The Effect of Energy Level of Transport Layer on the Performance of Ambient Air Prepared Perovskite Solar Cell: A SCAPS-1D Simulation Study

The perovskite solar cell (PSC) as an emerging and promising type has been extensively studied. In this study, a model for a PSC prepared in ambient air was established by using SCAPS-1D. After that, it was further analyzed through varying the defect density of the perovskite absorber layer (Nt), the thin film thickness and energy-level matching between the electron transport layer (ETL), the perovskite absorber layer and the hole transport layer (HTL), for a better understanding of the carrier features. The Nt varied from 1.000 × 1011 to 1.000 × 1017 cm−3. The performance of the solar cell is promoted with improved Nt. When Nt is at 1.000 × 1015 cm−3, the carrier diffusion length reaches μm, and the carrier lifetime comes to 200 nm. The thickness of the absorber layer was changed from 200 to 600 nm. It is shown that the absorber layer could be prepared thinner for reducing carrier recombination when at high Nt. The thickness effect of ETL and HTL is weakened, since Nt dominates the solar cell performance. The effect of the affinity of ETL (3.4–4.3 eV) and HTL (2.0–2.7 eV), together with three energy-level matching situations “ETL(4.2)+HTL(2.5)”, “ETL(4.0)+HTL(2.2)” and “ETL(4.0)+HTL(2.5)” on the performance of the solar cell were analyzed. It was found that the HTL with valence band 0.05 eV lower than that of the perovskite absorber layer could have a blocking effect that reduced carrier recombination. The effect of energy-level matching becomes more important with improved Nt. Energy-level matching between the ETL and perovskite absorber layer turns out counterbalance characteristic on Jsc and Voc, and the “ETL(4.0)+HTL(2.5)” case can result in solar cell with Jsc of 27.58 mA/cm2, Voc of 1.0713 V, FF of 66.02% and efficiency of 19.51%. The findings would be very useful for fabricating high-efficiency and low-cost PSC by a large-scale ambient air route.

Bi-doped Graphitic Carbon Nitride Nanotubes Boosts the Degradation Photocatalysis of Rhodamine B

Polymeric carbon nitride (PCN) is an emerging metal-free photocatalysts with high stability but is plagued by low photocatalytic efficiency due to the rapid charge carrier recombination behavior. Herein, Bi doped...

Physical and chemical aspects at the interface and in the bulk of CuInSe2-based thin-film photovoltaics

Technical issues which remain in CuInSe2-based solar cells are reviewed. A study of single-crystalline Cu(In,Ga)Se2 film devices, carrier recombination analysis, and effects of alkali-metal doping and silver-alloying are particularly focused on.

β-SnS/GaSe heterostructure: a promising solar-driven photocatalyst with low carrier recombination for overall water splitting

Various two-dimensional (2D) materials have been well investigated as promising high-efficiency photocatalysts for solar-driven water splitting, while the high carrier recombination greatly hinders their practical application. One effective route to...

Gas-Phase Fluorination of g-C3N4 for Enhanced Photocatalytic Hydrogen Evolution

Graphitic carbon nitride (g-C3N4) has attracted much attention because of its potential for application in solar energy conservation. However, the photocatalytic activity of g-C3N4 is limited by the rapidly photogenerated carrier recombination and insufficient solar adsorption. Herein, fluorinated g-C3N4 (F-g-CN) nanosheets are synthesized through the reaction with F2/N2 mixed gas directly. The structural characterizations and theoretical calculations reveal that fluorination introduces N vacancy defects, structural distortion and covalent C-F bonds in the interstitial space simultaneously, which lead to mesopore formation, vacancy generation and electronic structure modification. Therefore, the photocatalytic activity of F-g-CN for H2 evolution under visible irradiation is 11.6 times higher than that of pristine g-C3N4 because of the enlarged specific area, enhanced light harvesting and accelerated photogenerated charge separation after fluorination. These results show that direct treatment with F2 gas is a feasible and promising strategy for modulating the texture and configuration of g-C3N4-based semiconductors to drastically enhance the photocatalytic H2 evolution process.

Surface-Passivated CsPbBr3 for Developing Efficient and Stable Perovskite Photovoltaics

All-inorganic perovskites consisting of only inorganic elements have been recently considered as highly stable semiconductors for photoactive layer of optoelectronics applications. However, the formation of high-quality thin film and trap-reduced interface has still remains an important task, which should be solved for improving the performances of all-inorganic perovskite-based photovoltaics. Here, we adopted facile method that could reduce charge-carrier recombination by depositing a passivation agent on the top surface of the CsPbBr3 all-inorganic perovskite layer. We also found that the CsPbBr3 perovskite photovoltaic prepared from surface treatment method using n-octylammonium bromide provides an improved stability in ambient environment and 1-sun illuminating condition. Therefore, the perovskite photovoltaics fabricated from our approach offered an improved power conversion efficiency of 5.44% over that of the control device without surface treatment (4.12%).

The effect of net carriers at the interconnection layer in tandem organic solar cells

Tandem cell with structure of indium tin oxide (ITO)/ molybdenum oxide (MoO3)/ fullerene (C60) / copper phthalocyanine (CuPc)/ C60 / tris-8-hydroxy- quinolinato aluminum (Alq3)/Al was fabricated to study the effect of net carriers at the interconnection layer. The open circuit voltage and short circuit current were found to be 1.15 V and 0.56 mA/cm2, respectively. Almost the same performance (1.05 V, 0.58 mA/cm2) of tandem cell with additional recombination layer (ITO/MoO3/C60/Alq3/Al/Ag/MoO3/CuPc/C60/Alq3/Al) demonstrates that carrier balance is more crucial than carrier recombination. The net holes at the interconnection layer caused by more carrier generation from the back cell on one hand would enhance the recombination with electrons from the front cell and on the other hand would quench the excitons produced in CuPc of the back cell.

Rare earth doped metal oxide nanoparticles for photocatalysis: a perspective

Metal oxides are well-known materials that have been considered as the prominent photocatalysts. Photocatalysis is a promising way to address the environmental issues which arecaused by fossil fuel the combustion and industrial pollutants. Lots of efforts such as doping metal oxides with metals, non-metals or metals/non-metals have been made to enhance their photocatalytic activity. More specifically, in this review we have discussed detailed synthesis procedures of rare earth doped metal oxides performed in the past decades. The advantage of doping metal oxides with rare earth metals is that they readily combine with functional groups due to the 4f vacant orbitals. Moreover, doping rare earth metals causes absorbance shift to the visible region of the electromagnetic spectrum which results to show prominent photocatalysis in this region. The effect of rare earth doping on different parameters of metal oxides such as band gap and charge carrier recombination rate has been made in great details. In perspective section, we have given a brief description about how researchers can improve the photocatalytic efficiencies of different metal oxides in coming future. The strategies and outcomes outlined in this review are expected to stimulate the search for a whole new set of rare earth doped metal oxides for efficient photocatalytic applications.