Quantum confinement-tunable solar cell based on ultrathin amorphous germanium

Meddeb, Hosni; Osterthun, Norbert; Götz, Maximilian; Sergeev, Oleg; Gehrke, Kai; Vehse, Martin; Agert, Carsten

doi:10.1016/j.nanoen.2020.105048

Cited by 25 publications

(25 citation statements)

References 124 publications

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“…[260] An exciting example for the significant impact of QC-tunable bandgap was proposed by Meddeb et al, who realized a proof-of-concept for one of thinnest QWSC device using a hydrogenated amorphous silicon/germanium materials system (Figure 4e). [235] When the thickness of the a-Ge:H nanoabsorber was reduced from 20 nm down below 2 nm, an upward shift of the conduction band occurred, resulting in a bandgap tuning from below 1 eV up to 1.56 eV. This leads to a trade-off between different PV characteristics, while maintaining a comparable power conversion level (PCE ≈ 4%).…”

Section: Bandgap Tuning In Single Junction Sc Technologiesmentioning

confidence: 99%

See 1 more Smart Citation

Tunable Photovoltaics: Adapting Solar Cell Technologies to Versatile Applications

Meddeb

Götz‐Köhler

Neugebohrn

et al. 2022

Advanced Energy Materials

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solar, wind, hydro, geothermal, and biomass, to enable a steady mitigation of greenhouse gas emissions, which are causing the planetary climate change and global warming. [5][6][7] Additionally, due to the economic development and the worldwide urbanization, a continuous rise of the global energy consumption across all key sectors, that is, power, heating, industry, and transport is occurring. This is expressed by an increase in the annual global electricity demand by 4.5% in 2021 corresponding to additional 1000 TWh. [4] Hence, strict criteria for the selection of competitive and abundant energy alternatives are imposed, requiring high yield at affordable prices. [8] The share of total renewables power generation excluding hydropower exceeded 3000 TWh in 2020, corresponding to almost 12% of the global electricity generation. [3] Considering an effective synergy between various sustainable energy candidates, solar photovoltaics (PV) have demonstrated great capabilities that can satisfy the requirements in the pathway towards 100% renewable electricity. [9][10][11][12] Owing to the research and development activities over the last decades, the power conversion efficiencies of solar cells (SC) have skyrocketed with a prolonged operation lifetime (>15 years) and a drastic plummeting in manufacturing costs (global average module selling price below $0.25 per W). [6,[13][14][15] The rapid universal deployment of PV resulted in a contribution of about 3.4% in the worldwide electricity generation in 2020. [3] Presently, the global installed PV capacity is approaching 1 TW and it is envisioned to reach ≈10 TW by 2030 and 30 to 70 TW by 2050. [16] Interestingly, along with massive electricity production using conventional solar power plants and rooftop solar panels, ancillary concepts of PV offer new strategies for supplying modern systems in versatile applications. [17][18][19] Moreover, diverse functionalities beyond solar energy harvesting can be afforded by adaptive PV, including aesthetic appearance, visual comfort and thermal management. [17,18,20,21] The distributed nature and the ubiquitous accessibility of multifunctional PV products are substantial features of solar PV in contrast to other renewable energies. However, traditional SCs dominating the market impose intrinsic optoelectronic and thermomechanical limitations, that prohibit their multifunctional utilization. To overcome these drawbacks, novel functional materials and innovative device architecture Solar photovoltaics (PV) offer viable and sustainable solutions to satisfy the growing energy demand and to meet the pressing climate targets. The deployment of conventional PV technologies is one of the major contributors of the ongoing energy transition in electricity power sector. However, the diversity of PV paradigms can open different opportunities for supplying modern systems in a wide range of terrestrial, marine, and aerospace applications. Such ubiquitous and versatile applications necessitate the development of PV technologies with customized desig...

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Section: Bandgap Tuning In Single Junction Sc Technologiesmentioning

confidence: 99%

Section: State Of the Art Of Tunable Solar Cell Technologiesmentioning

confidence: 99%

Tunable Photovoltaics: Adapting Solar Cell Technologies to Versatile Applications

Meddeb

Götz‐Köhler

Neugebohrn

et al. 2022

Advanced Energy Materials

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“…Interestingly, the large Bohr radius of ≈24 nm for germanium enables quantum‐size effects for absorber thicknesses below this range. [ 8–11 ] This leads to a widening of the a‐Ge:H quantum well bandgap of the nanoabsorber from 0.98 eV for 20 nm to 1.56 eV for 2 nm and allows a major increase in the open‐circuit voltage and fill factor. [ 8 ]…”

Section: Introductionmentioning

confidence: 99%

Titanium‐Oxide‐Based Electron‐Selective Contact for Ultrathin Germanium Quantum Well Solar Cell

Osterthun

Meddeb

Berends

et al. 2022

Physica Status Solidi (a)

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In solar cells with an optical cavity as a light trapping mechanism, parasitic absorption is among the main detrimental optical losses. One approach to reducing these losses is the implementation of charge carrier‐selective contacts with wide bandgaps using thin metal oxides like titanium oxide (TiOx). Herein, it is proved that TiOx is a suitable alternative for lossy n‐doped hydrogenated amorphous silicon (n a‐Si:H) as electron selective contact in ultrathin solar cells based on intrinsic hydrogenated amorphous germanium (a‐Ge:H). The integration of the TiOx layer leads to an improved photocurrent generation in the blue light wavelengths. Furthermore, a substantial extraction of charge carriers is demonstrated from the a‐Ge:H quantum well nanoabsorber embedded between intrinsic a‐Si barrier layers. However, the substitution of n a‐Si:H by TiOx results in limited photovoltaic performance due to a lower open‐circuit voltage. This effect is analyzed via electrical simulation considering a variation in the electron affinity and the doping of TiOx as well as the defect density in the silicon buffer. Moreover, the TiOx‐based solar cell exhibits improved light transmittance when the opaque back contact is omitted, which is beneficial for semi‐transparent applications.

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“…[3][4][5][6][7][8][9][10][11] Among these diverse PV materials, QDs possess unique nanostructural uniformity and highly tunable features, including quantum confinement effects and multiple exciton generation (MEG). [12][13][14][15][16][17] QD solar cells can be fabricated as semitransparent and flexible for promising applications, such as, wearable energy collectors and building-integrated photovoltaics. [18,19] QDs are defined as nanometer-sized semiconducting crystals, usually chemically synthesized with surface ligands.…”

mentioning

confidence: 99%

Quantum Dots for Photovoltaics: A Tale of Two Materials

Duan

Guan

et al. 2021

Advanced Energy Materials

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solar cells (PSCs), and colloidal quantum dots (QDs) solar cells, have been quickly developed. [3][4][5][6][7][8][9][10][11] Among these diverse PV materials, QDs possess unique nanostructural uniformity and highly tunable features, including quantum confinement effects and multiple exciton generation (MEG). [12][13][14][15][16][17] QD solar cells can be fabricated as semitransparent and flexible for promising applications, such as, wearable energy collectors and building-integrated photovoltaics. [18,19] QDs are defined as nanometer-sized semiconducting crystals, usually chemically synthesized with surface ligands. [20,21] When the size of a semiconducting crystal reduces to the molecular scale, its bulk properties alter simultaneously. [22,23] Owing to the quantum confinement effect, the absorption spectra and energy levels of QDs can be easily tuned by size variation. For example, the bandgap of cadmium telluride (CdTe) bulk material is around 1.48 eV, while the bandgap of the CdTe QD can be tuned from 2.06 to 2.32 eV by a slight size reduction from 2.47 to 2.10 nm. [24,25] The quantum confinement effect also allows better energy level and absorption matching for QD-based optoelectronic devices such as photodetectors, light-emitting diodes, and solar cells. [26][27][28][29][30][31][32][33][34] Additionally, QDs enable hot cattier extraction due to the MEG effect, where one absorbed photon with high energy may generate two or more excitons. [27,35,36] The unique capability of MEG in QD solar cells can potentially improve the power conversion efficiency (PCE) of single-junction devices and thus overcome the Shockley-Queisser (SQ) PCE limit. [37][38][39] In the past decades, increasing research attention has been paid to QD solar cells, and many materials have been exploited in this context. Although there have been some trials on leadfree materials, such as Indium arsenide (InAs), InP, and AgBiS 2 , their device performances are still poor, with PCE less than 6%. [40][41][42][43][44][45] Up to now, most of the high-performance devices were reported from lead-based QDs in two main categories: lead chalcogenides (PbX, X = S, Se) and lead halide perovskites (PVK). Figure 1a depicts the progress in PCE values and accumulated publication numbers of lead-based QD solar cells, shown as points and columns, respectively, since 2010. With recent progress in device structure design, band-alignment engineering, and optimized surface passivation, the PCE of QD solar cells has constantly increased, achieving a record of 16.6% to date. [46][47][48] Before 2016, QD solar cells were mainly composed of PbX (X = S, Se), and continuous efforts have recently culminated in a remarkable PCE of 13.8%. [53][54][55] PbX usually crystallizes in a cubic structure with S or Se atoms located at octahedral Quantum dot (QD) solar cells, benefiting from unique quantum confinement effects and multiple exciton generation, have attracted great research attention in the past decades. Before 2016, research efforts were mainly devoted to solar cells ...

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Quantum confinement-tunable solar cell based on ultrathin amorphous germanium

Cited by 25 publications

References 124 publications

Tunable Photovoltaics: Adapting Solar Cell Technologies to Versatile Applications

Tunable Photovoltaics: Adapting Solar Cell Technologies to Versatile Applications

Titanium‐Oxide‐Based Electron‐Selective Contact for Ultrathin Germanium Quantum Well Solar Cell

Quantum Dots for Photovoltaics: A Tale of Two Materials

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