dopant-free) HTMs achieve a stabilized PCE of 12.3% in simple planar heterojunction cells—the highest value to date for a polymeric intrinsic HTM. This high performance is attributed to efficient hole extraction/collection (the most efficient pBBTa-BDT is highly ordered and orients π-face-down on the perovskite surface) and balanced electron/hole transport. The smooth, conformal polymer coatings suppress aerobic perovskite film degradation, significantly enhancing the solar cell 85 °C/65% RH PCE stability versus typical molecular HTMs.

New in-chain donor–acceptor semiconducting copolymers are designed and synthesized as dopant-free perovskite solar cell hole transport materials. Combining the BDT donor and the BBTa acceptor building blocks yields pBBTa-BDT copolymers with strong interchain interactions, substantial quinoidal π-character, preferential π-face-on orientation, and therefore efficient hole extraction/collection and balanced electron/hole transport. Significant enhancement of solar cell performance and environmental stability are achieved.

The strong ionic character endows all-inorganic CsPbX₃ (X = Cl, Br, I) perovskite nanocrystals (NCs) with different chemical features from classical Cd-based NCs, especially when considering their interaction with polar solvents and surfactants. This has aroused intensive interest, but is still short of comprehensive understanding. More significantly, above characteristic may be used to improve the quality of perovskite thin films, which is crucial for the carrier transport inside optoelectronic devices. Here, an interesting recyclable dissolution–recyrstallization phenomenon of all-inorganic pervoskite, as well as its application on room temperature (RT) self-healing of compact and smooth carrier channels in ambient atmosphere for high-performance PDs with high stability is reported. First, according to solubility equilibrium principle, the size of CsPbBr₃ crystals can be reversibly tuned in the range of 10 nm–1 μm through washing with polar solvent or stirring with assistance of surfactants at RT. Second, such phenomenon is applied for significant film quality improvement by forming a liquid circumstance within films, which can transport matter at surface and sharp parts into the gaps, healing themselves at RT. This strategy results in large-area, crack-free, low-roughness perovskite thin films. Obviously, such improvement facilitates transport and extraction of carriers in the channels of devices, which has been evidenced by the improvement of performances of the corresponding PDs at ambient condition.

An interesting surface chemical phenomenon of all-inorganic perovskite—recyclable dissolution and recrystallization—is reported, which is applied to build compact and smooth carrier channels for optoelectronic devices via self-healing under ambient condition. The advantages of this film treating strategy are convinced by the improved responsivity, external quantum efficiency, response speed, and stability of photodetectors.

The first visible-blind UV photodetector based on MAPbCl₃ integrated on a substrate exhibits excellent performance, with responsivities reaching 18 A W⁻¹ below 400 nm and imaging-compatible response times of 1 ms. This is achieved by using substrate-integrated single crystals, thus overcoming the severe limitations affecting thin films and offering a new application of efficient, solution-processed, visible-transparent perovskite optoelectronics.

Organo-lead halide perovskite solar cells (PSCs) have received great attention because of their optimized optical and electrical properties for solar cell applications. Recently, a dramatic increase in the photovoltaic performance of PSCs with organic hole transport materials (HTMs) has been reported. However, as of now, future commercialization can be hampered because the stability of PSCs with organic HTM has not been guaranteed for long periods under conventional working conditions, including moist conditions. Furthermore, conventional organic HTMs are normally expensive because material synthesis and purification are complicated. It is herein reported, for the first time, octadecylamine-capped pyrite nanoparticles (ODA-FeS₂ NPs) as a bi-functional layer (charge extraction layer and moisture-proof layer) for organo-lead halide PSCs. FeS₂ is a promising candidate for the HTM of PSCs because of its high conductivity and suitable energy levels for hole extraction. A bi-functional layer based on ODA-FeS₂ NPs shows excellent hole transport ability and moisture-proof performance. Through this approach, the best-performing device with ODA-FeS₂ NPs-based bi-functional layer shows a power conversion efficiency of 12.6% and maintains stable photovoltaic performance in 50% relative humidity for 1000 h. As a result, this study has the potential to break through the barriers for the commercialization of PSCs.

A bi-functional layer based on hydrophobic ligand capped FeS₂ nanoparticles is an outstanding inorganic hole transporting materials (HTMs) for perovskite solar cells (PSCs). PSCs with FeS₂ bi-functional layer show high photovoltaic performance and improved long-term stability because HTMs based on FeS₂ have excellent hole transport ability and moisture-proof performance. Our approach will contribute to reliability improvement of PSCs.

A profound understanding of the photophysical processes at donor/acceptor interfaces is integral for the optimization of the photo conversion efficiency (PCE) of solar cell devices. Time-resolved laser spectroscopy and electron microscopic investigations provide the key information to accomplish high PCE in polymer-fullerene-based solar cells. This device optimization enhanced the PCE from 2% in IC₆₀BA-based to >9% in PC₇₁BM-based solar cells, as presented by Omar F. Mohammed and co-workers in article number 1502356.

A novel crosslinkable amino-functionalized conjugated polymer PFN-V is used as the cathode interlayer for high performance polymer solar cells, as reported by Lei Ying, Fei Huang, and co-workers in article number 1502563. The film can be rapidly crosslinked by UV-curing within 5 s in a nearly quantitative yield based on “thiol-ene” click reaction. This time- and labor-saving strategy may have practical applications in high throughput industrial production.

Molecular orientation, with respect to donor/acceptor interface and electrodes, plays a critical role in determining the performance of all-polymer solar cells (all-PSCs), but is often difficult to rationally control. Here, an effective approach for tuning the molecular crystallinity and orientation of naphthalenediimide-bithiophene-based n-type polymers (P(NDI2HD-T2)) by controlling their number average molecular weights (M_n) is reported. A series of P(NDI2HD-T2) polymers with different M_n of 13.6 (P_L), 22.9 (P_M), and 49.9 kg mol⁻¹ (P_H) are prepared by changing the amount of end-capping agent (2-bromothiophene) during polymerization. Increasing the M_n values of P(NDI2HD-T2) polymers leads to a remarkable shift of dominant lamellar crystallite textures from edge-on (P_L) to face-on (P_H) as well as more than a twofold increase in the crystallinity. For example, the portion of face-on oriented crystallites is dramatically increased from 21.5% and 46.1%, to 78.6% for P_L, P_M, and P_H polymers. These different packing structures in terms of the molecular orientation greatly affect the charge dissociation efficiency at the donor/acceptor interface and thus the short-circuit current density of the all-PSCs. All-PSCs with PTB7-Th as electron donor and P_H as electron acceptor show the highest efficiency of 6.14%, outperforming those with P_M (5.08%) and P_L (4.29%).

The molecular orientation of a naphthalenediimide-bithiophene-based n-type polymer P(NDI2HD-T2) is effectively modulated by tuning the number average molecular weight (M_n). By increasing M_n values, the molecular orientation is shifted remarkably from edge-on to face-on with respect to the donor/acceptor interface and the electrodes. Thus, high M_n P(NDI2HD-T2) polymers produce enhanced charge generation and transport, resulting in highly efficient all-polymer solar cells.

Superior chemical sensing performance of black phosphorus (BP) is demonstrated by comparison with MoS₂ and graphene. Dynamic sensing measurements of multichannel detection show that BP displays highly sensitive, selective, and fast-responsive NO₂ sensing performance compared to the other representative 2D sensing materials.

Planar backbone, locked conformation, and low lowest unoccupied molecular orbital level provide polymer F₄BDOPV-2T with ultrahigh electron mobilities of up to 14.9 cm² V⁻¹ s⁻¹ and good air stability. It is found that the nonlinear transfer curves can be tuned to near-ideal ones by changing fabrication conditions, indicating that film morphology largely contributes to the nonlinear transfer curves in high-mobility conjugated polymers.

By creating an effective π-orbital hybridization between the fullerene cage and the aromatic anchor (addend), the azafulleroid interfacial modifiers exhibit enhanced electronic coupling to the underneath metal oxides. High power conversion efficiency of 10.3% can be achieved in organic solar cells using open-cage phenyl C₆₁ butyric acid methyl ester (PCBM)-modified zinc oxide layer.