SiOx Patterned Based Substrates Implemented in Cu(In,Ga)Se2 Ultrathin Solar Cells: Optimum Thickness

Interface recombination in sub-µm optoelectronics has a major detrimental impact on devices’ performance, showing the need for tailored passivation strategies to reach a technological boost. In this work, SiOx passivation based substrates were developed and integrated into ultrathin Cu(In,Ga)Se2 (CIGS) solar cells. This study aims to understand the impact of a passivation strategy, which uses several SiOx layer thicknesses (3, 8, and 25 nm) integrated into high performance substrates (HPS). The experimental study is complemented with 3D Lumerical finite-difference time-domain (FDTD) and 2D Silvaco ATLAS optical and electrical simulations, respectively, to perform a decoupling of optical and electronic gains, allowing for a deep discussion on the impact of the SiOx layer thickness in the CIGS solar cell performance. This study shows that as the passivation layer thickness increases, a rise in parasitic losses is observed. Hence, a balance between beneficial passivation and optical effects with harmful architectural constraints defines a threshold thickness to attain the best solar cell performance. Analyzing their electrical parameters, the 8 nm novel SiOx based substrate achieved a light to power conversion efficiency value of 13.2 %, a 1.3 % absolute improvement over the conventional Mo substrate (without SiOx).info:eu-repo/semantics/submittedVersio

Depletion effects in moderately doped TiO2 layers from C–V characteristics of MIS structures on Si

This letter investigates the large spread of values of capacitance measured in Si/TiO2 MIS structures for different properties of the TiO2 layer and proposes an approach to understand the behavior of the system. Experimental results show large variations of the maximum capacitance with TiO2 thickness for the as-deposited structures and further highlight the change of trend after annealing. Simulations qualitatively depict the theoretical trends explaining the C–V characteristics to the first order, by the different behaviors of the oxide layer in the structure and the distribution of the majority carriers showing depletion effects

High-performance dual-mode ultra-thin broadband CdS/CIGS heterojunction photodetector on steel

An ultra-thin CdS/CIGS heterojunction photodiode fabricated on steel firstly exhibits dual-mode broadband photodetection from ultraviolet to near infrared spectrum. In the photovoltaic mode, the CIGS photodiode, working as a self-driven photodetector, shows an outstanding photodetection capability (under a light power density of 20 μW cm−2 at 680 nm), reaching a record detectivity of ∼4.4×1012 Jones, a low noise equivalent power (NEP) of 0.16 pW Hz−1/2 and a high Ilight/Idark ratio of ∼103, but a relatively low responsivity of ∼0.39 A W−1 and an external quantum efficiency (EQE) of ∼71%. Working under the same illumination but in the photoconductive mode (1 V reverse bias), the responsivity and EQE are significantly enhanced to 1.24 A W−1 and 226%, respectively, but with a relatively low detectivity of 7×1010 Jones and a higher NEP of 10.1 pW Hz−1/2. To explain these results, a corrected photoconductive gain (G) model indicates that minority electrons could be localized in the defects, surface states and depletion region of the CIGS photodiode, causing excess hole accumulation in the ultra-thin CIGS photodiode and thus high EQE over 100% (G over 1)

High-responsivity broadband photodetection of an ultra-thin In2S3/CIGS heterojunction on steel

Cu(In,Ga)Se2 (CIGS) is a promising light harvesting material for large-area broadband photodetection, but it has been rarely studied up to now. Here an In2S3/CIGS heterojunction photodiode on steel is shown to be highly broadband photo-sensitive, with a photoresponsivity over 0.8 A/W, an external quantum efficiency over 100%, and a detectivity over 8×1010 Jones from 505 to 910nm under a reverse bias of 1 V. Moreover, the CIGS photodiode exhibits an outstanding weak light detection ability (i.e., at light power density of 20µW/cm2), reaching a record responsivity of 2.06 A/W, an impressive EQE of 293%, and a good detectivity of 2.3×1011 Jones at 870 nm under 1 V reverse bias. Importantly, the CIGS photodiode, working as a self-powered photodetector, under 0 V, shows a record detectivity of ∼3.4×1012 Jones with a high responsivity of ∼0.44A/W and a high EQE of ∼63%, at 870 nm

SiOx patterned based substrates implemented in Cu(In,Ga)Se2 ultrathin solar cells: optimum thickness

Interface recombination in sub-μm optoelectronic devices has a major harmful impact in devices performance, showing the need for tailored passivation strategies in order to reach a technological boost. In this work, SiOx based substrates were developed and integrated in ultrathin CIGS solar cells. This study aims at understanding the impact of several SiOx layer thicknesses (3, 8 and 25 nm) when this material is used as a passivation layer. Analysing their electrical parameters, the 8 nm novel SiOx based substrates achieved light to power conversion efficiency values up to 13.2 %, a 1.3 % absolute improvement over the conventional substrate (without SiOx)

Light management design in ultra-thin chalcopyrite photovoltaic devices by employing optical modelling

In ultra-thin chalcopyrite solar cells and photovoltaic modules, efficient light management is required to increase the photocurrent and to gain in conversion efficiency. In this work we employ optical modelling to investigate different optical approaches and quantify their potential improvements in the short-circuit current density of Cu (In, Ga)Se2 (CIGS) devices. For structures with an ultra-thin (500 nm) CIGS absorber, we study the improvements related to the introduction of (i) highly reflective metal back reflectors, (ii) internal nano-textures applied to the substrate and (iii) external micro-textures by using a light management foil. In the analysis we use CIGS devices in a PV module configuration, thus, solar cell structure including encapsulation and front glass. A thin Al2O3 layer was considered in the structure at the rear side of CIGS for passivation and diffusion barrier for metal reflectors. We show that not any individual aforementioned approach is sufficient to compensate for the short circuit drop related to ultra-thin absorber, but a combination of a highly reflective back contact and textures (internal or external) is needed to obtain and also exceed the short-circuit current density of a thick (1800 nm) CIGS absorber

Modelling Supported Design of Light Management Structures in Ultra-Thin Cigs Photovoltaic Devices

Chalcopyrite solar cells exhibit one of the highest conversion efficiencies among thin-film solar cell technologies (> 23.3%), however a considerably thick absorber ≥1.8 μm is required for an efficient absorption of the long-wavelength light and collection of charge carriers. In order to minimize the material consumption and to accelerate the fabrication process, further thinning down of the absorber layer is important. Using a thin absorber layer results in a highly reduced photocurrent density and to compensate for it an effective light management needs to be introduced. Experimentally supported, advanced optical simulations in a PV module configuration, i.e. solar cell structure including the encapsulation and front glass are employed to design solutions to increase the short current density of devices with ultra-thin (500 nm) absorbers. In particular (i) highly reflective metal back reflector (BR), (ii) internal nano-textures and (iii) external textures by applying a light management (LM) foil are investigated by simulations. Experimental verification of simulation results is presented for the external texture case. In the scope of this contribution we show that any individual aforementioned approach is not sufficient to compensate for the short circuit current drop of the thin CIGS, but only a combination of highly reflective back contact and introduction of textures (internal or external) is able to compensate and also to exceed (by more than 5 % for internal texture) photocurrent density of a thick (1800 nm) CIGS absorber

Ultra thin CIGS: 1D/2D modelling methodology and impactful results for cell design

We present the 1 D/ 2 D modelling methodology, using SCAPS and ATLAS software to simulate ultra thin CIGS solar cells, and their impactful results on optical and electrical properties of Al 2 O 3 passivated with point contact structure and unpassivated cells with and without back optical reflector. These simulations help predict optimum conditions compared to different parameters like geometry of contact hole openings ( oxide charges density Qf surface recombination velocity ( and back reflector (BR The impact of the results of these simulations are very significant for cell design and fabrication

Optimization of Back Contact Grid Size in Al2O3-Rear-Passivated Ultrathin CIGS PV Cells by 2-D Simulations

We present a simulation strategy using ATLAS-2D to optimize the back-contact hole grid (i.e., size and pitch of openings) of the Al2O3-rear-passivation layer in ultrathin Cu(In,Ga)Se2 photovoltaic cells.We first discuss and compare our simulation model with a series of experimental nonpassivated and passivated cells to decouple the crucial passivation parameters. The simulation results followthe experimental trends, highlighting the beneficial effects of the passivation on the cell performances. Furthermore, it stresses the influence of the passivation quality at the Al2O3/Cu(In,Ga)Se2 (CIGS) interface and of the contact resistance at the Mo/CIGS interface within the openings. Further simulations quantify significant improvements in short-circuit current and open-circuit voltage for different sizes of openings in the Al2O3 layer, relative to an excellent passivation quality (i.e., high density of negative charges in the passivation layer). However, a degradation is predicted for a poor passivation (i.e., low density of such charges) or a high contact resistance. Consequently, we point out an optimum in efficiency when varying the opening widths at fixed hole-pitch and fixed contact resistance. At equivalent contact resistance, simulations predict that the sizes of the pitch and openings can be increased without optimal performance losses when maintaining a width to pitch ratio around 0.2. This simulation trends have been confirmed by a series of experiments, indicating that it is crucial to care about the dimensions of the opening grid and the contact resistance of passivated cells. These simulation results provide significant insights for optimal cell design and characterizations of passivated UT-CIGS PV cells

SiOx Patterned Based Substrates Implemented in Cu(In,Ga)Se2 Ultrathin Solar Cells: Optimum Thickness

Interface recombination in sub-μm optoelectronics has a major detrimental impact on devices’ performance, showing the need for tailored passivation strategies to reach a technological boost. In this article, SiOx passivation based substrates were de- veloped and integrated into ultrathin Cu(In,Ga)Se2 (CIGS) solar cells. This article aims to understand the impact of a passivation strategy, which uses several SiOx layer thicknesses (3, 8, and 25 nm) integrated into high-performance substrates (HPS). The experimental study is complemented with 3-D lumerical finite-difference time-domain and 2-D Silvaco ATLAS optical and electrical simulations, respectively, to perform a decoupling of optical and electronic gains, allowing for a deep discussion on the impact of the SiOx layer thickness in the CIGS solar cell performance. This article shows that as the passivation layer thickness increases, a rise in parasitic losses is observed. Hence, a balance between beneficial passivation and optical effects with harmful architectural constraints defines a threshold thickness to attain the best solar cell performance. Analyzing their electrical parameters, the 8-nm novel SiOx based substrate achieved a light to power conversion efficiency value of 13.2%, a 1.3% absolute improvement over the conventional Mo substrate (without SiOx)