Fabrication of a High-Quality Cu2ZnSn(S,Se)(4) Absorber Layer via an Aqueous Solution Process and Application in Solar Cells

The development of Cu2ZnSn(S,Se)(4) (CZTSSe) solar cells determines the prospect of thin-film photovoltaic devices because of some of their strengths. However, the usual solution fabrication processes of CZTSSe absorbing layers are either too tedious or highly toxic. Here, we have developed an alternative strategy to prepare kesterite CZTSSe absorber films with a simple and low-toxicity solution process by replacing the commonly employed thiol-based compounds using the glycolic acid aqueous solution, which significantly reduces the environment pollution and toxicity, providing a possibility toward the green solvent process. The power conversion efficiency of 6.81% has been acquired based the aqueous solution-processed CZTSSe thin film via optimizing the fabrication technology

A review on the stability of inorganic metal halide perovskites : challenges and opportunities for stable solar cells

Inorganic perovskite based solar cells (PSCs) have been receiving unprecedented attention worldwide in the past several years due to their higher intrinsic stability towards high temperatures and high theoretical power conversion efficiencies. Since a photovoltaic performance of 20.37% has been achieved for inorganic PSCs recently, the operational stability of these devices has become the major bottleneck which impedes their commercialization. The high thermal stability associated with inorganic perovskites comes along with poorer phase stability compared to their hybrid counterparts and therefore needs thorough understanding. Lattice strain and vacancies within the perovskite crystals are found to be the origin of these phase instability issues. This review summarizes the progress in stability research on inorganic perovskites. Specifically, the degradation mechanisms of inorganic perovskites towards temperature, moisture and oxygen are summarized and discussed. Solutions for tackling these stability issues are reviewed and an outlook on further strategies is provided

H-2-Ar dilution for improved c-Si quantum dots in P-doped SiNx:H thin film matrix

Phosphorus-doped hydrogenated silicon nitride (SiNx:H) thin films containing crystalline silicon quantum dot (c-Si QD) was prepared by plasma enhanced chemical vapor deposition (PECVD) using hydrogen-argon mixed dilution. The effects of H-2/Ar flow ratio on the structural, electrical and optical characteristics of as-grown P-doped SiNx:H thin films were systematically investigated. Experimental results show that crystallization is promoted by increasing the H-2/Ar flow ratio in dilution, while the N/Si atomic ratio is higher for thin film deposited with argon-rich dilution. As the H-2/Ar flow ratio varies from 100/100 to 200/0, the samples exhibit excellent conductivity owing to the large volume fraction of c-Si QDs and effective P-doping. By adjusting the H-2/Ar ratio to 100/100, P-doped SiNx:H thin film containing tiny and densely distributed c-Si QDs can be obtained. It simultaneously possesses wide optical band gap and high dark conductivity. Finally, detailed discussion has been made to analyze the influence of H-2-Ar mixed dilution on the properties of P-doped SiNx:H thin films. (C) 2016 Elsevier B.V. All rights reserved

Carbonyl Linked Carbon Nitride Loading Few Layered MoS2 for Boosting Photocatalytic Hydrogen Generation

Pristine graphitic carbon nitride g-C3N4 materials, as a novel metal-free photocatalyst with moderate activity, have attracted intense interest. However, its fast photogenerated carriers recombination always induces a relative low performance. Herein, we for the first time report one new =C=O group linked g-C3N4 (CO-C3N4) through CO2-assisted thermal polymerization of urea. It is found that the edge =C=O groups work as the photogenerated electrons collection sites and then promote the carriers separation. The visible-light photo-tatalytic hydrogen evolution performance of our synthesized samples shows 1.85 times higher than that of the reference g-C3N4. To get a considerable visible-light driven photocatalytic hydrogen generation, a new few layered MoS2 with a small size (ca. 20 nm) is prepared through a liquid exfoliation and then is loaded onto the CO-C3N4. The optimal MoS2/CO-C3N4 sample gives the photocatalytic hydrogen evolution of 1990 and 1440 mu mol/(g*h) under the lambda > 400 and 420 illumination, higher than the reported values in the literature. The sample also shows a considerable excellent photocatalytic activity of 44.3 mu mol/(g*h) under LED-600 condition

Monolayer-by-monolayer growth of platinum films on complex carbon fiber paper structure

A controlled monolayer-by-monolayer deposition process has been developed to fabricate Pt coating on carbon fiber paper with complex network structures using a dual buffer (Au/Ni) strategy. The X-ray diffraction, electrochemical quartz crystal microbalance, current density analyses, and X-ray photoelectron spectroscopy results conclude that the monolayer deposition process accomplishes full coverage on the substrate and that the thickness of the deposition layer can be controlled on a single atom scale. This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. In fact, the present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value. (C) 2017 Elsevier B.V. All rights reserved

Interfaces and interfacial layers in inorganic perovskite solar cells

Owing to their superior thermal stability, metal halide inorganic perovskite materials continue to attract interest for photovoltaics applications. The highest reported power conversion efficiency (PCE) for solar cells based on inorganic perovskites is over 20 %. As this PCE corresponds to 73 % of the theoretical limit, there remains more room for further improving the device PCEs than for improving organic–inorganic hybrid perovskite solar cells (PSCs). The main loss is in the photovoltage, which is limited by interfaces in terms of non-radiative recombination caused by traps and energy-level mismatch. Furthermore, inefficient charge extraction at interfacial contacts reduces the photocurrent and fill factor. This Minireview summarizes the recent developments in the fundamental understanding of how the interfaces and interfacial layers influence the performance of solar cells based on inorganic perovskite absorbers. An outlook for the development of highly efficient and stable inorganic PSCs from the interface point of view is also given

Recent Progress in Single-Crystalline Perovskite Research Including Crystal Preparation, Property Evaluation, and Applications

Organic-inorganic lead halide perovskites are promising optoelectronic materials resulting from their significant light absorption properties and unique long carrier dynamics, such as a long carrier lifetime, carrier diffusion length, and high carrier mobility. These advantageous properties have allowed for the utilization of lead halide perovskite materials in solar cells, LEDs, photodetectors, lasers, etc. To further explore their potential, intrinsic properties should be thoroughly investigated. Single crystals with few defects are the best candidates to disclose a variety of interesting and important properties of these materials, ultimately, showing the increased importance of single-crystalline perovskite research. In this review, recent progress on the crystallization, investigation, and primary device applications of single-crystalline perovskites are summarized and analyzed. Further improvements in device design and preparation are also discussed

Kesterite Cu2Zn(Sn,Ge)(S,Se)(4) thin film with controlled Ge-doping for photovoltaic application

Cu2ZnSn(S,Se)(4) (CZTSSe) semiconductors have been a focus of extensive research effort owing to low-toxicity, high abundance and low material cost. Yet, the CZTSSe thin film solar cell has a low open-circuit voltage value that presents challenges. Herein, using GeSe2 as a new Ge source material, we have achieved a wider band gap CZTSSe-based semiconductor absorber layer with its band-gap controlled by adjusting the ratio of SnS2 : GeSe2 used. In addition, the Cu2Zn(Sn,Ge)(S,Se)(4) thin films were prepared with optimal Ge doping (30%) and solar cells were fabricated to attain a respectable power conversion efficiency of 4.8% under 1.5 AM with an active area of 0.19 cm(2) without an anti-reflection layer

Origin of enhanced stability in thiocyanate substituted -FAPbI(3) analogues

In the past few years, hybrid perovskites have emerged as the most promising photovoltaic materials due to their excellent optoelectronic properties, and easy fabrication methods. However, the long-term stability is still the main obstacle for their commercial applications. Recently, thiocyanate-doped hybrid perovskites have shown enhanced stability and impressive efficiency, but the reason is still unknown. Herein, we discussed the enhanced stability of SCN-substituted pseudocubic FABX(3) (B=Pb2+, Sn-2+; X=I-, Br-, and Cl-) based on the density functional theory. Through a series of calculations of Bader charge transfer, vacancy formation energies of different kinds of vacancies, decomposition enthalpy, phonon density of states, and ab initio molecular dynamics simulation, we conclude that the incorporation of SCN- can stabilize pseudocubic FABX(3), and attribute the enhanced stability mainly to two factors: (1) the strong interaction between Pb2+/Sn2+ and SCN-, as well as the strong hydrogen bonding between FA(+) and X-/SCN-, and (2) the structural tilting induced by the incorporation of SCN-. These findings provide alternative method fortuning the poor stability of pseudocubic FABX(3), as well as for obtaining high-performance solar cells

Effective light trapping by hybrid nanostructure for crystalline silicon solar cells

Ag nanoparticles (NPs), as etching catalyst,. are applied onto the pyramid textured surface of the semi-finished single crystalline silicon solar cell by spraying a solution containing AgNO3 and sodium citrate. Upon chemical etching, nanopits are formed with the Ag NPs staying inside of the nanopits. Complete solar cells with and without the Ag-assisted etching are fabricated to study the effects of the hybrid nanostructure. It is found that the optical reflection is effectively reduced by the nanostructure and the incident light is harvested more effectively for enhanced external quantum efficiency (EQE) by as much as 17% for the cells before the SiNx anti-reflection coating, and the EQE can be further enhanced by applying an electric bias 1 V during the EQE measurement. It is believed that when the solar cell with the Ag NPs is illuminated, the local surface plasmon resonance (LSPR) is induced at the specific wavelength regions around 405 and 810 nm. For ultraviolet light, the LSPR effect dominates the increases of the EQE while the effective medium effect is also believed to be responsible for the effective light trapping. (C) 2015 Elsevier B.V. All rights reserved