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Investigating the Performance Improvement of a Photovoltaic System in a Tropical Climate using Water Cooling Method
摘要： The performance of a crystalline silicon photovoltaic (PV) system is greatly reduced with the increase of the temperature of the solar panels, especially in the tropics. In this study, a water-film cooling system was installed onto a retrofitted rooftop PV system, which is operating as a distributed generation system. The experiment shows that this method not only can reduce the thermal stress between the front and the back surfaces of the solar panels, it also minimises the non-uniform distribution of temperature across different positions of the solar panels. Besides, the cooling system with an optimal cooling water flow rate of 6 L/min can improve the power output by 32 W per 260-W-rated-PV-module (15% improvement) and with the net energy gain of 0.0178 kWh/hour/panel at 1150 W/m2 solar irradiance. In addition, the collected rainwater from the site is sufficient to cover the water needs for the cooling system. This method justifies that the proposed water-cooling method is technically feasible to provide a positive energy generation for a photovoltaic system.
关键词： temperature reduction,water cooling,distributed generation,photovoltaic performance,tropical climate
更新于2025-09-12 10:27:22
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Effect of Ligand Structures of Copper Redox Shuttles on Photovoltaic Performance of Dye-Sensitized Solar Cells
摘要： In recent years, copper(I/II) complexes have emerged as alternative redox shuttles in dye-sensitized solar cells (DSSCs), exhibiting more positive redox potential than iodine- and cobalt-based redox shuttles. In particular, copper(I/II) complexes with 1,10-phenanthroline- or 2,2′-bipyridyl-based ligands attained moderate to high power conversion efficiencies (6?11%) with a high open-circuit voltage (VOC) over 1.0 V due to the positive potentials. Although copper(I/II) complexes with 1,10-phenanthroline-based ligands with 2,9-substituents have been developed, the effect of their ligand structures on the photovoltaic performance of DSSCs have not been fully addressed due to limited synthetic access to 1,10-phenanthroline derivatives. In this study, we designed and synthesized a series of copper(I/II) complexes with 1,10-phenanthroline ligands with different substituents at the 2,9-positions: bis(2-n-butyl-1,10-phenanthroline)copper(I/II) ([Cu(bp)2]1+/2+), bis(2-ethyl-9-methyl-1,10-phenanthroline)copper(I/II) ([Cu(emp)2]1+/2+), bis(2,9-diethyl-1,10-phenanthroline)copper(I/II) ([Cu(dep)2]1+/2+), and bis(2,9-diphenyl-1,10-phenanthroline)copper(I/II) ([Cu(dpp)2]1+/2+). The more positive redox potentials of [Cu(emp)2]1+/2+ and [Cu(dep)2]1+/2+, compared to that of bis(2,9-dimethyl-1,10-phenanthroline)copper(I/II) ([Cu(dmp)2]1+/2+), originate from the larger steric hindrance of the ethyl group instead of the methyl group, whereas the redox potential of [Cu(bp)2]1+/2+ is significantly shifted to the negative direction because of the lower steric hindrance of the 2-monosubstituted 1,10-phenanthroline ligands. The efficiency of the DSSC with [Cu(bp)2]1+/2+ (5.90%) is almost comparable to the DSSC with [Cu(dmp)2]1+/2+ (6.29%). In contrast, the DSSCs with [Cu(emp)2]1+/2+ (3.25%), [Cu(dep)2]1+/2+ (2.56%), and [Cu(dpp)2]1+/2+ (2.21%) exhibited lower efficiencies than those with [Cu(dmp)2]1+/2+ and [Cu(bp)2]1+/2+. The difference can be rationalized by the electron collection efficiencies. Considering the similar photovoltaic properties of the DSSCs with [Cu(bp)2]1+/2+ and [Cu(dmp)2]1+/2+, the use of copper(I/II) complexes with 2-monosubstituted 1,10-phenanthroline ligands as the redox shuttle may be useful to improve the short-circuit current density while retaining the rather high VOC value when dyes with a smaller bandgap (i.e., better light harvesting) are developed.
关键词： copper(I/II) complexes,ligand structures,redox shuttles,photovoltaic performance,dye-sensitized solar cells
更新于2025-09-12 10:27:22
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Pressure-enhanced electronic coupling of highly passivated quantum dot films to improve photovoltaic performance
摘要： PbS colloidal quantum dot solar cells (CQDSCs) have recently achieved remarkable performance enhancement due to the development of the phase-transfer ligand exchange (PTLE) method. However, the lack of compact packing of the PTLE-passivated CQDs impairs the interdot electronic coupling and thereby severely restricts further improvement in performance. To address this electronic coupling issue, we report a simple yet effective process of external pressure (0–2 MPa). We ?nd that the interdot distance is reduced after the application of the pressure. Both optical and electrical measurements clearly demonstrate that the distance reduction can effectively strengthen the interdot electronic coupling, thus promoting the carrier transport of the CQD layer. However, too much pressure (>2 MPa) could accelerate the detrimental carrier recombination processes of CQDSCs. Accordingly, by optimizing the carrier transport and recombination processes, we achieve the maximum power conversion ef?ciency of 8.2% with a moderate pressure of 1.5 MPa, which is 25.5% higher than the solar cell without the external pressure. This effective strategy of external pressure could also be applied to other CQD-based optoelectronic devices to realize a better device performance.
关键词： external pressure,PbS colloidal quantum dot solar cells,phase-transfer ligand exchange,quantum dot films,Pressure-enhanced electronic coupling,photovoltaic performance
更新于2025-09-12 10:27:22
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PBDB-T and its derivatives: A family of polymer donors enables over 17% efficiency in organic photovoltaics
摘要： Due to the advantages such as being low cost, light weight, and flexible as well as having low toxicity, organic solar cells (OSCs) have attracted extensive interest. The field of OSCs progressed dramatically after the emergence of non-fullerene small molecule acceptors. In addition to the development of these acceptor materials, a key driver in the rapid progress of OSC research was the introduction of the PBDB-T polymer and its derivatives. In this review, we first give a brief overview of the structural features of PBDB-T congeners and the strategies used to design these polymers. The interesting aggregation effects of PBDB-T congeners in solution and solid-states are highlighted. Recent advances in the morphological understanding OSCs based on PBDB-T congeners are discussed using selected examples. In addition, the versatile applications of PBDB-T congeners in OSC devices, including interfacially modified binary, ternary and tandem devices, are also summarized. Importantly, we assess the energy loss and provide a meta-analysis of a library of high-performance PBDB-T type polymers, which are compared with other types of conjugated polymers. Finally, the remaining questions and the prospects of these exciting polymers are suggested.
关键词： organic solar cells,non-fullerene acceptors,photovoltaic performance,PBDB-T,polymer donors
更新于2025-09-12 10:27:22
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The effect of phase purification on photovoltaic performance of perovskite solar cells
摘要： Organic-inorganic hybrid perovskite solar cells (PSCs) have witnessed a rapid rising in power conversion ef?ciency (PCE) over the past few years; however, they still suffer from recombination loss via interface defects in perovskite ?lms. In this study, we implement an ef?cient phase puri?cation strategy by incorporating isopropyl alcohol (IPA) post-treatment of perovskite ?lms that reduces defect states and improves charge transport. It is found that the DMSO-PbI2-MAI complex in the perovskite ?lm is eliminated after IPA post-treatment. A suit of opto-electric characterizations demonstrates that the nonradiative recombination is greatly diminished, and charge extraction is effectively boosted in the modi?ed perovskite ?lms. The perovskite solar cells with phase-pure MAPbI3 achieve an impressively larger PCE of 18.78% than that of 17.1% for the control devices. Our work presents a facile and ef?cient path to performance improvement of PSCs.
关键词： phase purification,perovskite solar cells,photovoltaic performance,isopropyl alcohol
更新于2025-09-12 10:27:22
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Origin of the High Donor-Acceptor Composition Tolerance in Device Performance and Mechanical Robustness of All-Polymer Solar Cells
摘要： High tolerance regarding photovoltaic performance in terms of donor:acceptor (D:A) composition ratio is reported for all-polymer solar cells (all-PSCs), which is a crucial advantage in producing large-scale devices with high reproducibility. To understand the origin of high D:A ratio tolerance in all-PSCs, we investigate the molecular weight (MW) effects of the P(NDI2OD-T2) polymer acceptor (PA) on photovoltaic and mechanical robustness of PBDB-T:P(NDI2OD-T2) all-PSCs. Also, we compare the all-PSCs with other types of PSCs consisting of the same polymer donor but using small molecule acceptors (SMAs) including ITIC and PC71BM. It is observed that the D:A ratio tolerances of both the photovoltaic and mechanical properties are highly dependent on the PA MW and the acceptor material types. For example, at a high D:A ratio of 15:1, all-PSCs using high MW PA (number-average molecular weight (Mn)= 97 kg mol-1) exhibit 13 times higher normalized power conversion efficiency (PCE) than all-PSCs using low MW PA (Mn= 11 kg mol-1), and 20 times higher than ITIC-based PSCs. In addition, the electron mobilities in all-PSCs based on high MW PA are well maintained even at very high D:A ratio, whereas the electron mobilities in low MW PA all-PSCs and SMA-based PSCs decrease by 3- and 4-orders of magnitude, respectively, when the D:A ratio increases from 1:1 to 15:1. Thus, we suggest that the formation of tie molecules and chain entanglements by long polymer chains bridging adjacent crystalline domains is the main origin of excellent D:A tolerance in both mechanical robustness and photovoltaic performance. This work provides an important material design guideline for the reproducible production of flexible and stretchable all-PSCs.
关键词： molecular weight effects,mechanical robustness,donor-acceptor composition tolerance,photovoltaic performance,all-polymer solar cells
更新于2025-09-12 10:27:22
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Understanding the Impact of Side-chain on Photovoltaic Performance in Efficient All-polymer Solar Cells
摘要： In order to understand the impact of side-chain on photovoltaic performance and explore efficient All-polymer solar cells, chemical modifications on donor-acceptor based polymers containing benzo[1,2-b:4,5-b’]dithiophene (BDT) and thieno[3,4-c]pyrrole-4,6-dione (TPD) backbones were performed. Via side-chain fluorination, the molecular design resulted in lower highest occupied molecular orbital (HOMO) energy levels and enhanced backbone planarity. The intermolecular packing and solid-state ordering were found to significantly improve. These factors are considered as key influences for carrier transport. In contrast, introducing a bulky alkylthio substituent group was found to slightly distort the polymer backbone. As a result of the lower HOMO level, PTF8 exhibits an improved open circuit voltage (Voc) compared to the template polymer PT8. However, due to the increased crystallinity and aggregation, PTF8 and PTS8 experience an unfavorable phase separation in polymer-polymer bulk heterojunction blends, hindering the PCE to about 4%. Through introducing alkylthio side-chains and fluorination, the polymer PTFS8 exhibits an extremely low HOMO level (-5.73 eV). These reduced HOMO level limits charge separation between the donor and acceptor polymers. Without any fluorination and alkylthio side-chains, the wide bandgap polymer PT8 exhibits desired HOMO energy levels and crystallinity, delivering a best PCE of 8% together with a high Voc of 1.05 V, displaying its great potential for applications in efficient all-polymer optoelectronic devices.
关键词： BDT-TPD backbone,side-chain,fluorination,All-polymer solar cells,alkylthio substitution,photovoltaic performance
更新于2025-09-12 10:27:22
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Aqueous synthesis of Mn-doped CuInSe <sub/>2</sub> quantum dots to enhance the performance of quantum dot sensitized solar cells
摘要： Herein, we present the direct aqueous synthesis of manganese (Mn) doped CuInSe2 (Mn-CISe) quantum dots (QDs) under microwave irradiation to improve the photochemical properties of solar cells. As a result of Mn doping, the narrower bandgap energy of Mn-CISe leads to higher visible light absorption. The Mn-CISe QDs are therefore used as photosensitizers in quantum dot sensitized solar cells (QDSSCs), exhibiting enhanced performance which is dependent on Mn concentration. To the best of our knowledge, this is the ?rst time to construct an Mn-CISe sensitized-TiO2 photoanode to boost the photovoltaic performance of QDSSCs. The incorporation of Mn into CISe increases short-circuit current, which is ascribed to the e?ective injection of the excited electrons from QDs into TiO2 and the consequent higher electron lifetime, likely through a newly formed Mn midgap in the CISe band structure. Compared to the undoped QDs, Mn-CISe QDSSCs show a shorter electron transport time (τt) and a longer electron recombination time (τr) which are studied by intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy, respectively. In fact, a combination of higher light-harvesting e?ciency, slower charge recombination, and a longer electron lifetime gives rise to a maximum photovoltaic performance of 6.28%.
关键词： aqueous synthesis,Mn-doped CuInSe2,quantum dots,photovoltaic performance,quantum dot sensitized solar cells
更新于2025-09-12 10:27:22
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Bandgap Tunable Ternary Cd <sub/><i>x</i> </sub> Sb <sub/> 2– <i>y</i> </sub> S <sub/>3?δ</sub> Nanocrystals for Solar Cell Applications
摘要： We report the synthesis and photovoltaic performance of a new nonstoichiometric ternary metal sulfide alloyed semiconductor?CdxSb2?yS3?δ nanocrystals prepared by the two-stage sequential ionic layer adsorption reaction technique. The synthesized CdxSb2?yS3?δ nanocrystals retain the orthorhombic structure of the host Sb2S3 with Cd substituting a fraction (x = 0?0.15) of the cationic element Sb. The CdxSb2?yS3?δ lattice expands relative to the host, Sb2S3, with its lattice constant a increasing linearly with Cd content x. Optical and external quantum efficiency (EQE) spectra revealed that the bandgap Eg of CdxSb2?yS3?δ decreased from 1.99 to 1.69 eV (i.e., 625?737 nm) as x increased from 0 to 0.15. Liquid-junction CdxSb2?yS3?δ quantum dot-sensitized solar cells were fabricated using the polyiodide electrolyte. The best cell yielded a power conversion efficiency (PCE) of 3.72% with the photovoltaic parameters of Jsc = 15.97 mA/cm2, Voc = 0.50 V, and FF = 46.6% under 1 sun. The PCE further increased to 4.86%, a respectable value for a new solar material, under a reduced light intensity of 10% sun. The PCE (4.86%) and Jsc (15.97 mA/cm2) are significantly larger than that (PCE = 1.8%, Jsc = 8.55 mA/cm2) of the Sb2S3 host. Electrochemical impedance spectroscopy showed that the ZnSe passivation coating increased the electron lifetime by three times. The EQE spectrum of CdxSb2?yS3?δ has a maximal EQE of 82% at λ = 350 nm and covers the spectral range of 300?750 nm, which is significantly broader than that (300?625 nm) of the Sb2S3 host. The EQE-integrated current density yields a Jph of 11.76 mA/cm2. The tunable bandgap and a respectable PCE near 5% suggest that CdxSb2?yS3?δ could be a potential candidate for a solar material.
关键词： ternary metal sulfide,CdxSb2?yS3?δ nanocrystals,photovoltaic performance,quantum dot-sensitized solar cells,bandgap tunable
更新于2025-09-12 10:27:22
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The role of cation and anion dopant incorporated into a ZnO electron transporting layer for polymer bulk heterojunction solar cells
摘要： Doping is a widely-implemented strategy for enhancing the inherent electronic properties of charge transport layers in photovoltaic devices. A facile solution-processed zinc oxide (ZnO) and various cation and anion-doped ZnO layers were synthesized via the sol–gel method and employed as electron transport layers (ETLs) for inverted polymer solar cells (PSCs). The results indicated that all PSCs with doped ZnO ETLs exhibited better photovoltaic performance compared with the PSCs with a pristine ZnO ETL. By exploring the role of various anion and cation dopants (three compounds with the same Al3+ cation: Al(acac)3, Al(NO3)3, AlCl3 and three compounds with the same Cl? anion: NH4Cl, MgCl2, AlCl3), we found that the work function changed to favor electronic extraction only when the Cl anion was involved. In addition, the conductivity of ZnO was enhanced more with the Al3+ cation. Therefore, in inverted solar cells, doping with Al3+ and Cl? delivered the best power conversion efficiency (PCE). The maximum PCE of 10.38% was achieved from the device with ZnO doped with Al+ and Cl?.
关键词： electron transport layers,Al3+ cation,polymer solar cells,doping,Cl? anion,photovoltaic performance,power conversion efficiency,sol–gel method,zinc oxide
更新于2025-09-12 10:27:22