An expedient semi-empirical modelling approach for optimal bandgap profiling of stoichiometric absorbers: A case study of thin film amorphous silicon germanium for use in multijunction photovoltaic devices

Vrijer, Thierry de; Parasramka, Harsh; Roerink, Steven J.; Smets, Arno H. M.

doi:10.1016/j.solmat.2021.111051

Cited by 8 publications

(12 citation statements)

References 35 publications

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Section: Why Different Group IV Alloyssupporting

confidence: 85%

“…Considering group IV elements, it can be observed that the bandgap energy of SiC > Si > SiGe > Ge > GeCSn. Similar, more detailed, observations have been reported before in relation of the stoichiometry of two-element group IV alloys such as SiGe:H [27,30,31] and SiC:H. [32,33] The second set, trendlines II, indicate a change in the n @600nm and E 04 as a function of void fraction, or porosity. In these hydrogenated amorphous (a-) materials, nano-sized voids are present in the material at sites where multiple C, Si or Ge atoms are missing.…”

Section: Why Different Group IV Alloyssupporting

confidence: 83%

“…As these two conditions are not indicative of a dense film, and P RF is, the relevant mechanism in this range is likely energetic ion-bombardment. The processing of dense films under lowenergetic ion-bombardment conditions is not in line with earlier reports on Ge:H [44] and SiGe:H [27] films, where the beneficial effect ion-bombardment induced densification was reported.…”

Section: The Right Processing Windowsupporting

confidence: 56%

“…In this section, the high level relations between the structural and opto-electrical characteristics are addressed. For the films presented in Figure 2 more information about the relation between the processing conditions and structural characteristics, as well as more detailed structural investigation of the films, is provided for GeCSn, [20] Ge, [22,[24][25][26] SiGe, [22,27] SiO. [24] From these collective works, three structural characteristics through which a change in density can be realized.…”

Section: Why Different Group IV Alloysmentioning

confidence: 99%

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Opto‐Electrical Properties of Group IV Alloys: The Inherent Challenges of Processing Hydrogenated Germanium

et al. 2022

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In this paper the opto-electrical nature of hydrogenated group IV alloys with optical bandgap energies ranging from 1.0 eV up to 2.3 eV are studied. The fundamental physical principles that determine the relation between the bandgap and the structural characteristics such as material density, elemental composition, void fraction and crystalline phase fraction are revealed. Next, the fundamental physical principles that determine the relation between the bandgap and electrical properties such as the dark conductivity, activation energy, and photoresponse are discussed. The unique wide range of IV valence alloys helps to understand the nature of amorphous (a-) and nanocrystalline (nc-) hydrogenated (:H) germanium films with respect to the intrinsicity, chemical stability, and photoresponse. These insights resulted in the discovery of i) a processing window that results in chemically stable Ge:H films with the lowest reported dark conductivity values down to 4.6•10 -4 (𝛀 •cm) -1 for chemical vapor deposited Ge:H films, and ii) O, C and Sn alloying approaches to improve the photoresponse and chemical stability of the a/nc-Ge:H alloys.

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Section: Why Different Group IV Alloyssupporting

confidence: 85%

Section: Why Different Group IV Alloyssupporting

confidence: 83%

Section: The Right Processing Windowsupporting

confidence: 56%

Section: Why Different Group IV Alloysmentioning

confidence: 99%

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Opto‐Electrical Properties of Group IV Alloys: The Inherent Challenges of Processing Hydrogenated Germanium

et al. 2022

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“…For the initial 12 nm of SiO X growth, the diborane gas flow rate is set at 10 sccm 0.02% B 2 H 6 in H 2 , which is increased to 50 sccm for the final 4 nm. The other p-layer deposition conditions are similar to those reported in [15]. Following deposition of the photoactive stack, a 70 nm indium-doped tin-oxide (ITO) is sputtered and a 500 nm Al metal front grid is evaporated.…”

Section: Methodsmentioning

confidence: 99%

The optical performance of random and periodic textured mono crystalline silicon surfaces for photovoltaic applications

et al. 2022

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Surface textures that result in high optical yields are crucial for high efficiency photovoltaic (PV) devices. In this work three different texturing approaches are presented that result in smooth concave structures devoid of sharp features. Such features can sustain the crack-free growth of device quality nano- to poly-crystalline materials such as nano-crystalline silicon, perovskites or C(I)GS, facilitating routes towards hybrid multijunction PV devices. A sacrificial implanted poly-c-Si layer is used to develop a random surface texture for the first texturing approach (Tsac). The influence of the processing conditions, such as layer thickness, implantation energy, dose and ion type, annealing time and temperature, of the sacrificial layer on the developed surface features is investigated. Additionally, a photolithographically developed honeycomb texture (Thoney) is presented. The influence of mask design on the honeycomb features is discussed and a relation is established between the honeycomb period and crack formation in nano-crystalline silicon layers. The reflective properties (spectral reflection, haze in reflection and angular intensity distribution) of these approaches are characterized and compared to a third texturing approach, Tsp, the result of chemically smoothened pyramidal <111> features. It was demonstrated that high optical scattering yields can be achieved for both Thoney and Tsp. Additionally, the performance of a-Si/nc-Si tandem devices processed onto the different textures is compared using both optical device simulations and real device measurements. Simulations demonstrate strong improvements in Jsc-sum (≈45%), in reference to a flat surface, and high Voc*FF of over 1 V are demonstrated for Tsp.

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Application of metal, metal‐oxide, and silicon‐oxide based intermediate reflective layers for current matching in autonomous high‐voltage multijunction photovoltaic devices

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Miedema

Blackstone

et al. 2022

Progress in Photovoltaics

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A logical next step for achieving a cost price reduction per Watt peak of photovoltaics (PV) is multijunction PV devices. In two-terminal multijunction PV devices, the photo-current generated in each subcell should be matched. Intermediate reflective layers (IRLs) are widely employed in multijunction devices to increase reflection at the interface between subcells to enhance current generation in the subcell(s) positioned before the IRL, in reference to the incident light. In this work, the results of over 65 multijunction devices are presented, in order to explore the effect of different current matching approaches. The influence of variations in absorber thickness as well as thickness variations of different IRLs based on silicon-oxide, various transparent conductive oxides (TCO), and metallic layers on all-silicon multijunction PV devices is studied. Specifically, hybrid, 2-terminal, monolithically integrated silicon heterojunction (SHJ) and thin film nanocrystalline silicon (nc-Si:H) and amorphous silicon (a-Si:H) tandem and triple junction devices are processed. Based on these experiments, certain design rules for optimal current matching operation in multijunction devices are formulated. Finally, taking these design rules into account, record allsilicon multijunction devices are processed. Conversion efficiencies close 15% and V oc ≈ 2 V are demonstrated for triple junction SHJ/nc-Si:H/a-Si:H devices. Such conversion efficiencies for a wireless, high-voltage wafer-based all-silicon 2-terminal multijunction PV device opens the way for efficient autonomous solar-to-fuel synthesis systems as well as other wireless innovative approaches in which the multijunction solar cell is used not only as a photovoltaic current-voltage generator, but also as an ion-exchange membrane, electrochemical catalysts, and/or optical transmittance filter.

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An expedient semi-empirical modelling approach for optimal bandgap profiling of stoichiometric absorbers: A case study of thin film amorphous silicon germanium for use in multijunction photovoltaic devices

Cited by 8 publications

References 35 publications

Opto‐Electrical Properties of Group IV Alloys: The Inherent Challenges of Processing Hydrogenated Germanium

Opto‐Electrical Properties of Group IV Alloys: The Inherent Challenges of Processing Hydrogenated Germanium

The optical performance of random and periodic textured mono crystalline silicon surfaces for photovoltaic applications

Application of metal, metal‐oxide, and silicon‐oxide based intermediate reflective layers for current matching in autonomous high‐voltage multijunction photovoltaic devices

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