High-performance large-area blade-coated perovskite solar cells with low ohmic loss for low lighting indoor applications

Emerging hybrid organic–inorganic perovskites with superior optoelectronic property demonstrate promising prospect for photovoltaic (PV) applications, in particular for low-lighting indoor applications e.g. within internet of things (IoT) networks or low-energy wireless communication devices. In order to prepare devices with high power output under low-illumination conditions, scalable fabrication techniques are preferred for large-area perovskite solar cells. In additions, one of the key parameters to achieve high-efficiency large-area perovskite solar cells is to minimize the ohmic loss to further boost the solar cell efficiency. Herein, a one-step blade-coating method assisted by hexafluorobenzene (HFB) was developed to deposit dense, large-area smooth and high- quality perovskite films with low ohmic loss. The as-fabricated devices demonstrated power conversion effi- ciency (PCE) of 20.7% (area of 0.2 cm2) and 16.5% (1 cm2), respectively, under standard (AM 1.5G) illumination conditions. Besides, the large-area (1 cm2) devices demonstrated a remarkable PCE of ~ 33.8% and ~ 30.0% under 1000 lx and 100 lx illumination provided by white light-emitting diode (LED) lamp, respectively. We exhibited a series-connected stack of large-area (totally active area ~ 4 cm2) perovskite photovoltaic device powering up a LED under common indoor environment as an indoor self-power indicator lamp. The analysis using a single diode model suggests that the high performance of the large-area devices under low-lighting in- door conditions is highly associated with the largely reduced ohmic losses, which particularly indicate that the perovskite films by a facile and scalable blade-coating method. The presented scalable approach paves the way to designing high-performance perovskite solar cells for a variety of emerging indoor PV application

High Shunt Resistance SnO2-PbO Electron Transport Layer for Perovskite Solar Cells Used in Low Lighting Applications

Hybrid perovskites are promising materials for new sustainable photovoltaic applications to operate under low lighting conditions, such as the reuse of residual photons that are wasted during indoor lighting. The requirements for a perovskite solar cell (PSC) to offer maximum power conversion efficiency (PCE) under low illumination conditions are not totally clear in the literature. In this work, the PCE of the commonly used SnO2 electron transport layer (ETL) is improved by a facile method, doping the precursor nanoparticles with small concentrations of a Pb source. Under low illumination conditions (i.e., 0.1 mW cm−2) the PCE is enhanced from 18.8% to 34.2%. From a complete analysis of the ETLs and devices using several structural and electrical techniques it is observed that the parameter that improves the most is the shunt resistance of the device which avoids the parallel leakage of the photogenerated current. The present work clearly shows that the shunt resistance is a very important parameter that needs to be optimized in PSCs for low illumination conditions.Funding for open access charge: CRUE-Universitat Jaume IThis work was supported by the Project on Collaborative Innovation and Environmental Construction Platform of Guangdong Province (No. 2018A050506067). The authors also thank the financial support from the Key Laboratory of Renewable Energy, Chinese Academy of Sciences (No. y807j71001), Guangdong Provincial Key Laboratory of New and Renewable Energy Research and Development (Grant No. Y909kp1001), and the Key Project on Synergy Collaborative Innovation of Guangzhou City (No. 201704030069). University Jaume I is also acknowledged for financial support (No. UJI-B2020-49)

The low temperature solution-processable SnO2 modified by Bi2O2S as an efficient electron transport layer for perovskite solar cells

Electron transport layer (ETL), promoting electron transportation and electron extraction, is an essential component of high efficiency perovskite solar cells (PVSCs). SnO2 has been proved to be an excellent ETL for efficient PVSCs due to its good optical transparency, high electrical conductivity, and suitable band position. In this work, we develop low temperature solution-processable SnO2 thin film modified by Bi2O2S nanoparticles as effective ETL of PVSCs for the first time. The results show the modification of the Bi2O2S nanoparticles can passivate oxygen vacancies of SnO2 thin film, resulting in less charge recombination and improved charge transport. Furthermore, SnO2 thin film modified by Bi2O2S nanoparticles enhances film morphology of overlying perovskite active layer, including larger grain size, better crystallinity. These eventually result in a remarkable improvement of performance of PVSCs. Compared to PVSCs with pristine SnO2 as ETL, the power conversion efficiency (PCE) of PVSCs with SnO2 modified by optimized Bi2O2S nanoparticles as ETL is raised to 17.13% from 14.61% with suppressed hysteresis. In addition, the modification of Bi2O2S can slightly enhance the stability of PVSCs due to reduced oxygen vacancies of SnO2 and better crystallinity of perovskite film. This work not only provides an effective mean of surface modification of SnO2, but also shows the Bi2O2S material has potential for applications for PVSCs. (C) 2019 Elsevier Ltd. All rights reserved

SnO2/2D-Bi2O2Se new hybrid electron transporting layer for efficient and stable perovskite solar cells

Interfacial engineering has been proved to be an effective way to enhance the performance of perovskite solar cells (PSCs) by reducing interfacial charge recombination. In this work, two-dimensional (2D) Bi2O2Se nano-flakes with high charge mobility are synthesized by facile composited molten salt method, and used as electron transport layer (ETL) of PSCs for the first time. The PSCs based on single 2D Bi2O2Se nanoflakes ETL exhibit power conversion efficiency (PCE) of 9.12%, which is 110% higher than those without ETL (4.32%). To fill pinholes and defects on the surface of SnO2 thin film, we also use the 2D Bi2O2Se nanoflakes to modify the surface of SnO2 thin film, and fabricate SnO2/2D-Bi2O2Se new hybrid ETL to effectively reduce recombination at hetero-interface. Owing to the high charge mobility of 2D Bi2O2Se nanoflakes and cascade band alignment between perovskite active layer and tin dioxide, more efficient electron transport in PSCs is obtained than the single SnO2 ETL. Moreover, novel hybrid ETL provides a smoother and more hydrophobic surface for larger perovskite crystal formation. Compared with PSCs with single SnO2 ETL, the PCE of PSCs based on SnO2/2D Bi2O2Se hybrid ETL is improved to 19.06% from 16.29% with suppressed hysteresis. More interesting, the stability of PSCs with the new hybrid ETLs is also improved due to the improved crystallinity of perovskite active layer. This work shows the 2D Bi2O2Se material has potential for applications in PSCs

Promising photovoltaic application of multi-walled carbon nanotubes in perovskites solar cells for retarding recombination

A facile spray deposition method was developed to prepare a high-quality perovskite layer under ambient conditions. However, the performance is expected to be further improved with substrate and the hole transport layer (HTL) optimization and device structure, for instance. MWCNTs with incorporated spiro-OMeTAD exhibited J(sc) of 22.13 mA cm(-2) and PCE of 10.42%. To infer the origin of the increasing J(sc) and PCE, the optical absorption performance, charge transfer and recombination performance were investigated tau, R-ct, R-rec as a function of voltage and EIS measurements revealed the lower transfer resistance and recombination rate in PSCs with MWCNTs compared with the PSCs without MWCNTs. The increased resistance in dark conditions and the dark J-V curves explain the slight changes in the V-oc. The SEM images showed that there were no MWCNTs aggregated on the surface of the spiro/MWCNTs composite layer and part of MWCNTs was uncovered by spiro-OMeTAD at the interface of HTM and Au electrode. The decreased I-D/I-G ratio from 0.90 to 0.68 demonstrated the increased interaction between MWCNTs and spiro-OMeTAD

Highly luminescent CsPbI3 quantum dots and their fast anion exchange at oil/water interface

In this paper, the highly emissive CsPbI3 perovskite quantum dots (QDs) with good stability are successfully synthesized with trioctylphosphine (TOP) as surface ligands. Furthermore, a facile and fast anion exchange is realized at the interface of nonpolar CsPbX3 solution and aqueous hydrohalic acid. Perovskite QDs can react with halide ions at room temperature swiftly to adjust their ratio of halogens and then the emission. The photo-luminescence (PL) can be tuned over wide spectral region (423.0-670.5 nm). And this work also provides a fast avenue to tune the emission of halide perovskite QDs

A facile method to improve the stability and efficiency of CsPbI2Br perovskite solar cells prepared at low temperature

CsPbI2Br has become the focus of researchers in recent years due to its excellent thermal stability compared to the organic-inorganic hybrid perovskites. However, it requires high temperature to form cubic phase, and it is difficult to maintain the cubic phase in the high humidity ambient. By adding 30 mu L levulinic acid (LA) to the CsPbI2Br precursor solution, cubic phase CsPbI2Br can be obtained by spin-coating three minutes (TMS) at room temperature (RT) instead of high temperature. Based on the TMS, highly quality cubic phase CsPbI2Br film can be obtained at 80 degrees C annealing temperature, the stability of cubic phase CsPbI2Br can be significantly improved by adding LA in the CsPbI2Br precursor solution. Based on this, CsPbI2Br cells without LA achieve 11.68% power conversion efficiency (PCE) at low temperature of 80 degrees C and the corresponding stabilized power output is 10.31%. Furthermore, 10 mu L LA addition CsPbI2Br cells keep its 50% PCE after 10 days under 35%RH and RT. This has found a new way to improve the stability of inorganic perovskite solar cells, and increasing its potential in flexible solar cells

Highly Solar-Reflective Litchis-Like Core-Shell HGM/TiO2 Microspheres Synthesized by Controllable Heterogeneous Precipitation Method

Hollow glass microsphere (HGM)TiO2 core-shell structural composites have promising applications in the field of energy efficient solar-reflective paints. In this work, after pretreated with saturated Ca(OH)(2) solutions, litchis-like TiO2 shells have been successfully synthesized on HGMs via a controllably heterogeneous precipitation method with Titanium (IV) sulfate (Ti(SO4)(2)) and urea as reaction precursors. It is emphasized that the use of urea as the precipitating agent is essential for the heterogeneous nucleation and growth of Ti(OH)(4) on HGMs, while the Ca(OH)(2) pretreatment provides the heterogeneous nucleation sites on HGMs which promotes the nucleation and growth of Ti(OH)(4), and gives rise to large secondary Ti(OH)(4) particles, leading to the formation of litchis-like TiO2 shells. The resulted core-shell structural HGM/TiO2 microspheres exhibited highest solar reflectance of similar to 83%

Stable Luminescent CsPbI3 Quantum Dots Passivated by (3-Aminopropyl)triethoxysilane

Perovskite nanomaterials have been fascinating for commercial applications and fundamental research owing to their excellent optical properties and satisfactory processability. They are expected to be alternative downconversion materials in phosphor-converted LEDs for lighting or display technology. However, owing to their low formation energy and large specific surface area, perovskite nanomaterials are sensitive to environmental stress like humidity, heat, etc. In this paper, cubic CsPbI3 quantum dots (QDs) with improved stability are synthesized using (3-aminopropyl)triethoxysilane (APTES). These luminescent CsPbI, QDs passivated by APTES not only show excellent stability when stored in hexane but also possess outstanding steadiness for lattice structure when prepared as a thin film in open air. They do not decompose immediately in the water. Such excellent stability is attributed to the hindrance from hydrolysis of APTES, which forms an analogous core-shell structure to protect the "core" CsPbI3 QDs. Furthermore, an additional iodine source is added to enhance their emissionm and CsPbI3 QDs with a PLQY of 84% are synthesized

One-step fabrication of copper sulfide catalysts for HER in natural seawater and their bifunctional properties in freshwater splitting

Natural seawater electrolysis is an efficient technology to produce hydrogen (H2) fuel and protects the environment from pollution. The lack of research on developing a suitable catalyst for hydrogen evolution reaction (HER) impedes generating an H2 sustainable fuel from natural seawater. In this study, copper sulfide (Cu2S) catalysts were successfully fabricated on nickel (Ni) foam with the help of a low-temperature hydrothermal technique by varying the growth temperatures in the range of 60-80 degrees C. The increase in growth temperatures improved the crystalline nature of the chalcocite Cu2S structure. The Cu2S catalyst fabricated at 80 degrees C showed a well-defined and improved the morphology with pores and small nanoparticles compared to other catalysts. An X-ray photoelectron spectroscope (XPS) showed the composition, oxidation state, and binding energy of the Cu2S catalysts. The Cu2S catalyst fabricated at 80 degrees C showed a little overpotential of 445 mV to attain 10 mA/cm2 for HER activity in natural seawater, and possessed higher intrinsic catalytic activity (136.10 mV/dec), electrochemical surface active site (634 cm2), and charge transfer properties (Rct, 4.40 ohm) with better long-term stability (86.7%) compared to other catalysts fabricated at 60 and 70 degrees C. Etching test of the Cu2S-80 degrees C catalyst in diluted hydrochloric (HCl) acid revealed no the insoluble precipitate on catalyst surface with a better 77.74% long-term stability. The bifunctional properties (HER and OER) of Cu2S catalysts for overall splitting were also investigated with three- and two-electrode cell configuration. The Cu2S catalyst fabricated at 80 degrees C exhibited a little overall cell potential of 1.65 V to reach 10 mA/cm2 compared to other Cu2S catalysts in 1 M KOH solution with impressive long-term stability of 99.23% up to 10 h. The Cu2S-80 degrees C catalyst was suitable for hydrogen production in natural seawater