ZiQi Sun

A novel low-cost aluminum–graphite dual-ion battery is reported. The battery shows a reversible capacity of ≈100 mAh g⁻¹ and a capacity retention of 88% after 200 charge–discharge cycles. A packaged aluminum–graphite battery is estimated to deliver an energy density of ≈150 Wh kg⁻¹ at a power density of ≈1200 W kg⁻¹, which is ≈50% higher than most commercial lithium ion batteries.

The degradation of sexithiophene cascade organic solar cells is studied. Glass–glass encapsulated devices on indium tin oxide as transparent electrode show efficiencies of 6.6% and degrade within 500 h in illuminated 38 °C/50% RH climate. Fully flexible devices with silver nanowire electrode and alumina barrier achieve 5% efficiency and degrade within 30 h due to electrode failure.

An approach to fabricate high-efficiency inverted planar perovskites solar cells using solution-processed organic small molecules hole transporting layer is reported. Devices using CH₃NH₃PbI₃ as photoactive layer and PC₆₀BM as electron transport layer show power conversion efficiencies exceeding 12% and open-circuit voltages (V_OC) higher than 1 V.

The influence of monovalent cation halide additives on the optical, excitonic, and electrical properties of CH₃NH₃PbI₃ perovskite is reported. Monovalent cation halide with similar ionic radii to Pb²⁺, including Cu⁺, Na⁺, and Ag⁺, have been added to explore the possibility of doping. Significant reduction of sub-bandgap optical absorption and lower energetic disorder along with a shift in the Fermi level of the perovskite in the presence of these cations has been observed. The bulk hole mobility of the additive-based perovskites as estimated using the space charge limited current method exhibits an increase of up to an order of magnitude compared to the pristine perovskites with a significant decrease in the activation energy. Consequentially, enhancement in the photovoltaic parameters of additive-based solar cells is achieved. An increase in open circuit voltage for AgI (≈1.02 vs 0.95 V for the pristine) and photocurrent density for NaI- and CuBr-based solar cells (≈23 vs 21 mA cm⁻² for the pristine) has been observed. This enhanced photovoltaic performance can be attributed to the formation of uniform and continuous perovskite film, better conversion, and loading of perovskite, as well as the enhancement in the bulk charge transport along with a minimization of disorder, pointing towards possible surface passivation.

Incorporation of monovalent cation halide additives improve the semiconductor behavior and photovoltaic performance of CH₃NH₃PbI₃ perovskite through the formation of uniform and continuous perovskite film, better conversion and loading of CH₃NH₃PbI_3, and possible passivation of defect states at the crystallite surfaces, as well as the enhancement in the bulk charge transport along with a minimization of disorder.

High-quality perovskite monocrystalline films are successfully grown through cavitation-triggered asymmetric crystallization. These films enable a simple cell structure, ITO/CH₃NH₃PbBr₃/Au, with near 100% internal quantum efficiency, promising power conversion efficiencies (PCEs) >5%, and superior stability for prototype cells. Furthermore, the monocrystalline devices using a hole-transporter-free structure yield PCEs ≈6.5%, the highest among other similar-structured CH₃NH₃PbBr₃ solar cells to date.

NiO is a promising hole transporting material for perovskite solar cells due to its high hole mobility, good stability, easy processibility, and suitable Fermi level for hole extraction. However, the efficiency of NiO-based cells is still limited by the slow hole extraction due to the poor perovskite/NiO interface and the inadequate quality of the two solution-processed material phases. Here, large influences of a monolayer surface modification of NiO nanocrystal layers with ethanolamine molecules are demonstrated on the enhancement of hole extraction/transport and thus the photovoltaic performance. The underlying causes have been revealed by a series of studies, pointing to a favorable dipole layer formed by the molecular adsorption along with the enhanced perovskite crystallization and the improved interface contact. Comparatively, the solar cells based on a diethanolamine-modified NiO layer have achieved a rather high fill factor, indeed one of the highest among NiO-based perovskite solar cells, and high short-circuit photocurrent density (J_sc), resulting in a power conversion efficiency of ≈16%, most importantly, without hysteresis.

Diethanolamine (DEA) modification of the thin NiO film surface in perovskite solar cells enhances the interfacial hole extraction rate and thus the photovoltaic performance. Perovskite film quality and the contact at the perovskite/NiO interface are greatly improved through the chemical coordination of Ni and Pb with the –NH– and –OH groups of DEA, respectively.

The Al₂O₃ passivation layer is beneficial for mesoporous TiO₂-based perovskite solar cells when it is deposited selectively on the compact TiO₂ surface. Such a passivation layer suppressing surface recombination can be formed by thermal decomposition of the perovskite layer during post-annealing.

The successful application of a Ni/Au transparent electrode for fabricating efficient perovskite-based solar cells is demonstrated. Through interdiffusion of the Ni/Au bilayer, Au forms an interconnected metallic network structure as the transparent electrode. Ni diffuses to the bilayer surface and oxidizes into NiO_x becoming an appropriate electrode interlayer. These ITO- and PEDOT:PSS-free devices have potential applications in the design of future cost-effective, low-weight, and stable solar cells.

Graphene, the thinnest, strongest, and stiffest material with exceptional thermal conductivity and electron mobility, has increasingly received world-wide attention in the past few years. These unique properties may lead to novel or improved technologies to address the pressing global challenges in many applications including transparent conducting electrodes, field effect transistors, flexible touch screen, single-molecule gas detection, desalination, DNA sequencing, osmotic energy production, etc. To realize these applications, it is necessary to transfer graphene films from growth substrate to target substrate with large-area, clean, and low defect surface, which are crucial to the performances of large-area graphene devices. This critical review assesses the recent development in transferring large-area graphene grown on Fe, Ru, Co, Ir, Ni, Pt, Au, Cu, and some nonmetal substrates by using various synthesized methods. Among them, the transfers of the most attention kinds of graphene synthesized on Cu and SiC substrates are discussed emphatically. The advances and the main challenges of each wet and dry transfer method for obtaining the transferred graphene film with large-area, clean, and low defect surface are also reviewed. Finally, the article concludes the most promising methods and the further prospects of graphene transfer.

Graphene has increasingly received world-wide attention in the past few years. It is necessary to transfer graphene films from growth substrate to target substrate when fabricating graphene-based devices. This critical review assesses the recent development in transferring large-area graphene and concludes the most promising methods and the further prospects of graphene transfer.

Self-doped and crown-ether functionalized fullerene PCMI:K⁺ works well as a cathode buffer layer in polymer solar cells based on PTB7-Th, with a power conversion efficiency (PCE) of 10.30%, which is one of the highest PCEs to date. A series of experiments are used to shed light upon the mechanism of the simultaneous elevation in photovoltaic parameters with PCMI:K⁺.

This work proposes a new perovskite solar cell structure by including lithium-neutralized graphene oxide (GO-Li) as the electron transporting layer (ETL) on top of the mesoporous TiO₂ (m-TiO₂) substrate. The modified work-function of GO after the intercalation of Li atoms (4.3 eV) exhibits a good energy matching with the TiO₂ conduction band, leading to a significant enhancement of the electron injection from the perovskite to the m-TiO₂. The resulting devices exhibit an improved short circuit current and fill factor and a reduced hysteresis. Furthermore, the GO-Li ETL partially passivates the oxygen vacancies/defects of m-TiO₂ by resulting in an enhanced stability under prolonged 1 SUN irradiation.

Lithium-neutralized graphene oxide (GO-Li) as electron transporting layer in perovskite solar cells is reported. The proposed device conjugates the extraordinary conduction properties of graphene based materials with the exceptional harvesting behavior of organoleadtrihalide compounds and shows enhanced power conversion efficiency and improved long term stability under operative conditions.