Quantum Well Solar Cells Research Articles

Efficiency of InN/InGaN/GaN Intermediate-Band Solar Cell under the Effects of Hydrostatic Pressure, In-Compositions, Built-in-Electric Field, Confinement, and Thickness.

This paper presents a thorough numerical investigation focused on optimizing the efficiency of quantum-well intermediate-band solar cells (QW-IBSCs) based on III-nitride materials. The optimization strategy encompasses manipulating confinement potential energy, controlling hydrostatic pressure, adjusting compositions, and varying thickness. The built-in electric fields in (In, Ga)N alloys and heavy-hole levels are considered to enhance the results' accuracy. The finite element method (FEM) and Python 3.8 are employed to numerically solve the Schrödinger equation within the effective mass theory framework. This study reveals that meticulous design can achieve a theoretical photovoltaic efficiency of quantum-well intermediate-band solar cells (QW-IBSCs) that surpasses the Shockley-Queisser limit. Moreover, reducing the thickness of the layers enhances the light-absorbing capacity and, therefore, contributes to efficiency improvement. Additionally, the shape of the confinement potential significantly influences the device's performance. This work is critical for society, as it represents a significant advancement in sustainable energy solutions, holding the promise of enhancing both the efficiency and accessibility of solar power generation. Consequently, this research stands at the forefront of innovation, offering a tangible and impactful contribution toward a greener and more sustainable energy future.

Improvement of radiation resistance of GaInP/GaInAs/Ge triple-junction solar cell with GaInAs/GaAsP quantum wells

Introducing quantum wells (QWs) into a GaAs solar cell can expand its spectral response range to raise the short-circuit current (J sc). GaInP/GaInAs/Ge triple-junction (TJ) solar cells with strain-balanced InGaAs/GaAsP QWs in a GaInAs cell have been fabricated and irradiated by 1 MeV electron fluences. The AM0 efficiency of the TJ cell increases from 30% to 32% by inserting 30 period QWs. Under the electron irradiation condition of 1 MeV, 1 × 1015 cm−2, the radiation resistance of quantum well solar cells (QWSCs) is worse than that of the reference cell without QWs. The effect of QW doping on the radiation resistance of the 30 QWSC has been studied. After irradiation, the radiation resistance of J sc is improved by the unintentional doping of QWs, resulting in lower degradation of efficiency. An efficiency of 26.30% after irradiation is attained and this indicates that the QWSC has expectable potential to be applied to satellites.

Diversity Analysis of Defect Distribution and Carriers Quantization in Cu 2 ZnSnS 4/Cu2ZnSn(S,Se) 4 Kesterite Quantum Well Solar Cell

Kesterite materials, with a major advantage of direct bandgap and earth abundant material,are popular for low cost and thin film solar cell applications. Despite the popularity, the material fails to achieve significant efficiency due to the emergence of defect states during the growth process. In this paper multiple approaches have been investigated focusing on implementation of Quantum Wells(QW) to enhance the performance of solar cell. QW structure are created using CZTS x Se 1−x and Cu 2 ZnSnS 4 as QW and barrier material layers respectively. The performance evaluation of the QW solar cell is also carried out with the presence of most popular donor-like defect states in a gaussian and tail distribution way. The behavior of the device is investigated in presence of broad range of QWs from 2 to 100QWs to ensure the effect of defects on rise in QWs. The worst case performance of the solar cell is obtained to be efficiency of 9.6% under a high level of defect states. A remarkable observation on the effect of increase in number of QWs and defect states on solar cell parameters solar cell are concluded.

Photovoltaics literature survey (No. 181)

Photovoltaics literature survey (No. 181)

Impact of Well Number on High-Efficiency Strain-Balanced Quantum-Well Solar Cells

The addition of lower energy-gap InGaAs quantum wells to the depletion region of GaAs solar cells is an established approach to enhance photovoltaic performance by extending infrared collection. However, maintaining a high open-circuit voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> ) when including quantum wells has proven more challenging. In this article, we report on high-efficiency ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">η</i> > 23.5% AM0) strain-balanced quantum well (SBQW) solar cells with increased current output and efficiency while maintaining the same high open-circuit voltage of baseline devices without quantum wells ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> > 1.02 V). The single-junction GaAs-based device structures discussed herein employ a radiation-tolerant, n-i-p front-junction architecture and include both an InGaP heterojunction (HJ) emitter and in most cases an underlying AlGaAs distributed Bragg reflector. The impact of well number on photovoltaic device characteristics is described using an analytical model that assumes current collection, radiative recombination, and nonradiative recombination all increase with well number and are additive to the baseline cell. The highest <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> and efficiency SBQW devices employ shallow 9.2 nm In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.07</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.93</sub> As quantum wells and 11.5 nm GaAs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.90</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.10</sub> barrier layers to maintain strain balancing. Increasing the indium composition in the wells from 7% to 10% to form deeper wells requires a thicker strain-balancing barrier layer and results in an apparent increase in radiative recombination and decreased <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> . Single-junction high-efficiency SBQW device performance is also demonstrated in thinner base-layer structures with graded HJs—device structures suitable for inclusion in radiation-tolerant multi-junction structures.

Optically thick GaInAs/GaAsP strain-balanced quantum-well tandem solar cells with 29.2% efficiency under the AM0 space spectrum

GaAs is often used as a multijunction subcell due to its high material quality on GaAs substrates, despite having a non-optimal bandgap. The bandgap can be beneficially reduced using many layers of thin, strain-balanced GaInAs in a superlattice or quantum well device, but achieving excellent carrier collection without increased recombination has proven challenging. Here, we develop and demonstrate high performance, optically thick GaInAs/GaAsP strain-balanced solar cells. Excellent material quality is achieved in thick superlattices by using growth conditions that limit progressive thickness and composition fluctuations. Bandgap-voltage offsets as low as 0.31 V are shown in superlattice cells using thin, highly strained GaP barriers. Optically thick superlattice cells with over 2500 nm of total GaInAs in the depletion region are developed, enabling 3.8 mA/cm2 of extra photocurrent beyond the GaAs band edge under the AM0 space spectrum. Optimized superlattice solar cells are incorporated into two-junction devices that achieve 29.2% efficiency under the AM0 space spectrum due to their improved bandgap combination and high subcell voltages.

Exploiting High-Density Earth-Abundant Kesterite Quantum Wells for Next-Generation PV Technology

Quantum engineering in kesterite solar cells reveals a blending advancement keeping in mind that copper zinc tin sulfide (CZTS)-based material requires high-research implementation as a replacement for copper indium gallium selenide (CIGS) materials. In this article, quantum well-solar cells (QWSCs) on kesterite material is proposed in which CZTS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1−<i>x</i></sub> and CZTS material is taken as well and barrier materials with different Sulfur (S) and Selenium (Se) content. All the optical, electrical, and material properties are investigated in detail to achieve high efficiency. The focus on the incorporation of a high number of quantum wells (QWs) (2 to 100 QWs) and performance analysis show the uniqueness of the study. Quantum efficiency (QE) of the solar cell with separate internal and external absorptions is also investigated here. Different issues on carrier propagation, recombination, and collection are emphasized to highlight the effect of carrier quantization in the material. A remarkable efficiency of 38% with 88% fill factor (FF) could be achieved from the broad range of the proposed structure, which may show a new path for next-generation solar cells.

A proposal to enhance SnS solar cell efficiency: the incorporation of SnSSe nanostructures

Tin sulfide (SnS) semiconductor has recently attracted a great deal of attention from the scientific community regarding its application in solar cells. However, SnS solar cell efficiencies are still limited to less than 5%. The incorporation of nanostructures into solar cells has been demonstrated to be a potential route to improve device performance. So far, there have been no reports on the incorporation of nanostructures into SnS solar cells. In this work, a theoretical study on the incorporation of tin sulfide selenide (SnSSe) nanostructures in the form of quantum wells (QWs) into SnS solar cells under the radiative limit is presented, for the first time. In particular, the impact of well number, well thickness, and Se/(S + Se) compositional ratio at the wells, on solar cell characteristics, is evaluated. An efficiency enhancement of 11.1% is found for a SnS/SnSSe QW solar cell, compared to the optimized device without nanostructures, for 50 wells of 54 nm width with a Se/(S + Se) well composition of 0.4 and considering barrier thicknesses of 5 nm, which is a result of the increase in short-circuit current density of 14.5%. The influence of defects at wells and barriers, as well as defects at interfaces, on solar cell behavior is also presented, demonstrating that the introduction of QWs can result in higher efficiencies than that of the device without nanostructures. In this sense, the addition of SnSSe nanostructures to SnS solar cells is introduced as a potential route to promote the absorption of photons with energy lower than the SnS band-gap, while keeping open-circuit voltage values similar to those of a SnS solar cell without nanostructures, thereby increasing solar cell efficiency.

Voltage preserved GaInP single junction solar cell using type-A InP multiple quantum well structure with enhanced efficiency

Two photon absorption phenomenons is used to enhance the short circuit current density (Jsc) in most of the intermediate band solar cell (SC). But, higher recombination in the IB region results in degradation of the open circuit voltage (Voc). Therefore limits the performance of IB cell. A GaInP single junction (SJ) cell is designed with type-A multiple InP quantum well (QW) with proper dimensions in the intrinsic region. The objective of the study is to enhance the Jsc, while preserving the Voc. The type-A QW structure was formed in the quantum region of the cell. The insertion of QWs increases the Jsc, while the proper dimension of the QW layers, helps in voltage preservation. The recombination in the mini-bands of the sequential quantum region exhibits radiative recombination. The long wavelength absorption indicates enhanced quantum efficiency (QE). The designed structure of GaInP based multi QW solar cell shows superior efficiency of 22.41 % and QEs well above 80 %.

Study of hole-blocking and electron-blocking layers in a InaS/GaAs multiple quantum-well solar cell

In this work, a GaAs-based quantum well solar cell with a 25-layer InAs/GaAs intermediate layer is simulated in Silvaco Atlas TCAD software. In order to reduce the recombination caused by the presence of the quantum layers and increase the absorption of photons, electron blocking layers (EBLs) and hole blocking layers (HBLs) have been added to the solar cell in an In0.5(Al0.7Ga0.3)0.5P semiconductor. The results show that the efficiency of the proposed solar cell increases 17.38% by obtaining impurity the thickness and doping of the EBL and HBL layers. It can be concluded that the use of the In0.5(Al0.7Ga 0.3)0.5P semiconductor with EBL and HBL layers decreases the open circuit voltage (Voc) caused in the quantum wells. The efficiency of the proposed solar cell with EBL and HBL layers was found to be 44.65%.

The role of intervalley phonons in hot carrier transfer and extraction in type-II InAs/AlAsSb quantum-well solar cells

Simultaneous continuous wave (CW) photoluminescence and monochromatic current density-voltage (J-V) measurements of InAs/AlAsSb QW p-i-n diodes reveal stable hot carriers observed at relatively low power (nearly independent of power). This behavior is attributed to preferential scattering of high energy carriers to the upper satellite L- and X-valleys, which inhibits carrier thermalization via LO phonon emission. Although both high electric field and optical excitation are shown to enable stable hot carrier generation in the quantum wells (QWs), the extraction of these carriers is inhibited by the mismatch in valley degeneracy (L to Γ) across the InAs QW/n-AlInAs layers resulting in carrier localization in the QWs in the operating regime of the solar cell.

Abnormal staircase-like I-V curve in InGaN quantum well solar cells

InGaN/GaN multiple quantum well-solar cells with different barrier thicknesses have been comparatively studied, and it is demonstrated that a thinner barrier facilitates the transport of photogenerated carriers. Meanwhile, an abnormal but regular staircase-like I-V curve is observed. The induction factors and microscopic physical process relevant to this abnormal feature are analyzed in detail, which is found closely related to the inadequate internal field and special epitaxial structure. Furthermore, the formation conditions of I-V curves with various types of inflections are also proposed. This work provides insight into the origin of device problems, which can be applicable to other types of solar cells.

Tunneling Current of an AlGaAs/GaAs Multiple-Quantum-well Solar Cell Considering a Trapezoidal Potential Barrier

T he barrier created in the intrinsic multiple quantum well (MQW) region of a quantum well solar cell (QWSC) appears to be trapezoidal in nature. In this paper, a trapezoidal barrier has been considered and the expression for the tunneling current of the QWSC has been obtained. The variation of the tunneling current with temperature has been shown graphically. In addition to this, the expressions for temperature and wavelength dependent refractive indices of different regions of the QWSC have been taken into account while performing the calculations of reflection coefficient. Solar cells having different well width and barrier width have been chosen and the variation of the tunneling current densities with wavelength of incident light and temperature of the device has been studied for each cell. It has been observed that the tunneling current density falls with increase in the temperature of the cell.

Semi-polar InGaN/GaN multiple quantum well solar cells with spectral response at up to 560 nm

We demonstrate a series of semi-polar InGaN/GaN multiple quantum well (QW) based solar cells with high indium content, where operating wavelength ranges from green to amber. These devices are grown on high crystal quality overgrown semi-polar GaN templates. The spectral response at a long wavelength of up to 560nm has been obtained. With increasing indium content of QWs (i.e., increasing operating wavelength), the external quantum efficiency increases across a wide range of wavelength. Compared to the device with green QWs, the devices with amber QWs exhibits significantly increased short-circuit current density and conversion efficiency, achieving a current density of 1.4mA/cm2 and an enhancement factor of 170% under the AM 1.5G illumination. Photoluminescence excitation measurements show that it is attributed to enhanced light absorption in InGaN QWs by pushing the QW absorption edge towards longer wavelength. Furthermore, another series of InGaN QW solar cells is investigated with different indium contents in the three QWs of each device. The device with two yellow QWs on the top and one blue QW underneath exhibits spectral response at a long wavelength of up to 560nm, whereas the device with one blue QW on the top and two yellow QWs underneath shows no response beyond 460nm. It reveals that the InGaN QW closest to the top p-type GaN plays a determined role in the spectral response on the long wavelength side.

Modeling and simulation of solar cells quantum well based on SiGe/Si

In recent years, the development of quantum well solar cells QWSCs (Quantum Well Solar Cells) has generated a great deal of interest. These configurations have shown good promise to optimize the low conversion efficiency of conventional solar cells because of the high rate of absorption losses present in them. In this work, we are interested in modeling and simulation of two different structures of solar cells, a simple solar cell based on silicon Si and a quantum well solar cell SiGe/Si. When a solar cell is compared to 80 quantum well layers of Si0.8Ge0.2with a pin solar cell based on Si. The short circuit current Jsc increases from 23.55 to 37.48 mA/cm2 with a relative increase of 59.15% found. In addition, the limit of the absorption band of the lower energy photons extends from 1100 nm to 2000 nm.

Modeling Si/SiGe/Si Quantum Well Solar Cell Using Different Well Width and Mole Fraction

&lt;p&gt;Quantum Well Solar Cell ( QWSC) was proposed as a means to achieve higher efficiencies compare with conventional monolithic solar cell structures. Quantum well formed by adding lower band gap material within intrinsic region of p-i-n solar cell with less than 100 A thicknesses. In this research, five structure of QWSC device were designed with different quantum well thickness. Each structure using different SiGe mole fraction in order to achieve the influence of mole fraction variation to quantum efficiency (QE). Parameters of SiGe in simulations were obtained from various references to use with PC1D and Simwin Software. From simulation result, quantum efficiency will increase from mole fraction 0.2 (84.5135 %) until reaching maximum efficiency at mole fraction 0.75 (91.5703 %). Quantum efficiency begin to decrease at mole fraction higher than 0.75. At mole fraction 0.85 quantum efficiency equal to 90.4830 % and at mole fraction 0.95 quantum efficiency sharply become 71.6327 %.&lt;/p&gt;

Efficiency improvement of quantum well solar cell with the AuGeNi metallization and Si3N4 ARC design

This study demonstrates the power conversion efficiency enhancement on In0.19Ga0.81As/GaAs quantum well solar cells (QWSC). The solar cell structure was grown on n-type (100)-oriented GaAs substrate by using solid-source molecular beam epitaxy technique and divided into square pieces. In order to understand whether the eight quantum wells were grown or not, scanning electron microscopy (SEM), and secondary ion mass spectrometry characterizations were done at room temperature. After that, the Si3N4 antireflection layers were coated onto both two square pieces of In0.19Ga0.81As/GaAs QWSC structure and p-GaAs substrate at different temperatures by the radio frequency magnetron sputtering system. The optical properties of the Si3N4 coated and uncoated p-GaAs samples have been evaluated by means of ultraviolet-visible spectrometry measurements at room temperature. According to ultraviolet-visible spectrometry results, the best Si3N4 antireflection coated one was obtained at 100 °C substrate temperature. Thus, the In0.19Ga0.81As/GaAs QWSC structure with and without Si3N4 layer, which was coated at 100 °C substrate temperature, was selected for other measurements and processes. Moreover, the In0.19Ga0.81As/GaAs QWSC samples with and without Si3N4 antireflection coating were separately fabricated with different metallization materials for obtaining the solar cell electrical output parameters. AuGe and AuGeNi metallization materials were used for the fabrication processes. After fabrication, the electrical output parameters were extracted from the current-voltage measurements at room temperature both in dark and under AM1.5 – 1 Sun illumination. The proposed design which includes the AuGeNi metallization and Si3N4 antireflection layer enhanced the power conversion efficiency by 44.40%.

Impact of alloyed capping layers on the performance of InAs quantum dot solar cells

The impact of using thin GaAs(Sb)(N) capping layers (CLs) on InAs/GaAs quantum dots (QDs) is investigated for their application in solar cell devices. We demonstrate the ability to combine strain-balancing techniques with band engineering approaches through the application of such CLs. Extended photoresponse is attainable by means of an independent tunability of the electron and hole confinements in the QD. Moreover, the CL acts itself as a quantum well (QW), providing an additional photoresponse, so that the devices work as hybrid QD–QW solar cells. The use of a GaAsSb CL is particularly beneficial, providing devices with efficiencies under AM1.5 conditions 20% higher than standard GaAs-capped QDs. This is mainly due to a significant increase in photocurrent beyond the GaAs bandgap, leading to an enhanced short-circuit current density (Jsc). The addition of N to the CLs, however, produces a strong reduction in Jsc. This is found to be related to carrier collection problems, namely, hindered electron extraction and retrapping in the CLs. Nevertheless, the application of reverse biases induces a release of the trapped carriers assisted by a sequential tunneling mechanism. In the case of GaAsN CLs, this leads to a complete carrier collection and reveals an even higher QD–QW-related photocurrent than when using a GaAsSb CL. The hindered carrier collection is stronger in the case of the quaternary CLs, likely due to the faster recombination rates in the type-I GaAsSbN/GaAs QW structure as compared to the type-II ternary counterparts. Nevertheless, alternative approaches, such as the use of a thinner CL or a short-period superlattice CL, lead to significant improvements, demonstrating a great potential for the quaternary CLs under a proper device design.

Submonolayer InGaAs/GaAs quantum dot solar cells

Optical and structural properties of submonolayer InGaAs/GaAs quantum dot solar cells (SML-QDSCs) are investigated and compared with quantum well solar cells (QWSCs). Compared with InGaAs/GaAs QWSCs with a similar structure, the material quality for SML QDSCs is significantly improved with a reduced density of both crosshatch patterns and defects. This coincides with a much higher photoluminescence intensity obtained for SML QDSCs. SML QDSCs thus exhibit an increase in open circuit voltage of 70meV and an improvement in short circuit current from 15.9mA/cm2 to 17.7mA/cm2 in comparison with QWSCs. These findings present a promising alternative to quantum wells in photovoltaic applications.

GaAs/AlGaAs quantum wells with indirect-gap AlGaAs barriers for solar cell applications

We have fabricated GaAs/AlGaAs quantum well (QW) solar cells in which 3 nm-thick QWs and indirect-gap Al0.78Ga0.22As barriers are embedded, and we studied extraction processes of photogenerated carriers in this QW system. The photocurrent under 700 nm light illumination at voltages close to the open-circuit voltage shows only a small reduction, indicating that the carrier recombination inside QWs is largely suppressed. We attribute this result to an efficient extraction of electrons from the QWs through the X-valley of AlGaAs. The insertion of QWs is shown to be effective in extending the absorption wavelengths and in enhancing the photocurrent. The use of indirect-gap materials as barriers is found to enhance carrier extraction processes, and result in an improved performance of QW solar cells.