Power Conversion Efficiency Of Solar Cells Research Articles

Effect of Co doping for improved photovoltaic performance of dye-sensitized solar cells in BaSnO3 nanostructures

Addition of Co2+ into pristine BaSnO3 (BSO) nanostructures enhanced dye-sensitized solar cell (DSSC) power conversion efficiency (PCE), and the tuned efficiency of 8.22% for 3 at.% of Co doped BSO photoanode with surface treatment and scattering layer, due to the reduction in lattice mismatch and recombination effect. Impedance spectra confirms the DSSC performance by its better photoelectron transport in BSO:Co (483 ohm) compared with pristine photoanode (1202 ohm).

High Open-circuit Voltage and Low Voltage Loss in All-polymer Solar Cell with a Poly(coronenediimide-vinylene) Acceptor

Reducing the voltage loss (Vloss) is a critical factor in optimizing the open-circuit voltage (Voc) and overall power-conversion efficiency (PCE) of polymer solar cells. In the current work, by designing a novel electron-accepting unit of coronenediimide (CDI) and using it as the main functional building block, a new polymer acceptor CDI-V is developed and applied to fabricate all-polymer solar cells. Compared with the perylenediimide-based polymer acceptors we previously reported, the current CDI-V polymer possesses a noticeably elevated lowest unoccupied molecular orbital (LUMO). Thereby, by virtue of the enlarged energy gap between the donor HOMO and acceptor LUMO, a high Voc value of 1.05 V is achieved by the all-polymer photovolatic device, along with an impressively low Vloss of 0.55 V. As remarkably, in spite of an extremely small LUMO level offset of 0.01 eV exhibited by the donor and acceptor polymers, effective charge separation still takes place in the all-polymer device, as evidenced by a proper short-circuit current (Jsc) of 9.5 mA·cm2 and a decent PCE of 4.63%.

Co-Solvent Controllable Engineering of MA0.5FA0.5Pb0.8Sn0.2I3 Lead–Tin Mixed Perovskites for Inverted Perovskite Solar Cells with Improved Stability

Use of a lead–tin mixed perovskite is generally considered an effective method to broaden the absorption wavelength of perovskite thin films. However, the preparation of lead–tin mixed perovskites is a major challenge due to the multivalent state of tin and stability in the atmosphere. This study attempted to replace the organic cation and metal elements of perovskites with a relatively thermal stable formamidinium (FA+) and a more environmentally friendly tin element. MA0.5FA0.5Pb0.8Sn0.2I3 lead–tin mixed perovskite thin films were prepared with the one-step spin-coating method. By adjusting the dimethylformamide (DMF):dimethyl sulfoxide (DMSO) concentration ratio of the lead–tin mixed perovskite precursor solution, the surface morphologies, crystallinity, and light-absorbing properties of the films were changed during synthesis to optimize the lead–tin mixed perovskite films as a light-absorbing layer of the inverted perovskite solar cells. The quality of the prepared lead–tin mixed perovskite film was the highest when the ratio of DMF:DMSO = 1:4. The power-conversion efficiency of the perovskite solar cell prepared with the film was 8.05%.

Predicting Device Parameters for Dye-Sensitized Solar Cells from Electronic Structure Calculations to Reproduce Experiment

Given that improvements to the power-conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs) have slowed in recent years, a means to accurately predict the device parameters yielded by tr...

Transparent Platinum Counter Electrode Prepared by Polyol Reduction for Bifacial, Dye-Sensitized Solar Cells.

Pt catalytic nanoparticles on F-doped SnO2/glass substrates were prepared by polyol reduction below 200 °C. The polyol reduction resulted in better transparency of the counter electrode and high power-conversion efficiency (PCE) of the resultant dye-sensitized solar cells (DSSCs) compared to conventional thermal reduction. The PCEs of the DSSCs with 5 μm-thick TiO2 photoanodes were 6.55% and 5.01% under front and back illumination conditions, respectively. The back/front efficiency ratio is very promising for efficient bifacial DSSCs.

Atomistic Origins of the Limited Phase Stability of Cs+-Rich FAxCs(1–x)PbI3 Mixtures

Mixed cation perovskites, [HC(NH2)2]xCs(1–x)PbI3, (FAxCs(1–x)PbI3) with x = 0.8, achieve high solar cell power conversion efficiencies while exhibiting long-term stability under ambient conditions....

Boosting Performance of Non‐Fullerene Organic Solar Cells by 2D g‐C3N4 Doped PEDOT:PSS

AbstractThe power‐conversion efficiency (PCE) of single‐junction organic solar cells (OSCs) has exceeded 16% thanks to the development of non‐fullerene acceptor materials and morphological optimization of active layer. In addition, interfacial engineering always plays a crucial role in further improving the performance of OSCs based on a well‐established active‐layer system. Doping of graphitic carbon nitride (g‐C3N4) into poly(3,4‐ethylene‐dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as a hole transport layer (HTL) for PM6:Y6‐based OSCs is reported, boosting the PCE to almost 16.4%. After being added into the PEDOT:PSS, the g‐C3N4 as a Bronsted base can be protonated, weakening the shield effect of insulating PSS on conductive PEDOT, which enables exposures of more PEDOT chains on the surface of PEDOT:PSS core‐shell structure, and thus increasing the conductivity. Therefore, at the interface between g‐C3N4 doped HTL and PM6:Y6 layer, the charge transport is improved and the charge recombination is suppressed, leading to the increases of fill factor and short‐circuit current density of devices. This work demonstrates that doping g‐C3N4 into PEDOT:PSS is an efficient strategy to increase the conductivity of HTL, resulting in higher OSC performance.

Efficiency improvement of flexible Sb2Se3 solar cells with non-toxic buffer layer via interface engineering

Thin film Sb2Se3 solar cells have gained a worldwide attention as a highly potential Earth-abundant photovoltaic technology. While Sb2Se3 solar cells are typically fabricated in superstrate structure, substrate configuration devices offer versatility in substrate material choice particularly important for flexible devices. However, all substrate type Sb2Se3 solar cells use CdS as a buffer layer synthesized by chemical bath deposition method, during which Sb2Se3 surface is degraded limiting solar cell performance. Additionally, contamination layer has been reported to exist on Sb2Se3 surface after deposition under low vacuum conditions. In this study, we demonstrate a facile strategy to improve Sb2Se3 solar cell power conversion efficiency (PCE) by replacing CdS with In2S3 and applying a two-step treatment involving chemical etching and subsequent annealing. We show that a combined treatment which first removes the contamination layer and then passivates interface defects improves PCE more than three-fold, from 1.6% to 5.35%. Effective passivation of interface defects is ascribed to the formation of thin crystalline Sb2O3 layer on Sb2Se3 absorber surface after the treatment. In conclusion, optimized two-step treatment offers a simple and effective way to improve PCE and replacement of toxic CdS with In2S3 demonstrates new device design options towards flexible and non-toxic Sb2Se3 solar cells.

Preparation of high‐efficiency perovskite solar cells via doping Ag into CuO nanofibers as hole buffer layer

AbstractAg/CuO nanofibers (Nfs) with a diameter of 650 nm were successfully prepared via electrospinning Ag doped CuO nanofibers and then calcined at 450°C for 2 hours. By using Ag/CuO Nfs and PEDOT:PSS as the hole transport layer, an optimum perovskite solar cell power conversion efficiency (PCE) of 11.6% was achieved, which was 33% higher than that of the original perovskite solar cells (8.7%). The devices showed a high PCE because of the high cavity mobility of the Ag/CuO Nfs/PEDOT:PSS films. At the same time, the Ag/CuO Nfs could also slow down the hydrolysis and corrosion of the perovskite by acidic PEDOT:PSS, and increase the environmental stability of the solar cells.

N-Graphene/p-Silicon-based Schottky junction solar cell, with very high power conversion efficiency

We are presenting a solar cell consisting of electron-doped graphene (n-G)/holes-doped silicon (p-Si) Schottky junction, which provides a very high power conversion efficiency (PCE). The high PCE of our solar cell is caused by its high Schottky barrier height, which gives a very low value for the saturated reverse current (I0), and consequently, occurs a very low value of the current flowing through the forward-biased Schottky junction (value tending to zero). Therefore, as all photogenerated current goes to the external circuit, the solar cell PCE, we are presenting is very high, which exceeds the Shockley–Quiesser limit. It is noteworthy that the n-G/p-Si solar cells with resistance series Rs = 17.52 Ω, and Rs = 10.00 Ω presented PCE values ≈ 22.55%, and ≈ 39.51%, respectively. Since there is no current going through the Schottky junction, that n-G/p-Si solar cell operates similarly to an electrochemical generator. To get the characteristic parameters of our solar cell, we used an analytical/numerical methodology.

Lanthanide-containing polyoxometalate as luminescent down-conversion material for improved printable perovskite solar cells

Full utilization of the incident light is an effective strategy to enhance photovoltaic performance of perovskite solar cells (PSCs). Here, we used lanthanide-containing polyoxometalate Na9[EuW10O36] (EuW10) as a luminescent down-conversion material incorporated in mesoporous TiO2 layer for boosting the power conversion efficiency (PCE) of the printable hole transport material-free PSCs. The EuW10 can convert the high energy photons into the low energy visible photons matched well with the absorption of perovskite, so that photogenerated current carriers increase substantially. This research represents the first example of using lanthanide-containing polyoxometalate as down-conversion materials to effectively improve PCE in solar cells. Compared with pristine TiO2 based PSCs, the EuW10-TiO2 based PSCs showed an enhanced power conversion efficiency (PCE) from 11.42% to 14.36% and obtained a remarkable photocurrent density of 23.46 mA/cm2. Besides, the EuW10-TiO2 based device exhibited a better long-term stability, which could maintain 98% initial efficiency after storage for 14 days. Since the efficiency of the printable perovskite solar cells has been a key factor to achieve commercial implementations, we consider that the results from this work demonstrate a new kind of down-conversion materials to boost PCE and stability.

All-inorganic, hole-transporting-layer-free, carbon-based CsPbIBr2 planar solar cells with ZnO as electron-transporting materials

In this paper, all-inorganic, hole-transporting-layer-free (HTLF), carbon-based CsPbIBr2 planar solar cells with zinc oxide (ZnO) as electron-transporting materials (ETMs) were studied for the first time. The reported all-inorganic, HTLF, carbon-based cesium lead iodide dibromide (CsPbIBr2) solar cells used titanium dioxide (TiO2) as ETMs, which usually required a high sintering temperature of 500 °C. Here, ZnO ETMs were annealed at 120 °C. The highest power conversion efficiency (PCE) of 7.60%, with a short-circuit current (Jsc) of 11.60 mA/cm2, an open-circuit voltage (Voc) of 1.03 V and the fill factor (FF) of 0.63, was obtained. Furthermore, the thermal and humid stabilities of the solar cells were studied. The perovskite solar cells were placed at 10% humidity and room temperature for 624 h and the PCE of perovskite solar cells only decreased by 10%. While the perovskite solar cells were placed at 80 °C and 0% humidity for 192 h, the PCE of the solar cells decreased by 4%.

Design and simulation of perovskite solar cells with Gaussian structured gradient-index optics.

To unlock the full potential of the perovskite solar cell (PSC) photocurrent density and power conversion efficiency, the topic of optical management and design optimization is of absolute importance. Here, we propose a gradient-index optical design of the PSC based on a Gaussian-type front-side glass structure. Numerical simulations clarify a broadband light-harvesting response of the new design, showing that a maximal photocurrent density of 23.35 mA/cm2 may be expected, which is an increase by 1.21 mA/cm2 compared with that of the traditional flat-glass counterpart (22.14 mA/cm2). Comprehensive analysis of the electric field distributions elucidates the light-trapping mechanism. Furthermore, PSCs having the Gaussian index profile display superior optical properties and performance compared to those of the uniform index counterpart under varying conditions of perovskite layer thicknesses and incident angles. The simulation results in this study provide an effective design scheme to promote optical absorption in PSCs.

Three-dimensional ZnO/ZnxCd1−xS/CdS nanostructures modified by microwave hydrothermal reaction-deposited CdSe quantum dots for chemical solar cells

Effective interfaces composed of smart materials could play a critical role in the rapid transfer and separation of charges to achieve the high power-conversion efficiency of solar cells. In this work, we report an efficient chemical solar cell that uses a ZnO/ZnxCd1−xS/CdS structure, modified with CdSe deposited with a microwave hydrothermal technique, for rapid transport of charges using a frame construction to allow for reuse. The morphology, nanostructure, and reaction mechanisms of CdS nanorods and the ZnxCd1−xS layer were systematically investigated. The results indicated that light absorption expands from 550 nm of CdS to 700 nm because of the absorption of nearly all the visible light by deposited CdSe quantum dots. The effects of the compositional structure on cell performance are investigated to reveal the enhancement mechanism, which is mainly attributed to the suitable nano-branch structure, high light absorbability, low charge transfer resistance, and low recombination rate. This work demonstrates a potential universal method of designing an interface with a multi-component composite for efficient charge transport and separation, not only in chemical solar cells but with extensions to photocatalysis and water splitting uses as well.

Synthesis of Si and CdTe quantum dots and their combined use as down-shifting photoluminescent centers in Si solar cells

This paper describes the synthesis and characterization of Si and CdTe quantum dots (QDs) and their use, either on their own or combined, as photoluminescent (PL) down-shifting nanostructured coatings aimed to enhance the photovoltaic efficiency of polycrystalline silicon solar cells. To this end, the front face of a set of silicon cells was coated with different volume ratios of the above-mentioned QDs, or some of its mixtures, dispersed in PMMA layers. Previously, the absorption and the PL (exc = 380 nm) response of the dispersions of the QDs were measured. It was observed that the PL response of the mixtures was strongly affected in location, spread, and intensity of the emission peak according to the volume ratio involved. As compared to the unmixed CdTe samples, a notorious red-shift of the main peak location was obtained for a couple of mixed QDs’ dispersions, which was one of the project objectives given that Si solar cells respond better to photons with wavelengths in the 650–700 nm range. This effect was confirmed in a set of polycrystalline Si solar cells covered with and without nanostructured PMMA/QDs layers tested under AM 1.5G solar simulator conditions. It was found that the use of the proposed mixtures of QDs gave an increase of 1.53% in solar cell power conversion efficiency.

Band gap shift of Cu2ZnSnS4 thin film by residual stress

The band gap tuning technology can contribute to improvement of power-conversion efficiency (PCE) of solar cells. In this study, the band gap of the Cu2ZnSnS4 (CZTS) thin film, which was changed by residual strain, has been reported. When the thin film was deposited on soda-lime glasses, the substrate temperatures was fixed by an electric heater. Through the analysis of XRD patterns and Raman spectra, the presence of a second phase, of SnS2, ZnS, or Cu4Sn7S16, was confirmed. Using XRD patterns, the lattice constants and residual strains of the CZTS thin films were determined. The CZTS thin film which had the smallest lattice constant c was under the largest residual compressive stress. The residual strain made Raman peaks and band gaps of CZTS photoabsorbers change linearly. The line slopes in the plots of Raman peak position and band gap as function of residual strain were determined to be 572.7 cm−1 per unit strain and 93.51 eV per unit strain, respectively. This result indicates that the band gap of CZTS photoabsorbers can be tuned by controlling residual stress.

Dual-sized TiO2 nanoparticles as scaffold layers in carbon-based mesoscopic perovskite solar cells with enhanced performance

Dual-sized TiO2 scaffold layer was successfully prepared by dispersing appropriate 100 nm-sized TiO2 nanoparticles into conventional TiO2 scaffold layer composed of 25 nm-sized TiO2 nanoparticles, and then applied to carbon-based mesoscopic perovskite solar cells. Compared with conventional TiO2 scaffold layer, the dual-sized TiO2 scaffold layer not only exhibits higher light-harvesting efficiency due to the better light scattering ability of 100 nm-sized TiO2 nanoparticles, but also shows significantly improved infiltration of perovskite into the scaffold layer because of the larger voids formed within the dual-sized TiO2 scaffold layer. These merits lead to much higher short-circuit photocurrent density and thus power-conversion efficiency. The average short-circuit photocurrent density and power-conversion efficiency of the carbon-based mesoscopic perovskite solar cell employing dual-sized TiO2 scaffold layer with an 14.4% mass fraction of 100 nm-sized TiO2 nanoparticles are 19.31% and 18.57% higher than those of the cell based on conventional TiO2 scaffold layer. The power-conversion efficiency is further improved to 11.69% by optimizing the thickness of the dual-sized TiO2 scaffold layer. The combination of superior light harvesting capability and complete perovskite infiltration make the dual-sized TiO2 film a good candidate as the scaffold layer for carbon-based mesoscopic perovskite solar cells.

Significant enhancement of photo-physicochemical properties of Yb doped copper oxide thin films for efficient solid-state solar cell

Pure and Ytterbium (Yb) doped Copper oxide (CuO) thin films with different wt% (0, 1, 2, 3, 4, and 5) are deposited on glass substrates using chemical spray pyrolysis technique at 300 °C and their performances in heterojunction solar cell are examined here. The structural characterization reveals the monoclinic crystal structure and an increase in crystallite size is observed for 3 wt% Yb doped CuO. All the films show optical absorption in the UV–Vis region and 3 wt% has a higher absorption coefficient. The generation of self-assembled one-dimensional (1D) microrod like structure is observed for 3 wt% Yb doped CuO sample. The 3 wt% Yb doped CuO film exhibits higher carrier concentration (6.91 × 1019 cm−3) and electrical conductivity (0.58 S cm−1). All the films perform single semicircle impedance nature and smaller radius semicircle for 3 wt%, which indicates low electrical resistivity. The higher dark current (0.5 mA) and photoresponse (0.62 mA) are observed for 3 wt% of Yb doped CuO film compared with pure and other wt%. The solar cell power conversion efficiency of 0.37% and 1.8% is observed for pure and 3 wt% of Yb doped CuO respectively. It is concluded that 3 wt% of Yb doped CuO thin film can be used as an efficient absorber layer for fabricating heterojunction solar cell.

All-polymer solar cells based on photostable bis(perylene diimide) acceptor polymers

Fullerene-free organic photovoltaics have recently reached impressive power conversion efficiencies above 14% for single junctions, increasing their competitiveness with respect to alternative thin-film technologies. In most record devices, electron-donating conjugated polymers are combined with novel generation small molecule acceptors. All-polymer organic solar cells, on the other hand, still lag behind in efficiency, although they have specific advantages in terms of ink formulation and long-term operational stability. Another point of attention is the synthetic complexity of the active layer materials, notably on the side of the new acceptor molecules. Therefore, the present study focuses on the implementation of the stable and cost-effective perylene diimide structure as the key component of high-performance electron-accepting polymers. The synthesis, structural and optoelectronic characterization of four push-pull type copolymers containing the electron-deficient bis(perylene diimide) (bis-PDI) unit is reported, as well as the photovoltaic analysis of these acceptor materials in combination with a well-known donor polymer (PTB7-Th). The acceptor polymers differ in the electron-rich part of the alternating push-pull structure and their solar cell power conversion efficiencies range from 3.2 to 4.7%. The maximum efficiency - the best performance achieved with a bis-PDI polymer so far - is obtained for the structurally most simple polymer, containing merely thiophene as the electron-rich building block. Controlled degradation under blue light in air is monitored by the bleaching of the relevant UV–Vis absorption bands, demonstrating high stability for the bis-PDI-thiophene containing polymers as compared to some prototype small molecule acceptors (FBR and ITIC).

Concentration effect of aluminum nitrate on the Crystalline−Amorphous transition between Al-doped ZnO nanorods and nanostructures prepared by electrochemical deposition

In this study, an electrochemical deposition was conducted to prepare Al:ZnO. Products in three distinct phases were obtained depending on the [Al3+] added in the bath of 2.0 mM zinc nitrate. For convenient description, [Al3+] (total range 0–1000 μM) was termed as dilute (i.e., [Al3+] < 60 μM), medium (i.e. 60 μM < [Al3+] < 100 μM), and concentrated (i.e., [Al3+] > 250 μM). Field-emission scanning electron microscopy revealed that a compact phase of nanorods was deposited in the dilute [Al3+], a mixed phase consisting of nanorods and nanosheets was deposited in the medium [Al3+], and a loose phase of cloudy floc was produced in the concentrated [Al3+]. By analyzing the reaction products with grazing incidence X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy, we distinguished the crystal film of aluminum-doped zinc oxide nanorods from the amorphous hydroxides. Mott-Schottky measurements revealed that the specimen of nanorods doped with 2.84 at.% Al displays the highest carrier concentration (3.83 × 1018 cm−3) and demonstrates the highest electric conductivity among the specimens in a compact phase of nanorods. Photovoltaic tests showed that these films have fill factor and solar cell power conversion efficiency of 70.6 and 2.15%, respectively. By means of cathodic polarization and analysis of basic chemistry in aqueous solution, we propose a comprehensive mechanism to illustrate the type of products depending on [Al3+].