Enhanced Power Conversion Efficiency Research Articles

Suppressed Degradation and Enhanced Performance of CsPbI3 Perovskite Quantum Dot Solar Cells via Engineering of Electron Transport Layers.

CsPbI3 perovskite quantum dots (CsPbI3-PQDs) have recently come into focus as a light-harvesting material that can act as a platform through which to combine the material advantages of both perovskites and QDs. However, the low cubic-phase stability of CsPbI3-PQDs in ambient conditions has been recognized as a factor that inhibits device stability. TiO2 nanoparticles are the most regularly used materials as an electron transport layer (ETL) in CsPbI3-PQD photovoltaics; however, we found that TiO2 can facilitate the cubic-phase degradation of CsPbI3-PQDs due to its vigorous photocatalytic activity. To address these issues, we have developed chloride-passivated SnO2 QDs (Cl@SnO2 QDs), which have low photocatalytic activity and few surface traps, to suppress the cubic-phase degradation of CsPbI3-PQDs. Given these advantages, the CsPbI3-PQD solar cells based on Cl@SnO2 ETLs show significantly improved device operational stability (under conditions of 50% relative humidity and 1-sun illumination), compared to those based on TiO2 ETLs. In addition, the Cl@SnO2-based devices showed improved open circuit voltage and photocurrent density, resulting in enhanced power conversion efficiency (PCE) up to 14.5% compared to that of TiO2-based control devices (PCE of 13.8%).

Plasmonic silver sandwich structured photoanode and reflective counter electrode enhancing power conversion efficiency of dye-sensitized solar cell

This work describes the efficient improvement of dye-sensitized solar cells (DSSC) utilizing a photoanode with a plasmonic sandwiched silicon dioxide/silver/titanium dioxide (SiO2/Ag/TiO2) structure and a counter electrode (CE) of polypyrrole/reduced graphene oxide/indium tin oxide (Ppy/rGO/ITO) assembled with an aluminium (Al) foil as a reflective layer. The localized surface plasmonic resonance induced from Ag increases the absorption of the dye molecules, and hence significantly improves the electron collection and light-harvesting efficiencies. Compared with conventional photoanode of DCCSs composed of TiO2 paste, the photovoltaic cells containing the plasmonic sandwiched structure exhibits a remarkable improvement in the power conversion efficiency (ƞ), with up to a 2-fold enhancement (from 0.6% to 1.2%), along with a 68.37% increment in the short-circuit current density (Jsc), from 2.15 to 3.62 mA cm−2. The reflective layer of Al foil contributes to a significant enhancement of ƞ of 1.7-fold for the DSSC.

Efficiency enhancement of low-cost metal free dye sensitized solar cells via non-thermal atmospheric pressure plasma surface treatment

Dye sensitized solar cells (DSSC) are an attractive third-generation photovoltaic technology particularly promising for operation under diffuse and lower light conditions. However, high costs of the precious metals used for sensitizing dyes and low charge generation capability parameters limit the utility of DSSCs in comparison to conventional silicon solar cells. In this study, tin oxide (SnO2) photoelectrodes are treated with non-thermal atmospheric pressure plasmas to enhance photovoltaic performance. The effects of nitrogen and argon plasma surface treatment of photoanodes on the efficiency enhancement of DSSCs are systematically investigated by fabricating solar cells using pristine SnO2 and plasma-treated photoanodes. Solar cells made with Eosin Y sensitized pristine SnO2 photoanode exhibited a short circuit current density (JSC) of 1.03 mA cm−2 and an overall power conversion efficiency (PCE) of 0.30% whereas solar cells made with nitrogen plasma treated photoanode exhibited a JSC of 6.20 mA cm−2 and an overall PCE of 1.53% (4 times enhancement) under the same illumination of 100 mW cm−2 (AM 1.5). The efficiency of the solar cells fabricated with Ar plasma treated SnO2 photoanodes also showed an enhanced power conversion efficiency. Further characterizations revealed that the surface plasma treatments increased the surface roughness of the photoanodes. Plasma treatment led to the incorporation of nitrogen species and removal of surface impurities resulting in an increase in dye adsorption in the photoanode and hence the enhancement in the efficiency of the DSSC. This study demonstrated a one-pot treatment method for efficiency enhancement which could be used in various applications such as photovoltaic, catalytic and energy generation applications including DSSCs, thin-film solar cells, perovskite solar cells, gas sensing, bio-sensing, supercapacitors, Li-ion batteries and others.

Boosting power conversion efficiency by hybrid triboelectric nanogenerator/silicon tandem solar cell toward rain energy harvesting

The weather-dependence and intermittent photoelectric conversion capacity of the traditional photovoltaics call for rational design on device architecture to realize persistent power output under multiple-energy-source stimuli. Herein, we demonstrate a novel triboelectric nanogenerator/silicon (TENG/Si) tandem hybrid solar cell by stacking top silver/polydimethylsiloxane sub-cell onto bottom monocrystalline Si solar cell for simultaneously harvesting solar and rain energies. Upon systematically optimizing the device configuration and the properties of top nanogenerator, the bottom Si solar cell is used as a friction layer to regulate the charge distribution of TENG, achieving a short-circuit current of 7.59 μA, a peak open-circuit voltage of 37.19 V under the stimuli of single raindrop and a power conversion efficiency enhancement by 20% in comparison with pristine Si solar cell. Finally, 26 blue light-emitting diodes can be lighted up by one raindrop. Given the compelling advantages of enhanced power output and expanded working time, this physical proof-of-concept TENG/Si tandem hybrid solar cell provides new opportunities to collect multiple energies from nature and to promote the development of weather-independent solar cells.

Energy harvesting textiles: using wearable luminescent solar concentrators to improve the efficiency of fiber solar cells

The integration of fiber solar cells (FSCs) and wearable luminescent solar concentrators leads to an enhancement of power conversion efficiency of FSCs.

Surface passivation of organometal halide perovskites by atomic layer deposition: an investigation of the mechanism of efficient inverted planar solar cells.

Interface passivation plays a pivotal role in achieving high-efficiency organic metal halide perovskite solar cells (PSCs). It has been recently revealed that atomic layer deposition (ALD) of wide-band gap oxides shows great potential to effectively passivate defects at the interface, and ALD is also of great technological promise for industrial upscaling. However, the conflicting observations of ALD passivation are often reported in the literature, even with very similar ALD conditions. To unveil the involved crucial mechanism, this work carefully investigates the evolution of a representative MAPbI3 perovskite surface during the ALD of Al2O3, by employing the technique of in situ X-ray photoelectron spectroscopy. The ALD at 125 °C was found to cause significant degradation of the perovskite; lowering the deposition temperature can largely minimize the degradation, and 75 °C was found to be the best ALD temperature. Following this conclusion, inverted planar perovskite solar cells were prepared in ambient conditions with ALD Al2O3 interlayers. Indeed, cells with the interlayer deposited at 75 °C exhibited a significantly enhanced power conversion efficiency from 18.8% (champion 19.2%) to 20.0% (champion 20.4%). Photoluminescence measurements further evidence that the ALD layer can effectively passivate defect states at the perovskite surface. Considering the great representativeness and broad applicability of MAPbI3 and ALD Al2O3, the mechanism and strategy reported herein should be of significant value for the perovskite interface engineering in general.

Investigation on Open-Circuit Voltage of an Efficiency-Boosting Solar Cell Technique Featuring V-Configuration

The V-Shaped Module (VSM) solar cell technology, which breaks the traditional concept of solar cell system, has been proven to enhance power conversion efficiency of some solar cells and has offered opportunities to increase generation power densities in area-limited applications. Compared to a planar cell system, the VSM has an additional opportunity to absorb photons and taps the potential of solar cells. In this study, the VSM, the proposed common technique enhancing efficiencies of various solar cells, was investigated by using commercially available multi-crystalline silicon solar cells. The VSM technique enables the efficiencies of the multi-crystalline silicon cells to increase from 13.4% to 20.2%, giving an efficiency boost of 51%. Though the efficiency of the cells increases, the open-circuit voltage of the cells decreases owing to the VSM technique. Furthermore, the obvious reduction in open-circuit voltage in the VSM was found and the phenomenon is explained for the first time.

Anchored porphyrin with different side chain groups via its axial coordinate self-assembly for dye-sensitized solar cells

In this work, four anchored zinc porphyrins ZnPAi (i = 1–4) with different side chain substituent groups and antenna porphyrin ZnP1 have been designed, synthesized, and characterized. Anchored porphyrin ZnPAi (i = 1–4) and its self-assemblies formed by axial coordination with antenna porphyrin have been used as sensitizers in dye-sensitized solar cells. Our results indicate that cells based on self-assemblies exhibited obviously enhanced power conversion efficiency. In particular, the solar cells based on the zinc porphyrin (ZnPA2) with t-butyl side chain groups show higher conversion efficiency than that of other side chain porphyrin based devices. These results were also verified by optical performance, photocurrent conversion efficiency, and electrochemical impedance spectroscopy. In addition, the energy level and ground state geometric configuration of the dye were calculated, and the ultraviolet-visible absorption spectrum was simulated through density functional theory to further verify its photoelectric behavior.

Enhanced Performance of Dye-Sensitized Solar Cells Via the Synergic Effect of Hierarchical TiO2 Networks and Au Nanoparticle Decoration

The construction of favorable photoanode configurations is of great importance to enhance the performance of dye-sensitized solar cells (DSSCs). In this work, a double-layer photoanode architecture consisting of a top layer of hierarchical TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> networks (HTNs) and a bottom layer of commercial P25 nanoparticles (NPs) was designed and prepared by a facile one-step hydrothermal method. This unique double-layer structure not only affords stronger light scattering and faster electron transport relative to the single-layer P25 photoanode, but also ensures more close contact between different functional layers in contrast to commonly used multistep mechanical coated photoanodes. Furthermore, Au NPs with particle sizes of around 20 nm were incorporated to decorate the HTN photoanode. The localized surface plasmon resonance effect of such Au NPs significantly enhances the light absorption of N719 dye molecules. Benefitted from the splendid light harvesting and superior electron collection, the Au-HTN photoanode configuration delivers an enhanced power conversion efficiency of 5.97%, yielding ~19% improvement compared to the device based on the conventional P25 photoanode. This work highlights the design of photoanodes with unique nanostructures for enhancing the photovoltaic performance of DSSCs.

Dual Defect-Passivation Using Phthalocyanine for Enhanced Efficiency and Stability of Perovskite Solar Cells.

Semiconducting molecules have been employed to passivate traps extant in the perovskite film for enhancement of perovskite solar cells (PSCs) efficiency and stability. A molecular design strategy to passivate the defects both on the surface and interior of the CH3 NH3 PbI3 perovskite layer, using two phthalocyanine (Pc) molecules (NP-SC6 -ZnPc and NP-SC6 -TiOPc) is demonstrated. The presence of lone electron pairs on S, N, and O atoms of the Pc molecular structures provides the opportunity for Lewis acid-base interactions with under-coordinated Pb2+ sites, leading to efficient defect passivation of the perovskite layer. The tendency of both NP-SC6 -ZnPc and NP-SC6 -TiOPc to relax on the PbI2 terminated surface of the perovskite layer is also studied using density functional theory (DFT) calculations. The morphology of the perovskite layer is improved due to employing the Pc passivation strategy, resulting in high-quality thin films with a dense and compact structure and lower surface roughness. Using NP-SC6 -ZnPc and NP-SC6 -TiOPc as passivating agents, it is observed considerably enhanced power conversion efficiencies (PCEs), from 17.67% for the PSCs based on the pristine perovskite film to 19.39% for NP-SC6 -TiOPc passivated devices. Moreover, PSCs fabricated based on the Pc passivation method present a remarkable stability under conditions of high moisture and temperature levels.

Effects of Fluorination on Fused Ring Electron Acceptor for Active Layer Morphology, Exciton Dissociation, and Charge Recombination in Organic Solar Cells.

Fluorination is one of the effective approaches to alter the organic semiconductor properties that impact the performance of the organic solar cells (OSCs). Positive effects of fluorination are also revealed in the application of fused ring electron acceptors (FREAs). However, in comparison with the efforts allocated to the material designs and power conversion efficiency enhancement, understanding on the excitons and charge carriers' behaviors in high-performing OSCs containing FREAs is limited. Herein, the impact of fluorine substituents on the active layer morphology, and therefore exciton dissociation, charge separation, and charge carriers' recombination processes are examined by fabricating OSCs with PTO2 as the donor and two FREAs, O-IDTT-IC and its fluorinated analogue O-IDTT-4FIC, as the acceptors. With the presence of O-IDTT-4FIC in the devices, it is found that the excitons dissociate more efficiently, and the activation energy required to split the excitons to free charge carriers is much lower; the charge carriers live longer and suffer less extent of trap-assisted recombination; the trap density is 1 order of magnitude lower than that of the nonfluorinated counterpart. Overall, these findings provide information about the complex impacts of FREA fluorination on efficiently performed OSCs.

Efficiency enhancement in planar perovskite solar cells under low-light illumination and ambient lighting

Hybrid organic-inorganic perovskite solar cells (PSCs) have attracted significant interest owing to their high power conversion efficiency (PCE) and low cost. Moreover, PSCs demonstrate high performance under low light illumination without significant reduction in PCE. However, photovoltaic properties of PSCs under low light conditions are rarely reported. Here, the potential of planar PSCs for efficient performance under low illuminance conditions was investigated. Planar perovskite solar cells with FTO/c-TiO2/c-SnO2/CH3NH3PbI3/Spiro-MeOTAD/Au architecture were studied under variable illumination intensities in the range of 10 – 1000 W/m2. Significant enhancement in PCE up to 18.4% was observed for planar PSCs under low light conditions (<100 W/m2), as compared to the 16% PCE value obtained under AM1.5 illumination. This was attributed to the decreased charge accumulation at the ETL/perovskite interface and increased charge collection efficiency under low light illumination. PSCs performance was additionally studied under artificial LED lighting (5500K, 1000 lux) and the PCE values exceeding 24% were obtained. The results of this work verify excellent low-light performance of planar PSCs and provide the possibility for their application as power sources for various low-power wireless devices (sensors, detectors, Internet of Things devices, etc.).

Hybrid Hole Extraction Layer Enabled High Efficiency in Polymer Solar Cells.

Charge extraction layers with excellent charge extraction capability are essential for achieving high photovoltaic performance in cells. In this work, a hole extraction layer (HEL) is developed by doping conductive polymer TFB into CuSCN (CuSCN:TFB(X)), which exhibits good light transparency and high affinity for the light absorber. Compared to the reference cell, the CuSCN:TFB(X) HEL-based cells show impressive enhancement owing to the increased exciton dissociation and charge extraction processes and weak recombination losses. Furthermore, matched work function, better interface contact, and appropriate domain size also contribute to the enhanced power conversion efficiency. As a consequence, the highest conversion efficiency of 15.28% is observed in a cell based on the PM6:Y6 blend film and CuSCN:TFB(1.0%) HEL, which is >16% higher than the efficiency of 13.13% in a cell with CuSCN HEL.

Assembly of Fe(III)‐Grafted Metal–Organic Complexes as p‐Type Dopants for Efficient and Stable Perovskite Solar Cells

Realizing the rapid/controllable oxidation of 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (Spiro‐OMeTAD) under an inert atmosphere, reducing the J–V hysteresis and enhancing the air stability of devices is extremely significant to fabricate high‐performance perovskite solar cells (PSCs). Herein, the Fe(III) ion grafted metal–organic complexes (Fe(III) ⊂ MOCs) are assembled and used as the p‐type dopants of hole transport layers (HTLs) to prepare efficient and stable PSCs. Consequently, the optimal Fe(III) ⊂ In‐2‐bpydc‐doped device presents a significantly enhanced power conversion efficiency (PCE) of 20.46%, benefitting from the improved hole extraction and weakened carrier recombination at the interface between HTLs and perovskite films. More importantly, the modified device possesses a reduced J–V hysteresis index (HI) of 0.094, and can maintain nearly 90% of its initial PCE value after being exposed to the air at ≈25 °C and relative humidity (RH) of ≈35% for 4 weeks, which is attributed to the restrained detrimental penetration behavior by the MOC carrier part of dopants. This work is of important guiding significance for the application of MOC materials in photovoltaic fields.

Effect of SrF2:Pr3+-Yb3+ Nanophosphor on Downconversion of High Energy Photons for Efficient Dye-Sensitized Solar Cells

An emerging important class of photovoltaics for the next generation, the dye sensitized solar cells (DSSCs) has attracted great attention due to its low-cost, simple fabrication process and good performance. Though, one of the major loss mechanisms leads to lowering the power energy conversion efficiency is thermalization of charge carriers generated by the absorption of high energy photons. One promising novel strategy to decrease such thermalization loss is the use of downconversion (DC) luminescent materials as spectral converters. The rare-earth doped downshifting materials can converts higher energy photons into lower energy photons based on energy transfer from lanthanide ions to Yb3+ ions. In addition, the downconversion nanoparticles (DCNPs) are also act as scattering centers which can facilitates the light capture in photo-absorbing layer. With this aim, the rare earth doped downconversion SrF2: Pr3+-Yb3+ nanoparticles were synthesized by facile template free hydrothermal method. X-ray diffraction analysis confirms the formation cubic SrF2 phase. The prepared SrF2: Pr3+-Yb3+ down-shifting nanophosphor shows strong absorption in UV region and broad luminescence band emission in visible region evidenced from absorption and photoluminescence studies respectively. The enhancement in power conversion efficiency (PCE) was achieved by employing the synthesized downconverting nanomaterial as bottom layer in DSSC photoanode (Fig.1). The photovoltaic performance of the device was studied using standard solar simulator at 1 Sun intensity (AM 1.5 G) and DSSC with SrF2: Pr3+-Yb3+ shows improved efficiency of 9.066% than bare TiO2 based device (8.395%). The down-shifting nanophosphor material enhanced the efficiency of DSSC by 7.4% with 7.5% increment in photocurrent density compared to bare TiO2 based device. Figure 1

Donor–π–Acceptor Type Porphyrin Derivatives Assisted Defect Passivation for Efficient Hybrid Perovskite Solar Cells

AbstractIn recent years, hybrid perovskite solar cells (PSCs) have attracted much attention owing to their low cost, easy fabrication, and high photoelectric conversion efficiency. Nevertheless, solution‐processed perovskite films usually show substantial structural disorders, resulting in ion defects on the surface of lattice and grain boundaries. Herein, a series of D–π–A porphyrins coded as CS0, CS1, and CS2 that can effectively passivate the perovskite surface, increase VOC and FF, reduce the hysteresis effect, enhance power conversion efficiency to be higher than 22%, and improve the device stability is developed. The results in this study demonstrated that the donor–π–acceptor type porphyrin derivatives are promising passivators that can improve the cell performance of PSCs.

Improving Moisture/Thermal Stability and Efficiency of CH3NH3PbI3‐Based Perovskite Solar Cells via Gentle Butyl Acrylate Additive Strategy

Organic–inorganic halide perovskite solar cells (PSCs) are a new class of photovoltaic devices, which have attracted increasing interests due to high efficiency, low cost, and simple fabrication process. Although a remarkable enhancement in power conversion efficiency (PCE) has been achieved in the last decade, the stability issue, including high water/heat sensitivity and UV light‐induced degradation, has become one of the main obstacles for practical applications of PSCs. Herein, hydrophobic butyl acrylate with CO and CC groups is reported as a new additive to enhance the PCE and moisture/thermal stability of CH3NH3PbI3‐based PSCs, which improves the quality of the perovskite film by promoting defect passivation, constructing a suitable energy‐level alignment, and increasing the charge carrier lifetime in PSCs. Such an additive is easily introduced into PSCs without the need for thermal treatment, which is typically required by other additives, causing a negative effect on the efficiency. The CH3NH3PbI3‐based PSC with butyl acrylate additive shows a superior PCE of 20.0%, 19% higher than that of the unmodified device (16.8%), as well as much improved moisture/thermal stability. Herein, a facile way is provided to enhance the PCE and stability of CH3NH3PbI3‐based PSCs simultaneously, which facilitates the commercialization of PSCs.

High-Efficiency Organic Photovoltaic Cells With an Antimony Quantum Sheet Modified Hole Extraction Layer

2D materials with unique opto-electronic properties have shown immense potential for application in organic photovoltaics (OPVs). In this article, we reported a facile and efficient strategy to enhance the device performance of OPVs by doping 2D material of antimonene quantum sheets (AMQSs) into PEDOT:PSS emulsion. The interfacial properties between the hole extraction layer (HEL) and PBDB-T:ITIC-based active layer were properly meliorated, achieving boosted power conversion efficiency ( PCE ). Results indicate that the introduced AMQSs could help suppress the recombination loss and improve charge extraction efficiency. Over 8.09% enhancement of PCE is observed compared to that of the control cell with pure PEDOT:PSS. This work provides a simple and valid strategy of HEL modification to realize high efficiency OPVs.

Oxidization-Free Spiro-OMeTAD Hole-Transporting Layer for Efficient CsPbI2Br Perovskite Solar Cells.

The inorganic CsPbI2Br perovskite faces serious challenges of low phase stability and high moisture sensitivity. The moisture controllable process of a hole-transporting layer (HTL) is crucial for the development of stable and efficient inorganic perovskite solar cells (IPSCs). In this work, we proposed an oxidization-free spiro-OMeTAD hole-transport layer (HTL) with a preoxidized spiro-OMeTAD solution to prevent moisture and completely avoid the phase transition of CsPbI2Br from the α-phase to β-phase. The oxidization-free HTL exhibited improved surface hydrophobic properties, smoother morphology, and optimized energy-level alignment compared with a traditional HTL. As a result, the CsPbI2Br-based IPSCs achieved an efficiency of up to 14.2 and 86.6% of the initial power conversion efficiency (PCE) with 2000 h storage. Meanwhile, this oxidization-free HTL was applied in CH3NH3PbI3-based PSCs and obtained 13.8% PCE enhancement, which proved the universality of the solution preoxidization tactic. We believe that the oxidization-free HTL could be an efficient strategy to replace traditional HTLs and can be widely used in perovskite solar cells, especially in moisture-sensitive PSCs.

Enhancement of power conversion efficiency of dye-sensitized solar cells for indoor applications by using a highly responsive organic dye and tailoring the thickness of photoactive layer

Dye-sensitized solar cells (DSSCs) based on different configurations under various light intensity are characterized, where commercial N719 dye and synthesized D-Dye are used as photo-sensitizer. Regardless of cell configuration, organic D-Dye serves as an efficient photo-sensitizer, giving rise to high cell efficiency comparable with N719. The highest efficiency of 20.98% (Voc of 0.6 V, Jsc of 0.62 mA/cm2, FF of 0.71) is achieved as the front-illuminated rigid DSSC is constructed by applying 8 μm TiO2 layer under 6000 LUX illumination. At the same condition the efficiency of 19.69% (Voc of 0.63 V, Jsc of 0.57 mA/cm2, FF of 0.74) is recorded for N719. Higher efficiency for D-Dye is attributed to high response of its absorption spectrum to the emission spectrum of indoor T5 irradiance. Charge transfer resistance is measured to be 53.1 Ω for D-Dye in conjunction with 8 μm TiO2 which is higher than thicker TiO2 (10 μm and 12 μm) at 0.75 V applied bias under dark condition, indicating that reduction of TiO2 thickness facilitates charge transfer by suppressing charge recombination under low illuminations. A systematic study of the efficiency as a function of key factors like TiO2 thickness, electrode type, and light intensity is explored.