Bifacial Solar Cells Research Articles

Combining radiative cooling and light trapping strategies for improved performance of PERC bifacial silicon solar cells

This work investigates the impact of combining light trapping and radiative cooling on bifacial solar panels. While several techniques have been proposed to enhance the efficiency of solar panels, their combination can lead to suboptimal results. By numerically evaluating the light absorption and thermal balance of different panel configurations, we found that each side of the bifacial solar cell can be textured independently with a cross-effect of less than 4%. However, our results also indicate that improving visible light trapping can increase infrared absorption, leading to a heating effect that may offset the benefits of radiative cooling. These findings highlight the importance of balancing the factors that influence solar panel efficiency and provide quantitative insights that guide the development of more effective solar energy systems.

Optimization of bifacial Ge-incorporated Sb2Se3 thin-film solar cells by modeling Cu2O back buffer layer

We have investigated bifacial Ge-incorporated Sb2Se3 thin-film solar cells by modeling and simulating a back buffer layer including Cu2O to optimize the bifacial device performance. A Ge-incorporated Sb2Se3 absorber layer was grown using Vapor Transport Deposition to extract the input parameters for the simulation, followed by exploring the properties of the transparent back buffer layer. After selecting a Cu2O back buffer layer, we conducted the optimization study of bifacial Ge-doped Sb2Se3 devices by varying a set of devices and materials parameters. The optical bandgap is characterized as 1.23 eV for Ge-incorporated Sb2Se3 absorber and the absorption coefficient is 3 × 105 cm−1 at 600 nm. Using these input parameters, we simulated the device configuration of ZnO:Al/i-ZnO/CdS/Ge-Sb2Se3/back buffer layer/transparent conductive oxide. Firstly, we checked the impact of conduction and valence band offsets on device performance, indicating the valence band offset of the back buffer layer plays a significant role. In particular, zero or small positive valence band offset minimizes a Schottky hole barrier, which could reduce hole current clamping near the back buffer region. As for back buffer doping concentration, high back buffer doping concentration (1 × 1015 cm−3 or higher) is required to improve device performance even with zero valence band offset, whereas low absorber doping concentration (<1 × 1014 cm−3) enables higher efficiency due to the enlarged energy band bending. For bifacial device performance, a Cu2O back buffer layer is simulated by varying critical input parameters such as absorber thickness, doping concentration, and defect concentration near the back buffer interface. The best efficiency of front-side illumination is 19.7%, Voc (744.4 mV), Jsc (40.14 mA/cm2), and FF (66.1%) and that of the rear-side illumination is 13.0%, Voc (724.5 mV), Jsc (31.6 mA/cm2), and FF (56.7%). Consequently, the bifaciality factor is 66%.

Exploring Ln(III)-Ion-Based Luminescent Species as Down-Shifters for Photovoltaic Solar Cells.

In this work, we have compiled our research on lanthanide-based luminescent materials for use as down-shifter layers in photovoltaic (PV) mini-modules. The complexes we have prepared (C1-17), with formulas [Eu2(phen)2(bz)6] (C1), [Eu2(bphen)2(bz)6] (C2), [Eu(tta)3bphen] (C3), [Eu(bta)3pyz-phen] (C4), [Eu(tta)3pyz-phen] (C5), [Eu(bta)3me-phen] (C6), [Er(bta)3me-phen] (C7), [Yb(bta)3me-phen] (C8), [Gd(bta)3me-phen] (C9), [Yb(bta)3pyz-phen] (C10), [Er(tta)3pyz-phen] (C11), [Eu2(bz)4(tta)2(phen)2] (C12), [Gd2(bz)4(tta)2(phen)2] (C13), [EuTb(bz)4(tta)2(phen)2] (C14), [EuGd(bz)4(tta)2(phen)2] (C15), [Eu1.2Gd0.8(bz)4(tta)2(phen)2] (C16), and [Eu1.6Gd0.4(bz)4(tta)2(phen)2] (C17), can be grouped into three families based on their composition: Complexes C1-6 were synthesized using Eu3+ ions and phenanthroline derivatives as the neutral ligands and fluorinated β-diketonates as the anionic ligands. Complexes C7-11 were prepared with ligands similar to those of complexes C1-6 but were synthesized with Er3+, Yb3+, or Gd3+ ions. Complexes C12-17 have the general formula [M1M2(bz)4(tta)2(phen)2], where M1 and M2 can be Eu3+, Gd3+, or Tb3+ ions, and the ligands were benzoate (bz-), 2-thenoyltrifluoroacetone (tta-), and 1,10-phenanthroline (phen). Most of the complexes were characterized using X-ray techniques, and their photoluminescent properties were studied. We then assessed the impact of complexes in the C1-6 and C12-17 series on the EQE of PV mini-modules and examined the durability of one of the complexes (C6) in a climate chamber when embedded in PMMA and EVA films. This study emphasizes the methodology employed and the key findings, including enhanced mini-module efficiency. Additionally, we present promising results on the application of complex C6 in a bifacial solar cell.

High-efficiency n-TOPCon bifacial solar cells with selective poly-Si based passivating contacts

Improving the conversion efficiency of n-TOPCon solar cell is still a hot topic. The selective poly-Si based passivating contacts (Poly-SEs) are ideal candidates for reducing the parasitic absorption and contact resistivity of n-type silicon solar cells and for providing better current collection. In this work, we used LPCVD and the POCl3 tube furnace diffusion methods to fabricate the selective poly-Si based passivating contacts, and studied the influences of key process parameters of the SiOx layer formation process (the oxidation duration (toxidation) and the constant pressure duration (tpressure)), and POCl3 tube diffusion process parameters (the POCl3-N2 carrier gas flow rate at the deposition, deposition temperature, drive-in temperature) on the n+-poly-Si profiles, recombination current density (J0), contact resistivity (ρc) of n-TOPCon solar cells. The results showed that the toxidation and tpressure had a significant impact on J0 and ρc which were mainly related to the distribution number of O and Si4+ content on the growth of the SiOx layer. And the influence of the drive-in temperature of phosphorus (P) diffusion process on J0 value is stronger than that of the deposition temperature, which was mainly related to the chemical passivation of SiOx layer induced by P-indiffusion into Si at high temperature. The reduction in the thickness of poly-Si from 110 nm to 30 nm led to an increase in the short-circuit current density (Jsc) per nanometer of ∼0.0093 mA/cm2 per nm. The Poly-SEs were fabricated by 3D printing mask technology and secondary LPCVD/phosphorus diffusion with J0, n+ ≈ 5 fA/cm2 (n+-poly-Si layer ≈ 50 nm) and J0, metal,n++ ≈ 73.8 fA/cm2 (n++-poly-Si layer ≈ 110 nm), and the efficiency was improved by 0.12% owing to the increase in Jsc value of 0.28 mA/cm2. After optimizing the passivation process, the industrial-grade TOPCon bifacial cells reached an efficiency (Eff), Voc, Jsc, and FF values as high as 25.4%, 721 mV, 42.2 mA/cm2, and 83.5%, respectively.

Optimization of Bifacial Photovoltaics by Optical Systems Feasibility Study

Bifacial PV cells allow light to reach the cell from the rear, achieving rear side efficiencies from 60% to over 95%. The predicted annual bifacial gain in irradiance (rear / front) can be 5% to 30% depending mainly on the reflectivity of the ground (albedo). It can be increased by optical systems redirecting diffuse and direct solar radiation to the rear of the solar cell without solar tracking. The optical systems can work by the physical effects of refraction or reflection. Beside reflective gratings refractive prismatic systems can be applied, e.g., as micro-structures, which originally were developed to improve daylighting of deep rooms. Applications and production related variations are described. The arrangement of the optical system and PV module can vary according to the orientation and setup of the module, which may be in open spaces or integrated into buildings. The advantage of bifacial over monofacial cells is expressed by the “bifacial gain”. This is the additional part of the total energy that a bifacial PV system produces in comparison to a monofacial system with the same orientation and size. This additional yield is given in the literature as 5% to 30%, depending on the reflectivity of the ground and the cell type. For the redirection of solar radiation by micro-structured systems on HIT bifacial solar cells a bifacial gain of 51% to 68% can be assumed. These preliminary results have to be confirmed by tests.

Bandgap Optimization for Bifacial Tandem Solar Cells

Bifacial tandem solar cells can generate more power than their monofacial counterparts by exploiting albedo at their rear. Optimum bandgap (Eg) values for subcells in both two-terminal (2T) and four-terminal (4T) bifacial tandems under different albedos are discussed using radiative-recombination-limit calculations. Our investigation considers both AM1.5G and field spectra, incident on silicon-constrained and unconstrained tandems. We find that for an albedo in the 0.2–0.5 range for 2T tandems and ≥0.3 for 4T tandems, the optimal bottom Eg is ∼1.12 eV, indicating that silicon, besides practical purposes, can also theoretically be the best bottom cell. Furthermore, our work highlights that the 4T configuration may be more attractive than its 2T counterpart for bifacial deployment due to a higher theoretical energy yield with lower sensitivities to albedo variations. To maximize 2T-tandem power conversion efficiency, counterintuitively, rather than precise current matching, the subcell with the highest fill factor needs to be current-limiting.

Design of a new static solar concentrator with a high concentration ratio and a large acceptance angle based on bifacial solar cells

Abstract Solar concentrators are used in solar photovoltaic systems to lower the cost of producing electricity. In this situation, fewer solar cells can be used, lowering the overall cost of the system. The purpose of this article is to design, construct, install and test a stationary (non-tracking) concentrating system in Irbid, Jordan. Bifacial solar cells are used in the design. Two concentrator designs (with the same concentration ratio) are experimentally tested. Conc-A has a parabolic shape in the lower part but flat reflecting walls, whereas Conc-B has a standard compound parabolic shape in all parts. The receiving solar cells are arranged in three distinct positions in each concentrator. The results reveal that the output power from both concentrators is affected by the placement of the receiving solar cells within the concentrator. It has also been found that concentrators with flat reflecting walls perform better than those with parabolic reflecting walls. Conc-A’s power collection is ~198% greater than that of a non-concentrating device. When Conc-B is used, the increase in power is ~181%.

A Review of Different Types of Solar Cell Materials Employed in Bifacial Solar Photovoltaic Panel

Conventionally accessible silicon solar cells experience two major drawbacks, such as reduced efficiency and increased fabrication costs. The prospects for the reduction in the cost of the photovoltaic form of energy conversion are bifacial solar cells. Bifacial solar cells show potential opportunity in reducing the cost of solar energy conversion when analyzed with respect to monofacial cells. The bifacial solar cells exploit sunlight occurrence on both sides of the cell more efficiently. Bifacial-based solar photovoltaic (PV) is a technology that increases the generation of electrical energy per square meter of PV module through the utilization of light absorption from the albedo. This technology can generally be categorized based on the type of solar cell material and the fabrication technique. PV devices are classified as a silicon-based, thin film, organic, and advanced nano PV. This paper takes a second look at some recent initiatives and significant issues in enhancing the efficiency of bifacial solar cells from material sciences and chemical composition aspects. From this review, it is concluded that screen-printed solar cells have produced a maximum efficiency of 22%. Additionally, triode structure single-crystalline cells produced a maximum front side efficiency of 21.3% and rear side efficiency of 19.8%. Considering the recycling of solar panels, organic solar panels can be developed.

Corrosion effects in bifacial crystalline silicon PV modules; interactions between metallization and encapsulation

This study addresses the influence of different encapsulation materials on performance losses in bifacial PV modules after extended damp heat testing. The widely used ethylene vinyl acetate (EVA) is compared to polyolefin elastomers (POE) and thermoplastic polyolefins (TPO). We show that modules based on n-type bifacial solar cells (tunnel oxide passivated contact, TOPCON) are more prone to degradation than p-type (Passivated emitter rear cell, PERC) based laminates. More specifically, the front side metallization of these n-type cells corrodes under extended damp heat testing, yielding a decreased fill factor in the I–V characteristics and the appearance of dark spots and dark areas in electroluminescence imaging. The newer generation of encapsulant materials (POE and TPO), slowly replacing EVA in the modules commercialized today, demonstrate an improved protection of the metallization. Apart from the nature of the encapsulant, the cell type and the presence or absence of glass cover plates are also shown to influence the metal grid corrosion. To better understand the mechanisms at play, post-mortem analysis was carried out on small sized degraded PV laminates, by drilling out circular samples (“coring”) that could be analyzed in depth. The analyses revealed a weakened bond between the metallization and the silicon emitter, ultimately causing metal grid delamination. The proposed mechanism behind this delamination starts with the degradation of lead glass, which is part of the cell metallization grid and contains lead oxide (PbO). This compound is susceptible to dissolution in acidic environment.

Radio-frequency magnetron sputtering deposition process for In2O3:H transparent conductive oxide films for application in Cu(In,Ga)Se2 solar cells

Typical Cu(In,Ga)Se2 solar cells are deposited on an opaque molybdenum back contact. However, for applications such as bifacial, semi-transparent or tandem solar cells a transparent back contact is required, for which various transparent conductive oxides have been tested, such as indium- or fluorine-doped tin oxide, and hydrogen-doped indium oxide. Here, a radio-frequency magnetron sputtering deposition process for In2O3:H (IOH) is investigated, where H is supplied from a Ar/H2 (5%) mixed gas and oxygen is pulsed during the entire deposition at room temperature. After deposition, the films are post-annealed in vacuum to optimize their optoelectronic properties. The oxygen plays an important role for the optoelectronic properties, where a high content of oxygen allows higher transparency but also increases the film sheet resistance. Optimum oxygen and Ar/H2 partial pressures of 3.2 × 10−2 Pa and 13×10−2 Pa, respectively, were found, producing IOH films with average visible transparency of 87% and sheet resistance after annealing of 19 Ohm/sq.

Cracked Film Lithography with CuGaOx Buffers for Bifacial CdTe Photovoltaics.

Bifacial CdTe solar cells with greater power density than the monofacial baselines are demonstrated by using a CuGaOx rear interface buffer that passivates while reducing sheet resistance and contact resistance. Inserting CuGaOx between the CdTe and Au increases mean power density from 18.0±0.5 to 19.8±0.4mWcm-2 for one sun front illumination. However, coupling CuGaOx with a transparent conductive oxide leads to an electrical barrier. Instead, CuGaOx is integrated with cracked film lithography (CFL)-patterned metal grids. CFL grid wires are spaced narrowly enough (≈10µm) to alleviate semiconductor resistance while retaining enough passivation and transmittance for a bifacial power gain: bifacial CuGaOx /CFL grids generate 19.1±0.6mWcm-2 for 1 sun front + 0.08 sun rear illumination and 20.0±0.6mWcm-2 at 1 sun front + 0.52 sun rear-the highest reported power density at field albedo conditions for a scaled polycrystalline absorber.

Comparative Study of Half Cut Solar Cell and Bifacial Solar Cell with Standard Solar Cell

The main purpose of this thesis is to make comparative study of half cut solar cell and bifacial solar cell with standard solar cell. The main procedure of this thesis was divided into three parts. The first part presents the detailed explanation about the solar cell. The second part shows the information about half cut solar cell . The third part shows the information about bifacial solar cell. This part has included a carefully study in order to choose the most correctly and the financially modules and inverters for the systems. The last two part shows the comparative study of the different PV systems. This part has presented the necessary number of modules and inverters, the total necessary area and the economic analysis for each system. The simulation of the solar cell was done by the software MATLAB/SIMULINK. After the analysis of the results of the different solar cell, it was possible to see which cell technology will be preferable for this system.

Bifacial Dye-Sensitized Solar Cells Utilizing Visible and NIR Dyes: Implications of Dye Adsorption Behaviour

Bifacial dye-sensitized solar cells (DSSCs) were fabricated utilizing dye cocktails of two dyes, Z-907 and SQ-140, which have complementary light absorption and photon harvesting in the visible and near-infrared wavelength regions, for panchromatic photon harvesting. The investigation of the rate of dye adsorption and the binding strengths of the dyes on mesoporous TiO2 corroborated the finding that the Z-907 dye showed a rate of dye adsorption that was about >15 times slower and a binding that was about 3 times stronger on mesoporous TiO2 as compared to SQ-140. Utilizing the dye cocktails Z-907 and SQ-140 from ethanol, the formation of the dye bilayer, which was significantly influenced by the ratio of dyes and adsorption time, was demonstrated. It was demonstrated that the dyes of Z-907 and SQ-140 prepared in 1:9 or 9:1 molar ratios favoured the dye bilayer formation by subtly controlling the adsorption time. In contrast, the 1:1 ratio counterpart was prone to form mixed dye adsorption; the best performance of the BF-DSSCs was shown when a dye cocktail of Z-907 and SQ-140 in a molar 9:1 ratio was used to prepare a photoanode for 1 h of dye adsorption. The BF-DSSCs thus exhibited PCEs of 4.23% and 3.48% upon the front and rear side light illuminations, a cumulated PCE of 7.71%, and a very good BBF of 83%.

High work function thermally stable OMO-based transparent electrode for optoelectronic applications

Ultrathin metal films (UTMFs) have emerged as a potential contender as a transparent electrode (TE) in various optoelectronic applications. Oxide-metal-oxide (OMO) based TEs incorporating UTMFs are the new state-of-the-art approach towards fabricating high-performance indium-free TEs. Here, we have demonstrated an OMO-based indium-free TE utilizing nickel oxide (NiO) and silver (Ag) as oxide and metal films respectively. Optical constants of NiO and Ag obtained from spectroscopic ellipsometry have been utilized in determining the optimum thickness of alternate layers in the OMO stack using a MATLAB code based on the transfer matrix method. To minimize the reflection losses, 40 nm of NiO as films was deposited on either side of the Ag film. A highly transparent NiO/Ag/NiO (NAN) electrode has been obtained by the physical vapor deposition technique. The fabricated TE shows high transmittance >82% in the visible region along with a low sheet resistance below 6 Ω/□. To analyze the thermal stability of NAN-TE, it has been treated at different elevated temperatures. It was observed that NAN-TE shows better thermal stability in comparison to commercially available ITO-TE. The incorporation of NiO as an overcoat layer results in enhancing the work function to 5.35 eV as measured by Kelvin Probe Force Microscopy (KPFM). The high average visible transmittance, high work function, low sheet resistance, and high-temperature tolerance make the developed TE compatible with optoelectronic devices where high-temperature processing is necessary. To verify the same a bifacial perovskite solar cell is fabricated incorporating the NAN-TE as top TE and a power conversion efficiency (PCE) of 3.51% and 2.56% is obtained by illuminating the fabricated device from FTO and NAN side.

Improvement in the Performance of P-Type Tunnel Oxide Passivated Contact Solar Cell With Selective Tunneling Junctions Underneath the Contacts on Front Side

Industrial silicon solar cells are now moving further from passivated emitter and rear contact (PERC) toward Tunnel Oxide Passivated contact (TOPCon) technology. The efficiency of the PERC solar cell is improved by TOPCon technology, in which the rear side is fully passivated by an oxide/poly-Si tunneling junction. The performance of a TOPCon solar cell may further be improved by the incorporation of selective tunneling junctions underneath the front contacts. Some fabrications have been reported on a similar structure for an n-type Si substrate but they have not achieved the expected results. Also, a detailed study has not been done yet. Using 3-D sentaurus technology computer aided design (TCAD) simulation software, a detailed analysis has been done on the modified structure through the optimization of the tunnel oxides, the interfaces, the n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">++</sup> poly-Si layer, the selective (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">++</sup> -poly-Si) tunneling junctions underneath the front contacts, etc., which has not been done earlier. It is seen that a thick n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">++</sup> poly-Si layer causes parasitic absorption of light, whereas a very thin poly-Si layer cannot provide sufficient field for tunneling of carriers. A thicker tunnel oxide produces a high series resistance, whereas a very thin tunnel oxide cannot restrict the minority carriers to reach to the contacts. Therefore, an optimization is required and the optimization is done based on a fabricated bifacial p-TOPCon solar cell reported in the literature with an efficiency of 21.2% and bulk lifetime of 200 μs. After performing all the modifications in the fabricated reference cell and optimizing different parameters, the efficiency is improved by 3.5% in absolute. The efficiency is further improved to 25.4% with the bulk lifetime of 1 ms.

Optically asymmetric down-shifting films for highly efficient photovoltaics

Quantum dots (QDs) have been regarded as promising spectral converters for photovoltaic (PV) devices owing to their excellent photoluminescence (PL) characteristics. Herein, we report a highly-efficient QD hierarchical (QD-Hie) film that elevates the PV performance by integrating QDs with micro/nano hierarchical structures. The proposed film was designed to ensure low reflectance for incident light (air-to-device) and high reflectance for escape light (device-to-air), obtaining a light-trapping effect to increase the absorption of PVs at wide incident angles. The trapped ultraviolet photons in our film promoted the downshifting property of the QDs and amplified the generation of visible photons, thereby enhancing the PL characteristics of QDs up to 3.71 times with independency of the incidence angle. Furthermore, the hierarchical structure restricts the outward release of converted QDPL, ensuring high availability of the down-shifted photons to PVs. The optical benefit of our film was maximized by attaching them on both sides of bifacial semi-transparent dye-sensitized solar cells, resulting in the short-circuit current density (JSC) improvement of up to 25.97% under AM 1.5G illumination. Along with its high versatility and outstanding JSC increments, our study presents a new perspective of advanced spectral converting layers and provides practical viability for various optoelectronic devices.

Self-protecting concave microstructures on glass surface for daytime radiative cooling in bifacial solar cells

As a passive and compact cooling mechanism, radiative cooling is lightweight and does not consume energy. Especially for the new popular bifacial PV modules, the traditional cooling method, containing air cooling with heat sink, water cooling, phase change cooling etc. would not be suitable, and the passive radiative cooling is attracting extensive attention. In PV radiative cooling field, high emissivity materials with high visible transparency are usually used to improve the radiative heat dissipation capacity of solar cell. Most of them are polymer materials with micro-nano structural surface, which have the defects of oxidation yellowing and structural loss, and the radiative cooling film itself adds an extra thermal resistance. Hence, a variety of concave micro-nano structures based on photovoltaic glass are proposed in this work, which are protected on the inner surface of glass, making the slender structure possible, and a strong heat dissipation effect while retaining self-cleaning characteristics without covering radiative cooling films. Moreover, the spectral properties of seven kinds of structures are numerical studied, and the solar cell temperature is calculated, as well as photoelectric conversion efficiency and cooling power. The results show that the visible light transmittance of these structures is basically higher than 0.9, the emissivity of some structures between 4 and 25 μm can reach more than 0.95, the solar cell can be cooled by 2–6 °C under common environmental conditions. When Ta = 30 °C and hc = 12 W/(m2·°C), electrical efficiency is improved by 0.47% absolutely by the hemisphere, Pcooling can reach about 330 W/m2. As they are designed inside the glass, the hardness and life are greatly improved compared with previous study achievements, allowing large application potential in glass packaging PV field.

All-Vacuum-Deposited Bifacial Cu2ZnSnSe4 Photovoltaic Cells with Sputtered Cd-Free Buffer Layer

By depositing metal precursors on fluorine-doped tin oxide substrates using evaporation and postselenisation and modifying the number of stacked metallic precursor layers, this study systematically analysed the effect of cation changes on the absorber layer and the solar cell properties of Cu2ZnSnSe4 (CZTSe). Furthermore, in this study, an all-vacuum method was adopted to prepare a cadmium-free bifacial CZTSe solar cell and conducted damp heat tests on the device. The findings indicate that the increase in the number of stacked metallic precursor layers suppresses secondary phase generation, thereby enhancing the film performance and bifacial solar cell characteristics. The cadmium-free bifacial CZTSe solar cell prepared in this study exhibited the efficiency of 4.13% under bifacial incident light. Moreover, the degradation of the device was effectively mitigated in the damp heat tests compared with previously reported devices with metal substrates. These findings can provide new directions for research and lead to novel applications for CZTSe solar cells in the future.

Combustion-Assisted Polyol Reduction Method to Prepare Highly Transparent and Efficient Pt Counter Electrodes for Bifacial Dye-Sensitized Solar Cells.

A combustion-assisted polyol reduction (CPR) method has been developed to deposit electrocatalytically efficient and transparent Pt counter electrodes (CEs) for bifacial dye-sensitized solar cells (DSSCs). Compared with conventional thermal decomposition of Pt precursors, CPR allows for a decrease in reduction temperature to 150 °C. The low-temperature processing is attributed to adding an organic fuel, acetylacetone (Hacac), which provides extra heat to lower reduction energy. In addition, the stable Pt complexes can simultaneously be formed in ethylene glycol (EG) and Hacac system, which leads to Pt nanoparticle size regulation. A ratio of Hacac to EG is optimized to achieve excellent electrocatalytic activity and high visible light transmittance for CEs. The bifacial DSSCs fabricated with CPR-Pt CEs (EG : Hacac=1 : 16) reach efficiencies of 6.71±0.16% and 6.41±0.15% in front and back irradiations, respectively.

Suppression of SnS2 Secondary Phase on Cu2ZnSnS4 Solar Cells Using Multi-Metallic Stacked Nanolayers.

In Cu2ZnSnS4 (CZTS) solar cells, it is crucial to suppress the generation of and remove the SnS2 secondary phase to improve the solar cell characteristics, as the SnS2 secondary phase affects the barrier for carrier collection and diode characteristics of the device. In this study, the nano-metallic precursor was modified to effectively suppress the generation of the SnS2 secondary phase on the surface and simultaneously improve the uniformity and quality of the thin film. The CZTS bifacial solar cells prepared via the proposed method exhibited significantly improved junction-rectifying characteristics, as the efficiency was improved to 1.59%. The proposed method to figurremove SnS2 is effective, simple, and environmentally friendly.