Design and simulation of HTL-free CuBi2O4 based thin film solar cells for performance efficiency above 36%

This computational study investigates the enhancements in the opto-electronic performance of thin-film silicon solar cells due to the use of different shapes of plasmonic metal core-silica shell nanoparticles embedded inside the Si absorbing substrate. The different shapes of the silver core-silica shell nanoparticles that were investigated in this study were cubes, cylinders, pyramids, spheres and spheroids, respectively. Due to morphology-dependent properties, various shaped nanoparticles show unique optical characteristics. The most significant enhancements in the performance of the thin-film solar cells were obtained using a pyramid shaped silver nanoparticle core that was encompassed within a hollow pyramid-shaped silica shell. The conclusion reached in this study were made through rigorous finite-difference time-domain (FDTD) simulations that calculated the plasmon resonance of the different shaped metal core-silica shell nanoparticles, optical absorption enhancement studies, short circuit current density (Jsc), open-circuit voltage (Voc), fillfactor, output power and optical near-field enhancements. The study concludes with a quick investigation of the feasibility of using a `sandwich' configuration where a spherical homogeneous metal nanoparticle was placed on top of the Si absorbing layer and a metal core-dielectric shell nanoparticle was embedded inside the Si layer to further enhance the opto-electrical performance of the thin-film solar cells.

Light management in thin-film silicon solar cells

Simple compound antimony selenide (Sb2Se3) is a promising emergent light absorber for photovoltaic applications benefiting from its outstanding photoelectric properties. Antimony selenide thin film solar cells however, are limited by low open circuit voltage due to carrier recombination at the metallic back contact interface. In this work, solar cell capacitance simulator (SCAPS) is used to interpret the effect of hole transport layers (HTL), i.e., transition metal oxides NiO and MoO x thin films on Sb2Se3 device characteristics. This reveals the critical role of NiO and MoO x in altering the energy band alignment and increasing device performance by the introduction of a high energy barrier to electrons at the rear absorber/metal interface. Close-space sublimation (CSS) and thermal evaporation (TE) techniques are applied to deposit Sb2Se3 layers in both substrate and superstrate thin film solar cells with NiO and MoO x HTLs incorporated into the device structure. The effect of the HTLs on Sb2Se3 crystallinity and solar cell performance is comprehensively studied. In superstrate device configuration, CSS-based Sb2Se3 solar cells with NiO HTL showed average improvements in open circuit voltage, short circuit current density and power conversion efficiency of 12%, 41%, and 42%, respectively, over the standard devices. Similarly, using a NiO HTL in TE-based Sb2Se3 devices improved open circuit voltage, short circuit current density and power conversion efficiency by 39%, 68%, and 92%, respectively.

In this study, as a novel approach to thin-film solar cells based on tin sulfide, an environmentally friendly material, we attempted to fabricate (Ge, Sn)S thin films for application in multi-junction solar cells. A (Ge0.42 Sn0.58)S thin film was prepared via co-evaporation. The (Ge0.42 Sn0.58)S thin film formed a (Ge, Sn)S solid solution, as confirmed by X-ray diffraction (XRD) and Raman spectroscopy analyses. The open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) of (Ge0.42 Sn0.58)S thin-film solar cells were 0.29 V, 6.92 mA/cm2, 0.34, and 0.67%, respectively; moreover, the device showed a band gap of 1.42–1.52 eV. We showed that solar cells can be realized even in a composition range with a relatively higher Ge concentration than the (Ge, Sn)S solar cells reported to date. This result enhances the feasibility of multi-junction SnS-system thin-film solar cells.

Over 15% efficient wide-band-gap Cu(In,Ga)S2 solar cell: Suppressing bulk and interface recombination through composition engineering

The development of wide-bandgap Cu(In,Ga)Se2 thin films is crucial in order to reach the theoretical Shockley–Queisser limit values in single-crystal solar cells. However, the performance of solar cells based on wide-bandgap thin film absorbers has lagged significantly compared to that of their narrow-bandgap counterparts. Herein, we develop a feasible strategy to improve the photovoltaic performance of wide-bandgap Cu(In,Ga)Se2 chalcopyrite thin-film solar cells by simultaneously doping with both RbF PDT and Te2− anions as dopants in the absorber layer during the three-stage co-evaporation process. Besides inducing significant change in the GGI gradient, the synergistic effect of the Te2− anion dopant is rather beneficial in terms of controlling grain size, defects in grain boundaries, and charge carrier lifetime for encouraging charge separation and extraction, which contributes to simultaneously boosting short-circuit current density and fill factor. Te-poor devices afford an impressive efficiency of 9.58%, compared to 6.43% for control devices. More importantly, the efficiency and Voc values obtained for wide-bandgap-based thin-film solar cells containing Te anions were the highest compared to their counterparts as reported in the literature. These results demonstrate the role of Te2− anions in wide-bandgap absorber thin films on the photovoltaic performance of thin-film solar cells and the potential of this approach for use in reasonable and effective design of highly efficient wide-bandgap thin-film solar cells.

High-performance methylammonium-free ideal-band-gap perovskite solar cells

The optical generation rate and surface recombination velocity (SRV) increasing with the created nano-holes depth, width, and number on the emitter layer of a thin-film silicon solar cell are studied. The trade-off between the optical generation rate and surface recombination velocity was exhibit in short-circuit current density (J sc ), Open-circuit voltage (V oc ), and conversion efficiency (η) using a two-step simulation. The simulated results indicated that a thin-film solar cell with a proper nano-holes structure on the emitter layer can be achieved a much high J sc and η performances.

Antimony selenide (Sb<sub>2</sub>Se<sub>3</sub>) has advantages of low-toxicity, abundant and excellent photoelectric properties. It is widely considered as one of the most promising light-harvesting materials for thin-film solar cells. However, the power conversion efficiency of the Sb<sub>2</sub>Se<sub>3</sub> thin-film solar cell is still far inferior to that of cadmium telluride, copper indium gallium selenium and perovskite solar cells. As known, the Sb<sub>2</sub>Se<sub>3</sub> solar cell performance is closely related to the light absorber layer (crystallinity, composition and bulk defect density, etc.), PN heterojunction quality (charge carrier concertation, energy band alignment and interface defect density, etc.) and back-contact barrier formation, which determines the process of carrier generation, excitation, relaxation, transfer and recombination. The low fill factor is one of the core problems that limit further efficiency improvement of Sb<sub>2</sub>Se<sub>3</sub> solar cells, which can be attributed to the high potential barrier at the back contact between the Mo electrode and Sb<sub>2</sub>Se<sub>3</sub>absorption layer. In this work, a heat treatment is applied to the Mo electrode to generate a MoO<sub>2</sub>buffer layer. It can be found that this buffer layer can inhibit MoSe<sub>2</sub> film growth, exhibiting better ohmic contact with Sb<sub>2</sub>Se<sub>3</sub> and reducing the back contact barrier of the solar cell. Sb<sub>2</sub>Se<sub>3</sub> thin film is prepared by an effective combination reaction involving sputtered and selenized Sb precursor. After introducing the MoO<sub>2</sub>buffer layer, it can also promote the formation of (hk1) (including (211), (221) and (002) etc.) preferentially oriented Sb<sub>2</sub>Se<sub>3</sub> thin films with average grain size over 1 μm. And the ratio of Sb and Se was optimized from 0.57 to 0.62, approaching the stoichiometric ratio of Sb<sub>2</sub>Se<sub>3</sub> thin film and inhibiting the formation of <em>V<sub>se</sub> </em>and <em>Sb<sub>Se</sub></em> defects. Finally, it enhances the open-circuit voltage (<em>V<sub>OC</sub></em>) of solar cells from 0.473 V to 0.502 V, short-circuit current density (<em>J<sub>SC</sub></em>) from 22.71 mA/cm<sup>2</sup> to 24.98 mA/cm<sup>2</sup>, and fill factor (<em>FF</em>) from 46.90% to 56.18%, establishing a promotion in power conversion efficiency (<em>PCE</em>) from 5.04% to 7.05%. This work proposes a facile strategy for interfacial treatment and elucidates the related carrier transport enhancement mechanism, paving a bright avenue to overcome the efficiency bottleneck of Sb<sub>2</sub>Se<sub>3</sub> thin film solar cells.

Antimony selenide (Sb<sub>2</sub>Se<sub>3</sub>) has advantages of low-toxicity, abundant and excellent photoelectric properties. It is widely considered as one of the most promising light-harvesting materials for thin-film solar cells. However, the power conversion efficiency of the Sb<sub>2</sub>Se<sub>3</sub> thin-film solar cell is still far inferior to that of cadmium telluride, copper indium gallium selenium and perovskite solar cells. As is well known, the Sb<sub>2</sub>Se<sub>3</sub> solar cell performance is closely related to the light absorber layer (crystallinity, composition, bulk defect density, etc.), PN heterojunction quality (charge carrier concertation, energy band alignment, interface defect density, etc.) and back-contact barrier formation, which determines the process of carrier generation, excitation, relaxation, transfer and recombination. The low fill factor is one of the core problems that limit further efficiency improvement of Sb<sub>2</sub>Se<sub>3</sub> solar cells, which can be attributed to the high potential barrier at the back contact between the Mo electrode and Sb<sub>2</sub>Se<sub>3</sub> absorption layer. In this work, a heat treatment is applied to the Mo electrode to generate a MoO<sub>2</sub> buffer layer. It can be found that this buffer layer can inhibit MoSe<sub>2</sub> film growth, exhibiting better Ohmic contact with Sb<sub>2</sub>Se<sub>3</sub>, and reducing the back contact barrier of the solar cell. The Sb<sub>2</sub>Se<sub>3</sub> thin film is prepared by an effective combination reaction involving sputtered and selenized Sb precursor. After introducing the MoO<sub>2</sub> buffer layer, it can also promote the formation of (<i>hk</i>1) (including (211), (221), (002), etc.) preferentially oriented Sb<sub>2</sub>Se<sub>3</sub> thin films with average grain size over 1 μm. And the ratio of Sb to Se is optimized from 0.57 to 0.62, approaching to the stoichiometric ratio of Sb<sub>2</sub>Se<sub>3</sub> thin film and inhibiting the formation of V<sub>se</sub> and Sb<sub>Se</sub> defects. Finally, it enhances the open-circuit voltage (<i>V</i><sub>OC</sub>) of solar cells from 0.473 to 0.502 V, the short-circuit current density (<i>J</i><sub>SC</sub>) from 22.71 to 24.98 mA/cm<sup>2</sup>, and the fill factor (FF) from 46.90% to 56.18%, thereby increasing the power conversion efficiency (PCE) from 5.04% to 7.05%. This work proposes a facile strategy for interfacial treatment and elucidates the related carrier transport enhancement mechanism, thus paving a bright avenue to breaking through the efficiency bottleneck of Sb<sub>2</sub>Se<sub>3</sub> thin film solar cells.

Materials and Light Management for High-Efficiency Thin-Film Silicon Solar Cells

This study investigates the effect of active and conductive layer thickness on photovoltaic performance in perovskite solar cells, addressing the need for efficient and sustainable energy solutions in light of current environmental challenges. Using OghmaNano software, we analyzed how variations in thickness of the perovskite, fluorine-doped tin oxide (FTO), and gold (Au) layers influence key performance metrics, including power conversion efficiency (PCE), fill factor (FF), open-circuit voltage (Voc), and short-circuit current density (Jsc). The ideal thicknesses identified for achieving maximum PCE are 775 nm for the perovskite layer, 50 nm for the FTO layer, and 100 nm for the Au layer. This study underscores the complex relationship between light absorption and charge transport in perovskite solar cells and highlights the importance of fine-tuning layer thickness for enhanced efficiency. The simulation-based approach used here proves valuable for its practical efficiency, reducing both time and cost compared to experimental fabrication.

Lead-free tin perovskite solar cells

This study uses Finite-Difference Time Domain (FDTD) simulations to investigate the possibility of using a “sandwich” nanoparticle configuration where a core (metal)-shell (dielectric) nanoparticle (NP) is embedded within the silicon absorbing substrate of a thin-film solar cell and is coupled with a silver nanoparticle placed on the top of the substrate to cumulatively increase the opto-electronic performance of the solar cells. The core-shell nanoparticle (Ag-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> core-shell NP) inserted inside the semiconductor absorbing layer contained an outer shell layer made of SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> that covered the inner silver nanoparticle core to allow the creation of conditions suitable for surface plasmon resonance (SPR) as the SPR requires a metal-dielectric interface. The solar cells coupled to the “sandwich” configuration of Ag NP and Ag-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> core-shell NP exhibited superior response when compared to a bare silicon substrate and with the silicon substrate coupled to a Ag-NP alone or Ag-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> core-shell nanoparticle alone, respectively, based on different performance parameters such as optical absorption enhancement, short-circuit current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> ), open-circuit voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> ), optical near-field enhancement, fill factor, output power generated and efficiency. Of the different configurations studied, the optimal results were achieved for the case of a AgNP with 160nm diameter placed on the top of the Silicon substrate and Ag-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> core-shell nanoparticle with 100nm diameter of the silver core and 5nm thick silica shell embedded inside the Si substrate at a height of 5nm below the Si substrate top surface. The results of this study indicate that such plasmonic “sandwich” configurations of Ag-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> core-shell NP together with Ag NP can potentially be used to significantly boost the opto-electronic performance of commercially available thin-film solar cells.

There is an important need for improvement in both cost and efficiency of photovoltaic cells. For improved efficiency a better understanding of solar cell performance is required. In this paper we propose an analytical kinetic model of thin-film silicon solar cell, which can provide an intuitive understanding of the effect of illumination on its charge carriers and electric current. The separate cases of homogeneous and inhomogeneous charge carrier generation rates across the device are investigated. Our model also provides for the study of the carrier transport within the quasi-neutral and depletion zones of the device, which is of importance for thin-film solar cells. Two boundary conditions based on (i) fixed surface recombination velocity at the electrodes and (ii) intrinsic conditions for large size devices are explored. The device short circuit current and open circuit voltage are found to increase with the decrease of surface recombination velocity at electrodes. The power conversion efficiency of thin film solar cells is observed to strongly depend on impurity doping concentrations. The developed analytical kinetic model can be used to optimize the design and performance of thin-film solar cells without involving highly complicating numerical codes to solve the corresponding drift-diffusion equations.