Enhanced Power Conversion Efficiency Research Articles

Recent Progress in Cesium‐Based Lead‐Free Halide Double Perovskite Materials for Photovoltaic Applications

Perovskite materials have revolutionized photovoltaic technology and become the vanguard of current research owing to their facile solution processability and exceptional enhancement in power conversion efficiency (PCE), reaching 25.2% to date. Unfortunately, lead toxicity is the major hurdle for perovskite solar cells (PSCs) for their scalability and prevalent commercialization. To tackle the toxicity issue, lead‐free perovskite and double perovskite materials are potential contenders in the photovoltaic world. Herein, a comprehensive study of lead‐free halide double perovskite materials with the formula A2BB’X6 is provided. Notably, the structure and design of the lead‐free light‐harvesting layer of Cs2BB’X6 is emphasized. Moreover, different organic–inorganic lead‐free halide double perovskite layers‐based solar devices are explored with their designed configurations and physical parameters. Finally, recent significant advancement in lead‐free double PSCs are reviewed, and the future outlook associated with lead‐free double perovskite devices is also deliberated to attain a promising pathway toward highly efficient and stable perovskite solar devices.

Top Stack Optimization for Cu2BaSn(S, Se)4 Photovoltaic Cell Leads to Improved Device Power Conversion Efficiency beyond 6%

AbstractEarth‐abundant and air‐stable Cu2BaSnS4−xSex (CBTSSe) and related thin‐film absorbers are regarded as prospective options to meet the increasing demand for low‐cost solar cell deployment. Devices based on vacuum‐deposited CBTSSe absorbers have achieved record power conversion efficiency (PCE) of 5.2% based on a conventional device structure using CdS buffer and i‐ZnO/indium tin oxide (ITO) window layers, with open‐circuit voltage (VOC) posing the major bottleneck for improving solar cell performance. The current study demonstrates a >20% improvement in VOC (from 0.62 to 0.75 V) and corresponding enhancement in PCE (from 5.1% to 6.2% without antireflection coating; to 6.5% with MgF2 antireflection coating) for solution‐deposited CBTSSe solar cells. This performance improvement is realized by introducing an alternative successive ionic layer adsorption and reaction‐deposited Zn1−xCdxS buffer combined with sputtered Zn1−xMgxO/Al‐doped ZnO window/top contact layer, which offers lower electron affinities relative to the conventional CdS/i‐ZnO/ITO stack and better matching with the low electron affinity of CBTSSe. A combined experimental (temperature‐ and light intensity‐dependent VOC measurements) and device simulation (SCAPS‐1D) evaluation points to the importance of addressing relative band offsets for both the buffer and window layers relative to the absorber in mitigating interfacial recombination and optimizing CBTSSe solar cell performance.

Boosting photovoltaic performance for Sb2S3 solar cells by ionic liquid-assisted hydrothermal synthesis

Bulk and surface trap-states in the Sb2S3 films are considered one of the crucial energy loss mechanisms for achieving high photovoltaic performance in planar Sb2S3 solar cells. Because ionic liquid additives offer interesting physicochemical properties to control the synthesis of inorganic material, in this work we propose the addition of 1-Butyl-3-methylimidazolium hydrogen sulfate (BMIMHS) into a Sb2S3 hydrothermal precursor solution as a facile way to fabricate low-defect Sb2S3 solar cells. Lower presence of small particles on the surface, as well as higher crystallinity are demonstrated in the BMIMHS-assisted Sb2S3 films. Moreover, analyses of dark current density-voltage J–V curves, surface photovoltage transient and intensity-modulated photocurrent spectroscopy have suggested that adding BMIMHS results in high-quality Sb2S3 films and a successful defect passivation. Consequently, the best-performing BMIMHS-assisted device exhibits a 15.4% power conversion efficiency enhancement compared to that of control device. These findings show that ionic liquid BMIMHS can effectively be used to obtain high-quality Sb2S3 films with low-defects and improved optoelectronic properties.

High Performance and Stable Organic Solar Cells Fabricated by Y-Series Small Molecular Materials as the Interfacial Modified Layer

The organic solar cell (OSC) has received tremendous consideration for the impressive increased power conversion efficiency (PCE) from 11% to over 18% in the last decade, but another main parameter, the stability, still needs further study to meet the requirements of commercialization. Generally, the inverted structure device shows more stability than the conventional one owing to the structure characteristics, but even so, the performance and stability of the OSC device still need further improvement because of some undesirable contact between the electron transport layer (typically transition metal oxide like ZnO) and the active layer. Here, three Y-series small molecular acceptor materials (Y6, BTP-eC9, and L8-BO) are used as an interfacial modified layer (IML), which could optimize the interfacial characterization of the devices and thus enhance both the performance and stability. As a result, the insertion of the IML improved the interlayer charge transport capacity by passivating the surface of ZnO, leading to the enhancement of short circuit current density (JSC), fill factor, and PCE of the OSCs. Furthermore, because of the protection of the IML, the OSCs show outstanding stability compared to the control device (without IML), which could maintain 80% performance of the device over 150 h.

Surface passivation and hole extraction: Bifunctional interfacial engineering toward high-performance all-inorganic CsPbIBr2 perovskite solar cells with efficiency exceeding 12%

All-inorganic CsPbIBr2 perovskite solar cells (PSCs) have attracted considerable research attention in recent years due to their excellent thermal stability. However, their power conversion efficiencies (PCEs) are relatively low and still far below the theoretical limit. Here, we report the use of an organic dye molecule (namely VG1-C8) as a bifunctional interlayer between perovskite and the hole-transport layer in CsPbIBr2 PSCs. Combined experimental and theoretical calculation results disclose that the multiple Lewis base sites in VG1-C8 can effectively passivate the trap states on the perovskite films. Meanwhile, the π-conjugated dye molecule significantly accelerates the hole extraction from the perovskite absorber as evidenced by the photoluminescence analysis. Consequently, the VG1-C8 treatment simultaneously boosts the photovoltage and photocurrent density values from 1.26 V and 10.80 mA cm−2 to 1.31 V and 12.44 mA cm−2, respectively. This leads to a significant enhancement of PCE from 9.20% to 12.10% under one sun irradiation (AM 1.5G). To our knowledge, this is the record efficiency reported so far for CsPbIBr2 PSCs. Thus, the present work demonstrates an effective interfacial passivation strategy for the development of highly efficient PSCs.

Unraveling the Formation Mechanism of the 2D/3D Perovskite Heterostructure for Perovskite Solar Cells Using Multi-Method Characterization

The formation of a two-dimensional (2D) three-dimensional (3D) perovskite heterostructure has lately proved to be a promising way to improve the interface between the perovskite and electron/hole transport layers in perovskite solar cells, which is crucial for better device efficiency and stability. Herein, a spacer cation, 4-fluorophenethylammonium iodide, in isopropyl alcohol was used to form a thin 2D perovskite layer on top of a 3D triple-cation perovskite by a spin-coating deposition process. Therefore, a significant improvement in the device open-circuit voltage is obtained, leading to an enhanced power conversion efficiency. The formation mechanism of the 2D perovskite layer was studied by analyzing the structural, chemical, and optoelectronic properties of the layer, while varying several synthesis parameters. We reveal the presence of bromide inside the 2D phase and conclude with the existence of a concomitant formation mechanism, besides the most commonly described one involving the lead iodide (PbI2) excess contained in the 3D bulk. Therefore, we demonstrate how the stoichiometry of the 2D perovskite is affected by the chemical composition of the 3D layer underneath. This work provides new insights into the synthesis mechanisms of 2D/3D perovskite heterostructures, which could help to optimize their fabrication processes and develop new efficient and functional 2D/3D structures.

A synergistic effect of the ion beam sputtered NiO x hole transport layer and MXene doping on inverted perovskite solar cells

The synergistic effect of high-quality NiO x hole transport layers (HTLs) deposited by ion beam sputtering on ITO substrates and the Ti3C2T x MXene doping of CH3NH3PbI3 (MAPI) perovskite layers is investigated in order to improve the power conversion efficiency (PCE) of p-i-n perovskite solar cells (PSCs). The 18 nm thick NiO x layers are pinhole-free and exhibit large-scale homogeneous surface morphology as revealed by the atomic force microscopy (AFM). The grazing-incidence x-ray diffraction showed a 0.75% expansion of the face-centered cubic lattice, suggesting an excess of oxygen as is typical for non-stoichiometric NiO x . The HTLs were used to fabricate the PSCs with MXene-doped MAPI layers. A PSC with undoped MAPI layer served as a control. The size of MAPI polycrystalline grains increased from 430 ± 80 nm to 620 ± 190 nm on the doping, as revealed by AFM. The 0.15 wt% MXene doping showed a 14.3% enhancement in PCE as compared to the PSC with undoped MAPI. The energy-resolved electrochemical impedance spectroscopy revealed one order of magnitude higher density of defect states in the band gap of MXene-doped MAPI layer, which eliminated beneficial effect of reduced total area of larger MAPI grain boundaries, decreasing short-circuit current. The PCE improvement is attributed to a decrease of the work function from −5.26 eV to −5.32 eV on the MXene doping, which increased open-circuit voltage and fill factor.

High‐Crystalline Regioregular Polymer Semiconductor by Thermal Treatment for Thickness Tolerance Organic Photovoltaics

To successfully develop a regioregular polymer, poly[4,8‐bis(5‐(2‐hexyldecyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene][5,5′‐bis(7‐(4‐(2‐butyloctyl)thiophen‐2‐yl)‐6‐fluorobenzo[c][1,2,5]thiadiazol‐4‐yl)‐2,2′‐bithiophene] (PDBD‐FBT), a symmetric monomer synthesized in high yield by tin homo‐coupling reactions. PDBD‐FBT is suitable as a donor material in organic photovoltaics (OPVs) because it shows high crystallinity and strong face‐on packing properties. These properties were amplified by thermal annealing (TA). This causes a power conversion efficiency (PCE) enhancement in PDBD‐FBT‐based OPVs. Using PDBD‐FBT as a polymer donor and 2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐heptylundecyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2″,3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (Y6‐HU) as an electron acceptor, a PCE of 7.91% was achieved without any additive and TA at optimized active layer film thickness of approximately 100 nm. After TA, a PCE of 12.53% was achieved with a 58% increase compared with the reference devices. Owing to the strong crystallinities, trap‐assisted recombination occurs by excessively formed grain boundaries; however, efficient exciton dissociation sufficiently covers these drawbacks. Even in the approximately 340 nm‐thick film condition, this tendency is more pronounced (73% PCE enhancement is observed from 6.17% to 10.69% of PCE in the without and with TA devices, respectively). Our study demonstrates that it is possible to manufacture thickness‐insensitive OPVs based on regioregular polymers with strong crystallinity and face‐on characteristics, thereby providing a solution to the thickness variation of large‐area organic solar cell modules.

Small Molecule-Induced Modulation of Grain Crystallization and Ion Migration Leads to High-Performance MAPbI3 Mini-Modules

Perovskites have become a promising light-absorbing material for the fabrication of high-performance solar cells. But, the relatively low film quality of perovskites hinders the fabrication of large-area perovskite solar modules and long-period stability, which further slows down their industrial-scale commercialization. Here, we propose an N,N′-methylenebis(acrylamide) (MBAA) addition strategy for modulating grain crystallization and ion migration within methylammonium lead halide (MAPbI3), resulting in enhanced power conversion efficiency (PCE) and stability of MAPbI3-based solar modules. MBAA can help to form larger perovskite grains with less defects due to strong coordination interactions between the Pb atoms in MAPbI3 and the −NH and −CO functional groups in MBAA. We further found that MBAA was located at the surface of perovskite grains, which would block the ion migration (MA+/I–) and the H2O/O2 infusion from the ambient-air environment, resulting in enhancements of the PCE and stability of the MAPbI3 devices. The mini-module with an active area of 20 cm2 exhibits a record PCE of 18.58%. The MBAA-based solar module shows excellent damp heat and operational stabilities and maintains ∼82% and ∼90% of its initial PCE after 1000 h under 85 °C/85% relative humidity and 1000 h working at the maximum power point.

Theoretical designing of selenium heterocyclic non-fullerene acceptors with enhanced power conversion efficiency for organic solar cells: a DFT/TD-DFT-based prediction and understanding

In this study, we have designed and explored a new series of non-fullerene acceptors for possible applications in organic solar cells. We have designed four molecules named as APH1 to APH4 after end-capped modification of recently synthesized Y6-Se-4Cl molecule. Density functional theory and time dependent-density functional theory have been employed for computing geometric and photovoltaic parameters of the designed molecules. Designed molecules have displayed high values of fill factor and FF%. Further, high mobility of electrons and holes between metal electrodes are also noted for designed molecules. Good values of open circuit voltage enhance the power conversion efficiency in the APH1-APH4. Frontier molecular orbitals analysis and excitation energy values suggested easy transportation of charges between molecular orbitals. Moreover, red-shifting in the absorption spectrum with high oscillating strength is also noted in APH1 to APH4 as compared to reference molecules. Results of different opto-electronic and photovoltaic parameters recommended that APH1 to APH4 are effective contributors for the development of high performance organic solar cells.

Surface passivation boosted performances of perovskite solar cells assembled under ambient conditions

Boosted performances were measured for perovskite solar cells (PSCs) through interface engineering via surface passivation using p-toluenesulfonamide (PTSA) between the CH3NH3PbI3 (MAPbI3) and CuInS2 (CIS) hole transporting layer (HTL) films in ambient environment. All PSCs were assembled with an inexpensive architecture: FTO/block-TiO2 (b-TiO2)/mesoporous TiO2 (m-TiO2)/MAPbI3/CIS/carbon. Furthermore, to explore PTSA-x-y effects onto the PSCs performances, the PTSA concentration (x) and layer number (y) were varied. For this purpose, two PTSA concentrations of 50 and 100 mg/mL along with up to four layer numbers were spin-coated over the MAPbI3 film. The optimum PTSA concentration was found to be PTSA-50-2 indicating two layers of 50 mg/mL were coated on the perovskite layer. The SEM images exhibited that the PTSA-50-2 and PTSA-100-1 films had homogeneous surfaces without any pin-holes or tracks which were highly desirable to achieve high efficiency. The champion PSC contained the PTSA-50-2 interface layer which displayed the utmost power conversion efficiency (PCE) of 11.24% (JSC = 21.32 mA cm−2, VOC = 913.96 mV, FF = 0.58) demonstrating 64% PCE enhancement in comparison to that of champion reference cell assembled without PTSA film (PCE = 6.85%). Hence, surface passivation of the MAPbI3 perovskite by the PTSA was an appropriate approach to fabricate large scale and cost-effective PSCs.

Highly efficient A-site cation exchange in perovskite quantum dot for solar cells.

The mixed cation colloidal Cs1-XFAXPbI3 perovskite quantum dots (PQDs) obtained by cation exchange between CsPbI3 and FAPbI3 PQDs have been reported to exhibit enhanced photovoltaic performance. However, the cation exchange mechanism requires further in-depth investigation in terms of both material properties and device application. In this work, the impact of PQD weight ratio, PQD concentration, and host solvent polarity during cation exchange is comprehensively investigated for the first time. In addition, the whole exchange process under varying conditions is monitored by photoluminescence spectroscopy. As a result, we observe extremely fast cation exchange (∼20min) under a condition at a CsPbI3/FAPbI3 PQD weight ratio of 1:1, a concentration of 70 mg/ml, and a host solvent using toluene. Moreover, we directly fabricate a PQD solar cell device using these obtained mixed cation Cs0.5FA0.5PbI3 PQDs and achieved an enhanced power conversion efficiency of 14.58%. We believe that these results would provide more insights into the cation exchange in emerging PQDs toward efficient photovoltaic fabrication and application.

Extensive enhancement in power conversion efficiency of dye-sensitized solar cell by using Mo-doped TiO2 photoanode

Extensive enhancement in power conversion efficiency of dye-sensitized solar cell by using Mo-doped TiO2 photoanode

Dibenzo‐18‐Crown‐6‐Assisted Inhibition of Cation Migration for Stable Perovskite Solar Cells

Formamidinium–cesium (FACs)‐based perovskites are potential light‐absorbing materials for stable perovskite solar cells (PSCs), while long‐term stability deterioration caused by photo‐ and moisture‐induced cation migration and phase separation restrict their further commercial application. Herein, crown ether molecules with both, an electronegative cavity and a negatively charged π bond, dibenzo‐18‐crown‐6 (DB18C6), are introduced to FACsPbI3 films aiming at gaining better capability of inhibiting cation migration benefiting from the crown ether–cation complexation. Meanwhile, 18‐crown‐6 (18C6) with an electronegative cavity‐only is also employed for comparison. By tracing the changes of UV–vis absorption spectra, steady‐state photoluminescence, and Kelvin probe force microscopy of perovskite films under 24 h continuous light soaking, it is observed that the DB18C6‐modified FACsPbI3 film shows remarkably negligible degradation, in comparison with the unmodified and 18C6‐modified FACsPbI3 films. As a result, DB18C6‐modified PSCs with the architecture of ITO/SnO2/FACsPbI3/Spiro‐OMeTAD/Ag achieve an enhanced power conversion efficiency (PCE) exceeding 20.84%, which is a competitive efficiency for methylammonium‐free pure‐iodine n–i–p PSCs. The resultant unencapsulated DB18C6‐modified devices retain up to 94.73% and 90.18% of their original PCEs even after 500 h continuous full sunlight light soaking and 85 °C heating, respectively. Such crown ether modification provides a pathway on long‐term operational stabilized photovoltaics.

Enhancement of power conversion efficiency of dye-sensitized solar cell via symmetrical Bi-anchoring organic molecules as co-sensitizer

A strategy has carried to improvise the photovoltaic performance of DSSCs using auxiliary compounds as co-sensitizer along with organic sensitizer. Herein, bi-anchoring metal-free aromatic organic molecules (A-π-A) based co-sensitizer was utilized with organic sensitizer (DTTCY) and a Co 2+/3+ [bnbip] redox couple incorporated PEG-HEC quasi-solid-state electrolyte for an efficient DSSCs. Interestingly, ACY organic co-sensitized device (typically TiO 2 /ACY/DTTCY/Co 2+/3+ [bnbip]/PEG-HEC/Pt) has achieved a maximum power conversion efficiency of 8.3% under AM 1.5 G illumination (100 mW cm −2 ). At the same instance, NCY and PCY co-sensitized devices achieved comparably lower PCE of 7.44% and 6.99% respectively. These results prove that longer π-conjugation and bi-anchoring group of ACY molecules has induced electron injection process on TiO 2 surface. The influences of co-sensitizer are strongly covered the naked spectrum in the UV region and fill the vacant area in TiO 2 that induces a change in Quasi Fermi level of and decreases recombination flanked by photo-anode and oxidized cobalt species. The PCE results of ACY sensitized device are sustained by some electrochemical factors such as Bulk Resistance (R s = 17.23 Ω), Recombination Resistance (R Rec = 18.84 Ω), Charge Transfer Resistance (R CT = 1.136 Ω), Chemical capacitance (C μ = 13.66 μF), Ionic Conductivity (σ = 2.31 E −03 S cm −1 ), electron lifetime (τ n = 52.85 μs), electron transport time (τ d = 3.29.\μs) and collection efficiency (η COL = 93.97 %), rate of reaction constant (K eff = 18.92 s −1 ), Electron Density (n s = 1.21 E +17 cm −3 ), Dielectric constant (D eff = 0.011 mm 2 s -1 ), Dielectric Length (L n = 0.776 mm). The opportunity of trapping the co-sensitizer system functionalizes the anode surface supposed to avoid back electron transfer and dye degradation. The motive of the study is to enhance the photo-ability of metal-free DTTCY sensitizer along with metal-free co-sensitizer and metal-free additives integrated into the blend polymer electrolyte. • Design and synthesis of (A-π-A) based co-sensitizer for DSSCs application. • PEG-HEC polymer with Cobalt redox couple used as an effective QSS electrolyte. • ACY organic co-sensitized device has achieved a maximum PCE of 8.3%. • ACY co-sensitizer reduces recombination reaction in DSSCs.

Oxide/Halide/Oxide Architecture for High Performance Semi‐Transparent Perovskite Solar Cells

AbstractA device architecture with n‐type oxide/perovskite halide/p‐type oxide for the sputtering damage‐free semi‐transparent perovskite solar cells (PSCs) is reported. A p‐type nickel oxide (NiOx) nanoparticle overlayer on a perovskite layer is introduced to act as both a hole transporting layer and buffer layer to avoid sputtering damage during deposition of transparent conducting oxide. The NiOx based semi‐transparent PSCs exhibit superior durability under harsh sputtering conditions such as high temperature and sputtering power, enabling the high quality of transparent electrodes. With optimal sputtering condition for tin‐doped indium oxide (ITO) as a top transparent electrode, the semi‐transparent device shows an enhanced power conversion efficiency (PCE) of 19.5% (20.5% with a back reflector), which is higher than that of the opaque device (19.2%). The semi‐transparent devices also shows superior storage stability without encapsulation under 10% relative humidity, retaining over 90% of initial PCE for 1000 h. By controlling the molar concentration of perovskite solution, a semi‐transparent PSC with a PCE of 12.8%, showing a high average visible transmittance (AVT) of 30.3%, is fabricated. The authors believe that this architecture with n‐type oxide/perovskite halide/p‐type oxide represents a cornerstone for the high performance and commercialization of semi‐transparent PSCs.

Interface engineering utilizing bifunctional metformin for high performance inverted perovskite solar cells

Hydrophobic nature of hole transporting layers commonly employed in inverted perovskite solar cells (iPSCs), such as PTAA, hampers the fabrication of compact and high quality perovskite films above. Moreover, the defects at perovskite interface and grain boundaries directly deteriorate the power conversion efficiency (PCE) and stability of solar cells. Hence, the realization of high quality perovskites with reduced defects on hydrophobic substrate is critical but still challenging to further enhance the performance of iPSCs. It has been succeeded in this work through rational approach of interface engineering. Metformin, a preferred medicine for diabetes mellitus, is introduced as a bifunctional interfacial layer on PTAA surface. It is revealed that metformin can substantially improve the wettability of PTAA, and facilitate the fabrication of compact perovskite films. In addition, as a biguanidine molecule, it can effectively passivate the defects at the interface. Consequently, iPSCs with a dramatic PCE enhancement from 16.54% to 19.73% have been succeeded. Moreover, metformin can promote the device stability by maintaining the 90% of the initial PCE after a 600 h storage. • Metformin can substantially improve the wettability of PTAA, and facilitate the fabrication of compact perovskite films. • Metformin can effectively passivate the defects at the interface. • Metformin can enhance the PCE of iPSCs from 16.54% to 19.73%. • Metformin can promote the device stability by maintaining the 90% of the initial PCE after a 600 h storage.

A Multifunctional Fluorinated Polymer Enabling Efficient MAPbI3-Based Inverted Perovskite Solar Cells.

Exploring polymeric hole-transporting materials (HTMs) with passivation functions represents a simplified and effective approach to minimize the perovskite defect density. To date, most of reported polymeric HTMs were applied to fabricate n-i-p regular perovskite solar cells (PSCs). The polymers compatible for p-i-n inverted PSCs were very limited. Moreover, the passivation polymers were devoted to passivate the uncoordinated Pb2+. However, the MA+ cation defect has profound unwanted effect on device efficiency and long-term stability. In order to synchronously passivate the Pb2+ and MA+ defects in p-i-n inverted PSCs, a new nonfused polymer was intentionally explored via mild polymerization. The aromatic bridge instead of long alkyl chains enabled polymer BN-12 to achieve excellent thermal stability and good wettability of perovskite precursor. Furthermore, the incorporation of chemical anchor sites ("C═O" and "F") strongly controlled the crystallization of perovskite and restrained the MA+ ion migration. As a result, a significant fill factor (FF) of 82.9% and an enhanced power conversion efficiency (PCE) of 20.28% were achieved for MAPbI3-based devices with the dopant-free BN-12, exceeding those with the commercial HTM PTAA (FF = 81.7%, PCE = 19.51%). More importantly, the unencapsulated devices based on BN-12 realized outstanding long-term stability, maintaining approximately 95% of its initial efficiency after stored for 85 days. By contrast, the PTAA-based device showed rapid decrease which retained only 50% of its initial value after 45 days.

Light management in ultra-thin photonic power converters for 1310 nm laser illumination.

We designed and optimized ultra-thin single junction InAlGaAs photonic power converters (PPC) with integrated back reflectors (BR) for operation at the telecommunications wavelength of 1310 nm and numerically studied the light trapping capability of three BR types: planar, cubic nano-textured, and pyramidal nano-textured. The PPC and BR geometries were optimized to absorb a fixed percentage of the incident light at the target wavelength by coupling finite difference time-domain (FDTD) calculations with a particle swarm optimization. With 90% absorptance, opto-electrical simulations revealed that ultra-thin PPCs with 5.6- to 8.4-fold thinner absorber layers can have open circuit voltages (Voc) that are 9-12% larger and power conversion efficiencies (PCE) that are 9-10% (relative) larger than conventional thick PPCs. Compared to a thick PPC with 98% absorptance, these ultra-thin designs reduce the absorber layer thickness by 9.5-14.2 times while improving the Voc by 12-14% and resulting in a relative PCE enhancement of 3-4%. Of the studied BR designs, pyramidal BRs exhibit the highest performance for ultra-thin designs, reaching an efficiency of 43.2% with 90% absorptance, demonstrating the superior light trapping capability relative to planar and cubic nano-textured BRs.

Optimization of metal nanoparticles concentration in dye solution to enhance performance of dye sensitized solar cells

In this study, we incorporate metal nanoparticles of AuNP and AgNP into dye N-719 solution in order to enhance the light absorption of dye-sensitized solar cells (DSSCs) device. AuNP or AgNP was mixed into N-719 dye solution by optimized the concentration of metal NPs. The optical property of the mixtures was investigated by use of UV-Vis spectroscopy while the morphology of the solutions was captured by TEM microscopy. The performance of DSSCs was done by J-V measurement equipped with solar simulator under light illumination of 100mW/cm2. Our fabricated DSSC devices show the enhancement of current density and power conversion efficiency (PCE) with the incorporation of metal NPs into dye layer. Addition of gold nanoparticle capped by dodecanethiols (AuDT) 5.66 wt.% reveals the enhancement of PCE devices from 1.58% without AuDT as reference to 2.77% with AuDT. Similar case for the addition of AgSC8 into dye of DSSC gives the same tendencies.