Higher Jsc Research Articles

Machine learning approach for predicting high JSC donor molecules in fullerene-typed organic solar cells

This study aimed to identify donor molecules that enhance the JSC in fullerene-type organic thin-film solar cells using materials informatics. After performing principal component analysis and Random Forest for feature selection, LASSO and Ridge regressions and SVR were developed. A genetic algorithm generated 250 new donor molecules, and SVR predicted that (i) 4H-cyclopentadithiophene, (ii) fluorine-containing structures, and (iii) C = O groups adjacent to thiophenes improve the JSC.

Optimizing strategy of bifacial TOPCon solar cells with front-side local passivation contact realized by numerical simulation

The tunnelling oxide passivation contact (TOPCon) solar cells have been impressive in the global photovoltaic (PV) market originating from their high efficiency and stability. However, it exhibits significant recombination losses due to its boron diffusion, laser damage and metal-semiconductor contact on front side. The bifacial TOPCon structure demonstrates massive potential in the improvement of passivation and contact performance with the premise that it can solve the parasitic absorption of polycrystalline silicon (poly-Si). In this study, the localized poly finger structure with excellent optics and passivation performance is designed in the front side of bifacial solar cells to compare with traditional TOPCon and full-area poly passivation devices. The theoretical efficiency and detailed power loss analysis in our simulation reveal that suppressing the recombination of FSF (front surface field) and the contact area is the crucial strategy to improve device performance, with optimized efficiency of 26.62 % and FF of 85.16 %. These results indicate that the route of BJ (back junction) structure containing localized selective contact and full coverage high-quality passivation holds potential in realizing both high Jsc and Voc for FBC (front and back contact) solar cells, featuring great instructive significance for future industrialization of PV production.

Metal-free phenothiazine dyes with alkoxy chains modified at different position for dye-sensitized solar cells

Long alkyloxy or alkoxyphenyl chains are commonly introduced to organic dye sensitizers in dye-sensitized solar cells (DSSCs) to inhibit the aggregation of sensitizer on the TiO2, thereby minimizing charge recombination. Here, we synthesized four D-D-π-A sensitizers (TP-C6, TP-PhOC6, C6O-TP-C6, C6O-TP-PhOC6), that feature alkyl-/alkoxyphenyl- moiety in phenothiazine (PTZ) donor’s N-position, and either alkoxy or no alkoxy groups in triphenylamine (TPA) auxiliary donor. Then, their photophysical, electrochemical and DSSCs properties were investigated. The UV-Vis and electrochemical studies revealed that all four dyes exhibited good light absorption ability and appropriate HOMO-LUMO energy levels. The introduction of alkoxy at the donor or auxiliary donor can result in a significant redshift in absorption. Among them, TP-PhOC6, which incorporates an alkoxy phenyl group at the N-position of PTZ and lacks alkoxy in TPA, induces a greater redshift in ICT absorption with strong absorption intensity. Additionally, in TP-PhOC6 based DSSC, mitigated charge recombination was observed. As a result, this device exhibited the strongest and widest IPCE spectrum, the highest Jsc (12.77 mA/cm²) and Voc (0.85 V), leading to the highest PCE (6.59 %).

Ternary polymer solar cells using two nonfullerene acceptors with cascading energy level and complementary absorptions

In this paper, we have fabricated ternary PSC with BTP-eC9 as the host acceptor, IT-M as the guest acceptor, and PM6 as donor. The optimized ternary PSC (PM6:BTP-eC9:IT-M ratio is 1:1.2:0.2) has the highest power conversion efficiency (PCE) of 17.06 % compared to the PM6:BTP-eC9 binary PSC (16.46 %) and PM6:L8-BO reference binary PSC (16.92 %). We systematically investigated the effect of blend acceptors on morphology, photovoltaic performance and charge carrier dynamics. After the addition of IT-M to PM6:BTP-eC9 binary film, the highest JSC (from 26.39 to 26.82 mA cm−2) was achieved for optimized ternary PSCs compared to PM6:BTP-eC9 binary PSC, which was attributed to the high efficiency of light absorption in the medium to long-wavelength region of IT-M. Shallower lowest unoccupied molecular orbitals (LUMO) level of IT-M enlarged the optical bandgap, which leads to an increase in the open-circuit voltage (VOC, from 0.86 V to 0.875 V). In addition, a small amount of IT-M improves the surface and bulk morphology and crystallinity of the ternary film. The ternary films shown high charge mobility ability. This work demonstrates that supplementing the light absorption and broadening the optical bandgap of PM6:BTP-eC9 binary films by IT-M as third component can effectively improve the PCE and obtain higher photovoltaic performance than that of PM6:BTP-eC9 binary PSCs and PM6:L8-BO reference binary PSCs.

Towards efficiency enhancement of earth abundant Cu2BaSn(S,Se)4 chalcogenide solar cell using In2S3 as efficient electron transport layer

Cu2BaSn(S,Se)4 (CBTSSe) solar cells, are an intriguing kind of photovoltaic devices with theoretical efficiency close to 31 %. Their promise in the field of renewable energy is highlighted by their sustainable structure, as well as their low density of defects. Even with these benefits, the record efficiency for CBTSSe solar cells is now only 5.2 %. In order to identify limitations in performance and clear the path for obtaining improved practical efficiency, this emphasizes the vital requirement for deep analysis. In this work, we investigate a new structure based on Cd free In2S3/CBTSSe heterojunction in which an Indium (III) sulfide as ETL layer, and CBTSSe as absorber layer take the place of the traditional CdS/ CBTSSe structure. For the first time, an analytical model that incorporates a variety of recombination mechanisms occurred in CBTSSe solar cell, such as Auger, Shockley-Read-Hall (SRH), interface recombination, tunneling-enhanced recombination, and non-radiative recombinations is proposed. In our approach the reverse saturation mechanism is taken into account in the suggested model as a metric to identify the main recombination mechanism. Significantly, there is a good agreement between the outcomes of our model and the experiment. It is shown that CBTSSe bulk recombination, In2S3/CBTSSe interface recombination and resistances are dominating. Besides, the developed model serves as fitness function for MOGA approach to locate the optimal parameters design combination that led to optimal efficiency. We demonstrate the ability to obtain an efficiency of up to 10.12 % by carefully tuning both the CBTSSe bulk material parameters and the In2S3/CBTSSe interface features. Our findings demonstrate that the optimized design using In2S3/CBTSSe heterojunction outperforms the baseline, reaching a high JSC of 20.57 mA/cm2, VOC of 0.88 V, and FF of 55.54 %, with appropriate band alignment at the In2S3/CBTSSe interface and optimized physical and geometrical parameters. The suggested approach paves the way for additional design optimization while also making it possible to identify the degradation factors that are responsible.

Efficient Micrometer Thick Bifacial Perovskite Solar Cells

AbstractPerovskite solar cells have become promising candidates for thin‐film photovoltaics (PV), but many record cells suffer from losses in current (≈3–4 mA cm−2). This is due to the choice of superstrate configurations (i.e., glass‐side illumination) and thin absorber layers, typically on the order of ≈500 nm. Illumination through a top transparent conductive oxide electrode (substrate configuration) using LiF and Al2Ox as anti‐reflective coatings leads to reflectance losses below 1% is demonstrated. When combined with 1 µm thick absorber layers, substrate configurated bifacial devices have power conversion efficiencies >20%, with minimized reflection losses approaching 98% of their detailed‐balance limits and higher Jsc than their monofacial counterparts. Further analysis is conducted to show there is still a significant fraction of current lost due to poor charge‐carrier extraction (e.g., resistive or low mobility contacts). This is studied by a direct comparison of photoluminescence at short‐circuit versus open‐circuit estimating a 4.5% loss in charge‐carrier collection.

Cu-Doped Sb2Se3 Thin-Film Solar Cells Based on Hybrid Pulsed Electron Deposition/Radio Frequency Magnetron Sputtering Growth Techniques

In recent years, research attention has increasingly focused on thin-film photovoltaics utilizing Sb2Se3 as an ideal absorber layer. This compound is favored due to its abundance, non-toxic nature, long-term stability, and the potential to employ various cost-effective and scalable vapor deposition (PVD) routes. On the other hand, improving passivation, surface treatment and p-type carrier concentration is essential for developing high-performance and commercially viable Sb2Se3 solar cells. In this study, Cu-doped Sb2Se3 solar devices were fabricated using two distinct PVD techniques, pulsed electron deposition (PED) and radio frequency magnetron sputtering (RFMS). Furthermore, 5%Cu:Sb2Se3 films grown via PED exhibited high open-circuit voltages (VOC) of around 400 mV but very low short-circuit current densities (JSC). Conversely, RFMS-grown Sb2Se3 films resulted in low VOC values of around 300 mV and higher JSC. To enhance the photocurrent, we employed strategies involving a thin NaF layer to introduce controlled local doping at the back interface and a bilayer p-doped region grown sequentially using PED and RFMS. The optimized Sb2Se3 bilayer solar cell achieved a maximum efficiency of 5.25%.

High-efficiency D-D-type wide bandgap polymer donor based on dibenzopyran unit

Pyran units as a six-membered heterocyclic nonaromatic containing one sp3 hybridized carbon and an oxygen have been widely employed to exploit donor and acceptor materials, and excellent power conversion efficiencies (PCEs) can be achieved for polymer solar cells (PSCs). In this work, a dibenzopyran (DBP) building block and a benzodithiophene (BDT) derivative as donor unit were utilized to successfully prepare a novel donor–donor (D-D)-type wide bandgap polymer PBDBP. The polymer PBDBP possesses an ultra-wide optical bandgap of 2.18 eV due to the weak intramolecular charge-transfer effect. Meanwhile, a low-lying HOMO energy of −5.41 eV is achieved, which is beneficial to realize a high Voc. Additionally, PBDBP also exhibits a complementary absorption with a narrow bandgap Y6 ranging from 300 to 950 nm, which can facilitate to improve light-harvesting ability for high Jsc. Finally, PBDBP:Y6 based device exhibits a high PCE of 11.43 % (Voc = 0.89 V, Jsc = 23.14 mA/cm2, and FF = 55.66 %). Our research indicates that the D-D-type polymer PBDBP based on dibenzopyran unit is a promising wide bandgap donor material for PSCs.

Cyanoesterthiophene Based Low‐Cost Polymer Donors for High Efficiency Organic Solar Cells

AbstractTo achieve commercial application of organic solar cells (OSCs), it is necessary to reduce material costs and improve device efficiency. This paper reports on the utilization of a multifunctional building block, namely 3‐cyanoesterthiophene, which exhibits simple structure and accessibility of synthetic for cost‐effective and high‐performance polymer donors (PDs). Meanwhile, ternary and terpolymerization strategies have been studied. Two similar PDs, PBTCl0‐TCA and PBTCl100‐TCA, are synthesized, and the devices exhibit less‐than‐satisfactory efficiency of 13.21% and 11.53% due to mismatching energy level and imperfect morphology. The two PDs with comparable structures and commendable compatibility easily form alloy‐like phase in active layer, which can effectively boost the efficiency of ternary devices to 14.17% with retained high JSC and significant improved open‐circuit voltage (VOC) and fill factor (FF). Encouraged by the ternary blending phenomenon, a polymer donor (PBTCl50‐TCA) with same ratio by random terpolymerization is designed. And over 17% efficiency binary OSCs using terpolymerization donor are demonstrated. The synergies of incorporation of the cyanoester‐group and terpolymer endow the developed PDs with deep‐lying energy levels, face‐on orientation, thermodynamic miscibility with the prevailing nonfullerene acceptor and appropriate polymer crystallinity. The findings study provide valuable insights and support for the advancement of cost‐effective and high‐performance PDs.

Optical loss analysis of Sb2S3 and Sb2Se3 thin film solar cells: A Quantitative Assessment

Optical loss either by light reflection, or light absorption in different layers of a solar cell, can significantly impact short-circuit current density. In this paper, an optical model has been developed to analyze the optical loss in thin film solar cells made of CdS/Sb2S3 or CdS/Sb2Se3 antimony chalcogenide. This model is based on optical loss from absorption in thin layers and reflection at the interfaces of glass/TCO/CdS/(Sb2S3 or Sb2Se3) only by considering the optical properties of layers (refractive index and extinction coefficient). The transmission and reflection rate of Sb2S3 or Sb2Se3 show almost a similar trend. The absorptivity and relative loss in short-circuit current density (Jsc) versus the thickness of Sb2S3 and Sb2Se3 layers was calculated for two different structures: glass/TCO/CdS/Sb2S3 and glass/TCO/CdS/Sb2Se3. The Sb2Se3 solar cell shows a slightly better conversion performance compared to Sb2S3 solar cell due to lower reflection loss. The light reflection was calculated at four interfaces. The transmission rate of light through TCO, ITO, and CdS layers was calculated to obtain an optimal thickness for these layers. TCO showed a higher transmission rate and thus is preferred in antimony solar cell structures. The variations of (Jsc) and loss for Jsc with different thicknesses of ITO (>20%) or TCO (<20%) contact layers, favoring TCO for its lower optical losses and higher Jsc (24 mA cm−2).

Active Contour Models for Boundary Extraction with Application to Medical Images with Noise

In medical image processing, active contour model is a method used to segment or extract the boundaries of an image for further processing. Recently, a selective active contour model called Selective Segmentation with Chessboard Distance (SSCD) model has been proposed to effectively segment a particular object in an image. However, the SSCD model has problems in extracting noisy images, which may result in poor segmentation. It is known that the presence of noise in some medical images cannot be avoided and can lead to poor segmentation. The aim of this research is therefore to reformulate the SSCD model to segment some medical images with noise. The modification is done by considering two different image denoising algorithms, the Gaussian filter and the bilateral filter, as new fitting terms in the SSCD model, resulting in two variants of modified SSCD models, referred to as SSCDG and SSCDB, respectively. The accuracy of the segmented image was evaluated using the Jaccard (JSC) and Dice similarity coefficient (DSC). Numerical experiments showed that the proposed SSCDG model based on the Gaussian filter denoising algorithm has the highest JSC and DSC values, which means the highest segmentation accuracy compared to the SSCD and SSCDB models. In the future, the proposed model can be extended to three-dimensional and color formulations.

Numerical investigation on the role of ZnTe back surface layer in an efficient CuInS2 thin film solar cell

This paper presents the modeling and numerical inspection of an efficient CuInS2-based n-CdS/p-CuInS2/p+-ZnTe thin film solar cell applying the SCAPS-1D simulator. The various parameters used in the simulation have been obtained from existing literature. The optimization of the device has considered the width, doping concentration, and defect density of individual layer. The optimized standalone CuInS2 device shows an efficiency of 16.83%. Addition of ZnTe in the device gives an impressive efficiency of approximately 28.67%, having a current density, JSC of 25.58 mA cm−2, a VOC of 1.25 V, and an FF of 89.12%. The superior VOC is a result of the increased built-in potential formed at the hetero-interfaces of the device and the decrease in surface recombination velocity by back surface field effect in the ZnTe layer. The highest JSC is ascribed to the enhancement of the absorption of vis-infrared photons by back surface field (BSF) effect in the ZnTe layer. These findings demonstrate the potential for manufacturing high efficiency CuInS2-based thin film solar cells in the future.

NIR-absorbing polymer acceptor for efficient all-polymer solar cells with a record-high photocurrent of 26.5 ​mA ​cm−2

Achieving high short-circuit current density (JSC) to boost power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs) is a major challenge, mainly due to the difficulty in developing high-performance near-infrared (NIR)-absorbing polymer acceptors. Herein, a new polymer acceptor named PY2Se–4F employing a Y-series small-molecule acceptor as the precursor is designed and synthesized. Thanks to its unique molecular backbone structure combining selenophene-fused central core and bi-fluorinated end-group, PY2Se–4F shows desirable NIR-absorption with a spectral onset approaching 1000 ​nm, which is beneficial for obtaining high JSC when matched with wide bandgap polymer donors such as PM6 and D18. For the binary all-PSCs, PM6:PY2Se–4F delivers a record-high JSC of 26.5 ​mA ​cm−2, which is superior to that of D18:PY2Se–4F, mainly due to stronger absorption in the range of 600–700 ​nm. In contrast, the D18:PY2Se–4F combination exhibits more favorable blend morphology, higher and more balanced charge-transporting, and less non-radiative energy loss compared with the PM6:PY2Se–4F. As a result, the D18:PY2Se–4F-based devices offer an improved PCE of 16.1 ​% with a JSC of 25.5 ​mA ​cm−2 and both higher photovoltage and fill factor, while the related PCE and JSC are ones of the top values among the reported binary all-PSCs. The results indicate that PY2Se–4F is a promising NIR-absorbing polymer acceptor for obtaining efficient all-PSCs with record-high JSC.

Unidirectional Sidechain Engineering to Construct Dual-Asymmetric Acceptors for 19.23 % Efficiency Organic Solar Cells with Low Energy Loss and Efficient Charge Transfer.

Achieving both high open-circuit voltage (Voc ) and short-circuit current density (Jsc ) to boost power-conversion efficiency (PCE) is a major challenge for organic solar cells (OSCs), wherein high energy loss (Eloss ) and inefficient charge transfer usually take place. Here, three new Y-series acceptors of mono-asymmetric asy-YC11 and dual-asymmetric bi-asy-YC9 and bi-asy-YC12 are developed. They share the same asymmetric D1 AD2 (D1 =thieno[3,2-b]thiophene and D2 =selenopheno[3,2-b]thiophene) fused-core but have different unidirectional sidechain on D1 side, allowing fine-tuned molecular properties, such as intermolecular interaction, packing pattern, and crystallinity. Among the binary blends, the PM6 : bi-asy-YC12 one has better morphology with appropriate phase separation and higher order packing than the PM6 : asy-YC9 and PM6 : bi-asy-YC11 ones. Therefore, the PM6 : bi-asy-YC12-based OSCs offer a higher PCE of 17.16 % with both high Voc and Jsc , due to the reduced Eloss and efficient charge transfer properties. Inspired by the high Voc and strong NIR-absorption, bi-asy-YC12 is introduced into efficient binary PM6 : L8-BO to construct ternary OSCs. Thanks to the broadened absorption, optimized morphology, and furtherly minimized Eloss , the PM6 : L8-BO : bi-asy-YC12-based OSCs achieve a champion PCE of 19.23 %, which is one of the highest efficiencies among these annealing-free devices. Our developed unidirectional sidechain engineering for constructing bi-asymmetric Y-series acceptors provides an approach to boost PCE of OSCs.

Unidirectional Sidechain Engineering to Construct Dual‐Asymmetric Acceptors for 19.23 % Efficiency Organic Solar Cells with Low Energy Loss and Efficient Charge Transfer

AbstractAchieving both high open‐circuit voltage (Voc) and short‐circuit current density (Jsc) to boost power‐conversion efficiency (PCE) is a major challenge for organic solar cells (OSCs), wherein high energy loss (Eloss) and inefficient charge transfer usually take place. Here, three new Y‐series acceptors of mono‐asymmetric asy‐YC11 and dual‐asymmetric bi‐asy‐YC9 and bi‐asy‐YC12 are developed. They share the same asymmetric D1AD2 (D1=thieno[3,2‐b]thiophene and D2=selenopheno[3,2‐b]thiophene) fused‐core but have different unidirectional sidechain on D1 side, allowing fine‐tuned molecular properties, such as intermolecular interaction, packing pattern, and crystallinity. Among the binary blends, the PM6 : bi‐asy‐YC12 one has better morphology with appropriate phase separation and higher order packing than the PM6 : asy‐YC9 and PM6 : bi‐asy‐YC11 ones. Therefore, the PM6 : bi‐asy‐YC12‐based OSCs offer a higher PCE of 17.16 % with both high Voc and Jsc, due to the reduced Eloss and efficient charge transfer properties. Inspired by the high Voc and strong NIR‐absorption, bi‐asy‐YC12 is introduced into efficient binary PM6 : L8‐BO to construct ternary OSCs. Thanks to the broadened absorption, optimized morphology, and furtherly minimized Eloss, the PM6 : L8‐BO : bi‐asy‐YC12‐based OSCs achieve a champion PCE of 19.23 %, which is one of the highest efficiencies among these annealing‐free devices. Our developed unidirectional sidechain engineering for constructing bi‐asymmetric Y‐series acceptors provides an approach to boost PCE of OSCs.

Influence of spacer and donor groups as tetraphenylethylene or triphenylamine in asymmetric zinc phthalocyanine dyes for dye-sensitized solar cells

Based on the available literature, the carboxylic acid is a suitable electron-withdrawing group for the development of push–pull type AB3 phthalocyanines that can be used in dye-sensitized solar cell (DSSC). This study aims to assess the impact of carboxylic acid groups on solar cell energy conversion efficiency. Two types of carboxylic acid groups were selected as electron-withdrawing groups for this purpose. These groups were attached to the phthalocyanine (Pc) core either directly or via conjugated linker groups. Two novel push–pull zinc phthalocyanine dyes (GT-52 and GGC-22) containing tetraphenylethylene (TPE) or triphenylamine (TPA) substituents as electron donor groups and carboxylic acid or phenoxy carboxylic acid as anchoring groups, respectively, have been synthesized to construct DSSCs. The optical, electrochemical, and photovoltaic properties of the effect of the spacer and electron donor groups in these phthalocyanines are evaluated. Both dyes exhibit good anti-aggregation ability owing to the presence of the bulky donor groups. On the other hand, the DSSC based on GGC-22 showed a significantly higher power conversion efficiency (PCE) of 2.15% than that of GT-52 (0.26%) under AM 1.5G solar conditions. The superior performance of GGC-22 is attributed to the introduction of a phenoxy spacer, which results in a longer distance between the donor groups and the TiO2 surface compared to GT-52 without any spacer. This allows for higher dye loading, resulting in higher JSC, VOC, and PCE for GGC-22. As a result, the presence of a longer anchoring group for the donor groups is an important synthetic strategy for efficient phthalocyanine-based DSSCs.

Field-Effect Passivation of the Cu2O/ZnO Transparent Heterojunction Photovoltaic Device Using Ga2O3 Thin Film

Photovoltaics (PV) would be more promising if light could generate electric power invisibly. This will endow more degrees of freedom to PV cells for wide-range deployment. Transparent photovoltaic (TPV) devices are the groundwork of the building-integrated photovoltaic (BIPV) systems that provide aesthetics to the buildings and solar energy convertor modules. TPV is adequate for the BIPV system of windows. Heterojunctions between p-type Cu2O and n-type ZnO have emerged as one of the most promising TPV devices. However, their inadequate transparency and a deficit of open-circuit voltage (VOC) and short-circuit current density (JSC) remained an open challenge. In this work, we have fabricated a thin Ga2O3 buffer layer embedded transparent ZnO/Cu2O heterojunction photovoltaic device, showing an average visible transmittance of more than 50%. The insertion of the Ga2O3 buffer layer remarkably increases the JSC and VOC to ∼860% and ∼41%, respectively. The TPV device also demonstrated a high JSC of 3.41 mA/cm2 under UV light. The Ga2O3 layer provides a graded conduction band alignment and passivates the interface by the field-effect passivation mechanism. The Ga2O3 buffer layer embedded device also demonstrated a broadband photodetection with remarkably high responsivity and detectivity of 250 mA/W and 5 × 1011 Jones at self-biased conditions.

Heterojunction solar cell based on donor-acceptor pi-conjugated naphthalene bisbenzimidazole, perylene bisbenzimidazole, and naphthalene imidazole: A spectroscopic, microscopic and DFT assessment.

This study represents detailed vibrational analysis of naphthalene bisbenzimidazole (NBBI), perylene bisbenzimidazole (PBBI), and naphthalene imidazole (NI) by vibrational spectroscopic (Fourier Transform Infrared (FT-IR) and Raman), Atomic Force Microscopic (AFM) and quantum chemical studies for the first time. These sorts of compounds provide an opportunity to build potential n-type organic thin film phototransistors which can be used as organic semiconductors. Optimized molecular structures and vibrational wavenumbers of these molecules in their ground states have been calculated by Density Functional Theory (DFT) using B3LYP functional with 6-311++G(d,p) basis set. Finally, theoretical UV-Visible spectrum was predicted and Light Harvesting Efficiencies (LHE) were evaluated. AFM analysis revealed that PBBI has the highest surface roughness thus exhibits an increase in high Jsc value and high conversion efficiency.

Dye‐Sensitized Solar Cells with Efficiency over 36% under Ambient Light Achieved by Cosensitized Tandem Structure

The cosensitization process is an effective way to improve the performance of dye‐sensitized solar cells (DSSCs), especially for tandem cells that employ the complementary light harvest ranges of different dyes. Herein, various cosensitized DSSCs are prepared using D35, XY1b, and Y123 dyes and employed to construct cobalt tandem DSSCs. First, the performance of single cells with and without scattering layers is studied. The results show that the cosensitized cells using D35 + XY1b and XY1b + Y123 dyes have higher power conversion efficiency (PCE) than the others, attributed to their longer light absorption wavelength and higher charge recombination resistance. Furthermore, the XY1b + Y123 cell has significantly higher open circuit voltage (Voc) but slightly lower current density (Jsc) than those of the D35 + XY1b cell. The cosensitized systems are further utilized to prepare tandem cells. Photoelectrodes without and with scattering layers are used as top and bottom cells, respectively. It shows that by using D35 + XY1b (higher Jsc) and XY1b + Y123 (higher Voc) as sensitizers of top and bottom cells, respectively, a PCE as high as 36.27% can be achieved under fluorescent lighting. The cells using these dyes have high long‐term stability at room temperature.

Novel Metal Complexes Unit of Phenanthroline Derivative for Being Used as Auxiliary Electron Acceptor in Dye Sensitizer Molecules

AbstractDonor‐acceptor‐π bridge‐acceptor (D−A−π−A) motif dyes are promising dye sensitizers in dye‐sensitized solar cells (DSSCs). In this study, to strengthen with‐drawing electron force of the auxiliary electron acceptors(A) in D−A−π−A motif dye sensitizers, the metal complexes unit is be used as auxiliary electron acceptor(A) instead of organic electron‐withdrawing monomer. The four polymeric metal complexes were designed, synthesized, and characterized, which used metal complexes of phenanthroline derivatives as auxiliary acceptors (A), benzodithiophene‐dithiophene derivatives (BDTT) as donors (D), and 8‐hydroxyquinoline derivatives as π‐bridges and acceptors of the dye sensitizers, and have been used for dye sensitizers. Under AM 1.5 G (100 mW cm−2), the photovoltaic test results indicated that the short‐circuit photocurrent density (Jsc) of the DSSCs based four polymeric metal complexes are 11.26, 13.68, 14.42 and 15.57 mA cm−2and power conversion efficiency (PCE) are 5.96 %, 7.83 %, 8.07 %, 9.28 % respectively. BothJscandPCEvalue of the four polymeric metal complexes increased in order. This may be due to the fact that larger radius of metal ion under the same change number can enhance the coordination bond and cause stronger electron‐withdrawing ability of auxiliary acceptor and stronger charge‐transfer ability between the donor and the acceptor, which results in higherJscand higherPCEof the polymeric complex dye sensitizer.