Quantum Dot Solar Cells Research Articles

Temperature dependence photoreflectance spectroscopy of InAs/GaAs quantum dot solar cell with AlGaAs potential barrier

Temperature dependence photoreflectance spectroscopy of InAs/GaAs quantum dot solar cell with AlGaAs potential barrier

In Situ Surface Reconstruction toward Planar Heterojunction for Efficient and Stable FAPbI3 Quantum Dot Solar Cells.

Pure-phase α-FAPbI3 quantum dots (QDs) are the focus of an increasing interest in photovoltaics due to their superior ambient stability, large absorption coefficient, and long charge-carrier lifetime. However, the trap states induced by the ligand-exchange process limit the photovoltaic performances. Here, a simple post treatment using methylamine thiocyanate is developed to reconstruct the FAPbI3 -QD film surface, in which a MAPbI3 capping layer with a thickness of 6.2 nm is formed on the film top. This planar perovskite heterojunction leads to a reduced density of trap-states, a decreased band gap, and a facilitated charge carrier transport. As a result, a record high power conversion efficiency (PCE) of 16.23% with negligible hysteresis is achieved for the FAPbI3 QD solar cell, and it retains over 90% of the initial PCE after being stored in ambient environment for 1000 h.

High‐Efficiency Infrared Sulfide Lead Quantum Dot Solar Cells via Mixed Halide Ions Ligand Engineering

Tandem solar cells are regarded as an effective way to break through the theoretical efficiency of the Shockley–Queisser limit, and large‐size lead sulfide quantum dots (PbS QDs) are considered ideal infrared (IR) photovoltaic materials for absorbing low‐energy IR photons in the bottom subcells of tandem solar cells due to their tunable bandgaps and multiexciton generation effects. However, the exposed (100) surface of large‐size PbS QDs leads to poor passivation during the ligand‐exchange process, resulting in degraded device performance. Herein, a mixed halide ions ligand passivation strategy is developed to synergistically passivate the (111) and (100) facets of large‐size QDs. Particularly, a gradual dropwise addition of lead chloride salts dissolved in dimethyl sulfoxide for achieving precisely proportional surface passivation of Cl ions in the ligand exchange is proposed, which enhances the quality of the QD solids and obtains excellent control of the surface trap states. Additionally, optical and electrical characterization results show that the passivated IR PbS QD solids have higher carrier mobility, longer carrier lifetime, and lower defect density, which increases the IR efficiency of IR PbS QD solar cells to 1.25%.

Stepwise−Process−Controlled Ligand Management Strategy for Efficient and Stable Perovskite Quantum Dot Solar Cells

CsPbI3 perovskite quantum dots (QDs) have attracted much attention in the field of solar cells because of their excellent photovoltaic properties. Conventional modification of long−chain insulating ligands can ensure good dispersion and film−forming stability of QDs, but the limitations of their low defect passivation ability and poor charge transport ability will make them fail to achieve high efficiency in the corresponding solar cell devices. In this study, by introducing “Benzylphosphonic acid” short−chain ligands to the surface of CsPbI3 QDs, the ligands were re−administered on the surface during the preparation of the CsPbI3 QDs as well as during the film−forming process. The strong coordination ability of Benzenephosphonic acid can effectively passivate defects on the surface of CsPbI3 QDs and inhibit non−radiative recombination and phase transition. Meanwhile, this short−chain ligand can effectively promote the charge exchange between adjacent QDs and improve the electrical transport properties of the film. The efficiency of the Benzylphosphonic acid−modified CsPbI3 QDs solar cell reaches 13.91% compared to the unmodified device (PCE of 11.4%). The storage stability and operation stability of the device are also significantly improved. (The efficiency remains at 91% of the original for 800 h of atmospheric storage; the efficiency remains at 92% of the original for 200 h of continuous light exposure.) The present strategy realizes the simultaneous improvement of photovoltaic properties and stability of CsPbI3 QD solar cells and also provides a reference for surface ligand engineering to realize highly efficient and stable perovskite quantum dot solar cells.

Recent Research on Indium-Gallium-Nitride-Based Light-Emitting Diodes: Growth Conditions and External Quantum Efficiency

The optimization of the synthesis of III-V compounds is a crucial subject in enhancing the external quantum efficiency of blue LEDs, laser diodes, quantum-dot solar cells, and other devices. There are several challenges in growing high-quality InGaN materials, including the lattice mismatch between GaN and InGaN causing stress and piezoelectric polarization, the relatively high vapor pressure of InN compared to GaN, and the low level of incorporation of indium in InGaN materials. Furthermore, carrier delocalization, Shockley–Read–Hall recombination, auger recombination, and electron leakage in InGaN light-emitting diodes (LEDs) are the main contributors to efficiency droop. The synthesis of high-quality III-V compounds can be achieved by optimizing growth parameters such as temperature, V/III ratios, growth rate, and pressure. By reducing the ammonia flow from 200 sccm to 50 sccm, increasing the growth rate from 0.1 to 1 m/h, and lowering the growth pressure from 250 to 150 Torr, the external quantum efficiency of III-V compounds can be improved at growth temperatures ranging from 800 °C to 500 °C. It is crucial to optimize the growth conditions to achieve high-quality materials. In addition, novel approaches such as adopting a microrod crystal structure, utilizing the piezo-phototronic effect, and depositing AlN/Al2O3 on top of the P-GaN and the electron-blocking layer can also contribute to improving the external quantum efficiency. The deposition of a multifunctional ultrathin layers of AlN/Al2O3 on top of the P-GaN can enhance the peak external quantum efficiency of InGaN blue LEDs by 29%, while the piezo-phototronic effect induced by a tensile strain of 2.04% results in a 183% increase in the relative electroluminescence intensity of the LEDs. This paper also discusses conventional and inverted p-i-n junction structures of LEDs.

The General Properties of Solar Cells Generations -Quantum Dot as Study Case

Quantum dot solar cells are an important class of solar cells of the third generation because of their optoelectronic characteristics suitable for photovoltaic response because of quantum confinement effect. Quantum dot structured materials are characterized by having a tunable bandgap as a result of a size change in addition to create an intermediate band. Thus, the quantum dots more thoroughly absorb the sun spectrum, and as a result, the solar cell's effectiveness is increased. Quantum dot solar cells' importance lies in increasing the efficiency through an increase in the generation of electron-hole pairs as a result of a single photon being absorbed, in other words several exciton generations. In this review, the generations of solar cells, the existing types and the materials used in each generation will be discussed, as a result of a single additionally to the qualities of quantum dot solar cells and the materials of this type.

A Dual-Polythiophene Blending Strategy to Reduce the Efficiency-Stability-Cost Gap of Solar Cells.

Benefiting from the photovoltaic material innovation and delicate device optimization, high-efficiency solar cells employing polymeric materials are thriving. Reducing the gap of cost, efficiency, and stability is the critical challenge faced by the emerging solar cells such as organics, quantum dots and perovskites. Poly(3-alkylthiophene) demonstrates great potential in organic solar cells and quantum dot solar cells as the active layer or the hole transport layer due to its large scalability, excellent photoelectric performance, and favorable hydrophobicity. The present low efficiency and insufficient stability, restrict its commercial application. In this work, a facile strategy of blending two simple polythiophenes is put forward to manipulate the film microstructure and enhance the device efficiency and thermal stability of solar cells. The introduction of P3PT can improve the power conversion efficiency (PCE) of a benchmark cost-effective blend P3HT:O-IDTBR to 7.41%, and the developed ternary solar cells also exhibit increased thermal stability. More strikingly, the quantum dot solar cells with the dual-polythiophene hole transport layer achieve the highest PCE of 10.51%, which is among the topmost efficiencies for quantum dots/polythiophene solar cells. Together, this work provides an effective route to simultaneously optimize the device efficiency and thermal stability of solar cells.

Photovoltaic performance enhancement on carbon counter electrode based PbS colloidal quantum dots solar cells with surface trap passivation via post-treatment process

Photovoltaic performance enhancement on carbon counter electrode based PbS colloidal quantum dots solar cells with surface trap passivation via post-treatment process

Stable PbS colloidal quantum dot inks enable blade-coating infrared solar cells

Infrared solar cells are more effective than normal bandgap solar cells at reducing the spectral loss in the near-infrared region, thus also at broadening the absorption spectra and improving power conversion efficiency. PbS colloidal quantum dots (QDs) with tunable bandgap are ideal infrared photovoltaic materials. However, QD solar cell production suffers from small-area-based spin-coating fabrication methods and unstable QD ink. Herein, the QD ink stability mechanism was fully investigated according to Lewis acid–base theory and colloid stability theory. We further studied a mixed solvent system using dimethylformamide and butylamine, compatible with the scalable manufacture of method-blade coating. Based on the ink system, 100 cm2 of uniform and dense near-infrared PbS QDs (~ 0.96 eV) film was successfully prepared by blade coating. The average efficiencies of above absorber-based devices reached 11.14% under AM1.5G illumination, and the 800 nm-filtered efficiency achieved 4.28%. Both were the top values among blade coating method based devices. The newly developed ink showed excellent stability, and the device performance based on the ink stored for 7 h was similar to that of fresh ink. The matched solvent system for stable PbS QD ink represents a crucial step toward large area blade coating photoelectric devices.Graphical

A critical perspective for emerging ultra-thin solar cells with ultra-high power-per-weight outputs

Ultrathin, solution-processed emerging solar cells with high power-per-weight (PPW) outputs demonstrate unique potential for applications where low weight, high power output, and flexibility are indispensable. The following perspective explores the literature of emerging PVs and highlights the maximum reported PPW values of perovskite solar cells (PSCs) 29.4 W/g, organic solar cells (OSCs) 32.07 W/g, and quantum dot solar cells 15.02 W/g, respectively. The record PPW values of OSCs and PSCs are approximately one order of magnitude higher compared to their inorganic ultrathin solar cells counterparts (approximately 3.2 W/g for CIGS and a-Si). This consists emerging PVs, very attractive for a variety of applications where the PPW is the key parameter. In particular, both OSCs and PSCs can be implemented in different scenarios of applications (indoor and biocompatible applications for OSCs and outdoor and high-energy radiation conversion conditions for the PSCs) due to their unique optoelectronic and physiochemical properties. Finally, our theoretical optical and electrical simulation and optimization study for the most promising and well-suited PV technologies showed an impressive maximum realistic theoretical PPW limit of 74.3 and 93.7 W/g for PSCs and OSCs, respectively. Our finding in the theoretical section shows that the experimental results achieved in the literature of PSCs and OSCs toward high PPW outputs is not quite close to the theoretical maximum (35% and 40% of the theoretical maximum for OSCs and PSCs, respectively), and thus, more work needs to be done to further increase the experimental PPW output of these promising PV technologies.

Attaining above 30% efficiency of PbS-based colloidal quantum dot solar cell using MoO3 and SnO2 as charge transport layers: a numerical approach

Attaining above 30% efficiency of PbS-based colloidal quantum dot solar cell using MoO3 and SnO2 as charge transport layers: a numerical approach

Ligand‐Mediated Homojunction Structure for High‐Efficiency FAPbI3 Quantum Dot Solar Cells

AbstractFormamidinium lead iodide quantum dots (QDs) show great potential for solar cell applications but suffer from restricted charge transfer due to the insulating nature of their ligand shell. Management of the surface properties and resultant energy band alignment is the key to efficient and stable QD solar cells. Herein, an advance in QD surface passivation by introducing tailored multifunctional ligands (glycocyamine (GLA)) to the FAPbI3 QD surface is demonstrated. The incorporation of GLA ligands can partly substitute the native long‐chain insulating ligands and effectively reduce the non‐radiative recombination loss induced by surface trap states. Notably, the introduction of GLA ligands beneficially shifts the band offsets of the QD films and generates a homojunction structure with a cascading energy band alignment in the QD layers, promoting favorable charge transport and boosting the device's performance. As a result, a record‐high power conversion efficiency (PCE) of 15.34% with improved open‐circuit voltage and fill factor is achieved. Moreover, the GLA‐assisted surface passivation boosts the device stability, in which over 80% and 75% of the original PCEs are maintained after storing the devices for 5500 h in ambient air and 768 h under continuous 1‐sun illumination, respectively.

Enhancing the performance of quantum dot solar cells through halogen adatoms on carboxyl edge-functionalized graphene quantum dots

This research has been conducted to find new, high-performing, safe, and suitable materials for use in quantum dot solar cells (QDSCs). Specifically, impact of halogen adatoms (Br, Cl, and F) on carboxyl edge-functionalized graphene quantum dot (CO2H-GQD) has been investigated employing DFT-based first-principles computations. We analyzed energy gaps (Eg), LUMO, and HOMO to determine how the foreign atom affects electronic features of material, employing hybrid functional B3LYP with a 6-31G basis set. In order to investigate charge separation and electron injection in both doped and undoped CO2H-GQD, we examined charge transfer (CT), molecular electrostatic potential (MESP), and binding mechanism. Optical attributes also indicate a wide spectrum in visible range, making it suitable for harvesting solar light. Furthermore, we evaluated solar cell parameters, including efficiency (η), short circuit current density (Jsc), fill factor (FF), and open circuit voltage (Voc) to assess potential usage of adatom-doped CO2H-GQD in quantum dot solar cell. Subsequent to Br, Cl, and F substitutional doping, value of η for CO2H-GQD increased. In case of F doping, we achieved maximum η, which has electron-donating nature and a larger radius, allowing it to inject more electrons into titanium dioxide (TiO2) surface. Based on our research, we have determined that these recently discovered sensitizers built upon GQD exhibit considerable potential for use in QDSCs.

Retracted: Interfacial Transport Study of Ultra-Thin InN-Enhanced Quantum Dot Solar Cells

Retracted: Interfacial Transport Study of Ultra-Thin InN-Enhanced Quantum Dot Solar Cells

PbS Colloidal Quantum Dots Infrared Solar Cells: Defect Information and Passivation Strategies

Large‐sized lead sulfide quantum dots (PbS QDs) offer strong absorption in the infrared, making them suitable for bottom cells in tandem devices. However, current QD‐based tandem devices underperform compared to single junction devices. This review focuses on defect information and passivation strategies in large‐sized QD solar cells. Defects from oxidation, polydispersity, and nonbonding sites on the (001) facet during QD synthesis are examined. Ligand‐exchange‐related defects such as tangled atoms, incomplete passivation, and excess ligands are analyzed. Surface and interface defects resulting from solar cell fabrication are also discussed. Strategies including cation exchange, thermodynamic growth, kinetic growth, and mixed halide ligands are summarized. Post‐treatment approaches could also help to address surface and interface defects. Large‐sized PbS‐QDs show promise as infrared radiation absorbers. Overcoming defects and implementing effective passivation strategies are crucial for single junction and tandem solar cells.

Absorption enhancement in GaAs based quantum dot solar cells using double-sided nanopyramid arrays.

Quantum dot solar cells (QDSCs) are regarded as one of the most efficient devices due to their intermediate band structures. A suitable light-trapping (LT) strategy matching the absorption spectrum is important to improve the photocurrent conversion efficiency of QDSCs. In this paper, we have proposed a design of the periodically patterned top and bottom dielectric nanopyramid arrays for highly efficient light trapping in GaAs-based QDSCs. The dielectric nanopyramid arrays significantly improve the light absorption of QDSCs in the longer wavelength between 0.8µm and 1.2µm. In addition, this LT structure ensures a completely flat window layer and back surface field layer while passivating these semiconductor surfaces. For the optimized double-sided structure, the short-circuit current generated by QDSC is 34.32m A/c m 2, where the photocurrent from the quantum dots (QDs) is 5.17m A/c m 2. Compared to the photocurrent of the QDSC without an LT structure, the photocurrent of the double-sided structure is increased by 84%. The QD photocurrent of the double-sided structure is increased by 570% compared to that of the QDSC without the LT structure.

Optimizing quantum dot solar cells: exploring defect density effects with PTAA HTL layer simulation using SCAPS-1D

In recent years, quantum dot solar cells have attracted attention due to their versatile electrical and optical properties as a material. A quantum dot solar cell can be tuned in terms of bandgap and size. In this work, the effect of defect density on the performance of a solar cell is studied with the help of the Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D) software. The defect densities of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA)/lead sulfide (PbS)–tetrabutylammonium iodide (TBAI) and lead sulfide–TBAI/titanium dioxide (TiO2) are varied from 1 × 1010 to 1 × 1017 cm−2, and the electron mobility of titanium dioxide, temperature and work function are also varied. These simulation-based quantum dot absorber-based solar cells may, in the future, prove to be extremely effective quantum dot solar cells.

Improved performance of quantum dot solar cells by type-II InAs/GaAsSb structure with moderate Sb composition

We demonstrate improved performance of quantum dot solar cells (QDSCs) by type-II InAs/GaAsSb structure. With a moderate Sb composition of 18% and high quality QDs, a high efficiency of 17.31% under AM1.5 G illumination is achieved, showing an improvement of 11.25% in efficiency relative to type-I InAs/InGaAs QDSC. This improvement can be attributed to a high fill factor (FF) of 72.37% compared to 63% of the latter because the type-II structure effectively suppresses carrier recombination losses in QDs. As Sb composition increases to 24%, the FF maintains at a high level of 72.67%, but the efficiency drops to 17% because the elevation of valence band (VB) in GaAsSb capping layer further enhances the hole confinement. And the confinement reduces external quantum efficiency (EQE) and short-circuit current density (Jsc). These results prove the potential of improving efficiency of QDSCs by type-II structure.

Recent progress in performance improvement strategies for quantum dot sensitization methods: Challenges, achievements, and future prospects

In the recent past, there has been an increase in the use of semiconductor nanostructures that convert solar energy to electrical energy. This has encouraged the development of better and more efficient solar cells (SCs). Numerous investigations have been conducted into synthesizing novel semiconductor materials and tuning the electronic properties based on the shape, size, composition, and assembly of the quantum dots to improve hybrid assemblies. Recent studies that are determining the prospects of quantum dot SCs can form the basis for improving photovoltaic efficiency. Here, we have reviewed studies that investigated the sensitization methods for fabricating highly efficient SCs. We also discussed some examples that would help other researchers who want to sensitize quantum dot (QD) SCs. Thereafter, we analyzed the main and popular strategies that can be used for sensitizing the QD SCs within the limitations, advantages, and prospects of fabricating high-efficiency and stable QDs. During this work, we offered strong technical support and a theoretical basis for improving the industrial applications of QD. In addition, we provide a reference that can inspire other researchers who aim to improve the performance of SCs.

Ultrathin Dimethylammonium Iodide Matrix: Suppressing Octahedral Distortion and Reconstructing Surface Ligands for Efficient CsPbI3 Quantum Dot Photovoltaics

Inorganic CsPbI3 quantum dots (QDs) have received increasing attention for their application in new‐generation solar cells. However, their poor phase stability due to the small ionic radius of Cs and their inhomogeneous energy landscape on the QD surface during ligand exchange remain as bottlenecks for the practical application of CsPbI3 QD photovoltaics. Herein, the unfavorable octahedral distortion is effectively suppressed by riveting dimethylammonium hydroiodide (DMAI) into the lattice structure. Moreover, DMAI reconstructs the surface ligands to create an ultrathin matrix that encloses the QDs. The ultrathin DMAI matrix effectively passivates the vacancy defects and allows efficient coupling and charge transport in the QD films. As a result, the CsPbI3 QD solar cell yields an efficiency approaching 15%. In addition, the increase in the Goldschmidt tolerance factor enhances the stability of the octahedral structure, resulting in significantly improved device stability.