Enhanced Power Conversion Efficiency Research Articles

Simple benzothiadiazole-based small molecules as additives for efficient organic solar cells

Multiple strategies have been developed to improve the photovoltaic performance of organic solar cells (OSCs) by fine-tuning the morphology of the active layers, such as introducing functional third components, taking post-treatments and so on. In this work, a series of non-volatile solid additives BT, BTOR, BT2F, BTNO2(2 + 6), and BTNO2(6) were synthesized, by introducing substituent groups into benzothiadiazole units, and the thermal stability, optical and electrochemical properties were systematically studied. These additives were applied to further investigate the effect on the photovoltaic performance of OSCs. The results show that these additives could effectively promote exciton dissociation and charge transfer, reduce bimolecular recombination, and optimize the morphology of the active layer. Significantly, the PBDB-T:ITIC-based devices processed with BT achieved a power conversion efficiency (PCE) of 11.57%, increased by 17% compared to the as-cast devices due to the high and balanced carrier mobility. Enhancement of PCE proved the feasibility of the application of non-volatile solid additives in the non-fullerene-based binary system.

Tailoring Anchoring Groups in Low‐Dimensional Organic Semiconductor‐Incorporated Perovskites

Low‐dimensional, organic semiconductor‐incorporated perovskites (OSiPs) are hybrid structures with functional organic cations intercalated between inorganic octahedron frameworks. They exhibit increased structural and compositional tunability, fascinating electronic properties, and enhanced stability for a wide range of applications. Currently, the interactions between the conjugated organic building blocks and the metal halide inorganic building blocks have not been fully investigated. Herein, a series of bithiophene‐based conjugated ligands with formamidinium, imidazolium, and benzimidazolium terminal groups to examine the influence of different anchoring groups on the crystal structures, phase formation, and device performances are reported. It is shown that the terminal groups of the ligands have significant effect on the interactions between ligands and octahedra in perovskites, thus determine the formation of the crystal structures. Only the 3D perovskite solar cells passivated by the ligands with imidazolium and benzimidazolium terminal groups exhibit enhancement in power conversion efficiencies as well as reduced hysteresis. A new strategy is provided for designing novel OSiPs structures and functionalities via tailoring the anchoring group.

Outdoor performance evaluation of a novel photovoltaic heat sinks to enhance power conversion efficiency and temperature uniformity

The non-uniformity of photovoltaic (PV) temperature can further deteriorate its power conversion efficiency and technical lifetime over long field exposures. This study proposed novel fins for a PV module temperature reduction and enhancing temperature uniformity. The proposed multi-level fin heat sinks (MLFHS) consist of a novel geometry of extruded aluminum material attached to the rear side of the PV module. The developed outdoor experimental setup consists of two identical 120 Wp monocrystalline PV modules; one served as a reference module for comparison against the module with the proposed novel heat sink geometry. The temperature distributions across PV modules and the electrical parameters were then recorded and analysed. A substantial drop in the module temperature of 8.45 °C was observed at solar irradiance and ambient temperature of 941 W/m2 and 36.17 °C, respectively. As a result, the heat sink improved the overall power output up to 9.56% under outdoor operating conditions. Furthermore, the prominent effect of temperature uniformity was perceived for solar irradiance greater than 600 W/m2 and improved by 14.8%. These findings are foundational for passive cooling methodologies to guide further research and development of an efficient PV cooling methodology.

Investigation of silver nanowires in Zn2SnO4 spheres for enhanced dye-sensitized solar cells performance

In this paper, 1-D Ag nanowires (AgNW) have been integrated into zinc tin oxide (Zn2SnO4) spheres using a simple one-step hydrothermal synthesis to enhance power conversion efficiency (PCE). Two different amounts of Ag nanowires were applied to assemble a series of dye-sensitized solar cells (DSSCs) and the photovoltaic performance was evaluated. UV–VIS absorption spectra, Mott-Schottky and electrochemical impedance spectroscopy studies demonstrated that the addition of AgNWs can enhance the photoelectrochemical activity and charge injection. We found that 200 µL of AgNW has significantly increased JSC and VOC from 2.0 to 3.83 mA/cm2 and 709–760 mV, respectively, compared to the pure DSSC based on Zn2SnO4.

Sequential growth-controlled silver selenide nanoparticles embedded 1D-CdS nanowires: Heterostructure design to enhance power conversion efficiency

Room temperature sequential growth namely, successive ionic layer adsorption and reaction (SILAR) method has been successfully processed towards the controlled growth of silver selenide (Ag2Se) nanoparticles onto one dimensional (1D) CdS nanowires (NWs) array. Well controlled size tuning enables well-aligned heterostructure yielding almost four times enhancement (0.34%) in power conversion efficiency compared to the bare CdS NWs (0.09%) in photoelectrochemical (PEC) solar cell assembly. Results are well equipped through structural, surface morphological, optical and elemental oxidation state in correlation with PEC solar cell, external quantum efficiency (EQE), Mott-Schottky (M − S), and electrochemical impedance spectroscopy (EIS) performances. Interestingly, sequential SILAR method produces extremely conformal coverage of Ag2Se layer with precise thickness control. The optimum mutualistic contribution from Ag2Se and CdS not only broaden the light absorption range but also allows the rapid separation of excited charge carriers at heterostructure interface.

A self-arranged metal–organic polyhedron/fullerene asymmetric structure improves the performance of inverted perovskite solar cells

A hybrid dirhodium tetracarboxylate-based metal–organic polyhedron (MOP):PCBM electron transport layer is demonstrated to give rise to a 9% enhancement in power conversion efficiency for the derived inverted perovskite solar cell.

Polymerized Small‐Molecule Acceptor as an Interface Modulator to Increase the Performance of All‐Small‐Molecule Solar Cells (Adv. Energy Mater. 3/2022)

Organic Solar Cells In article number 2102394, Dan Deng, Xiaohui Qiu, Zhixiang Wei and co-workers introduce a polymerized small-molecule acceptor into all-small-molecule organic solar cells as an interface modulator. An enhanced power conversion efficiency over 15% is achieved by improved charge transportation and condensed morphology. This work provides useful guidance for the interface modulator strategy in organic solar cells.

Ionic and poly(ionic liquid)s as perovskite passivating molecules for improved solar cell performances

Ionic liquids and poly(ionic liquid)s act as bulk and/or passivation agents when used as additives in methylammonium-free lead perovskites, leading to devices showing enhanced power conversion efficiencies, reduced hysteresis and improved stability.

Improved reproducibility of carbon-based cesium/formamidinium perovskite solar cells via double antisolvent drippings in adduct approach

High-quality perovskite materials are usually prepared in a non-reactive environment, which increases fabrication costs and poses difficulties in mass production. In this work, the deposition of cesium/formamidinium (CsFA) perovskite under low-cost dry-air conditions was modified to improve both material quality and photovoltaic performance. By using double chlorobenzene drippings in the adduct approach, pinhole-free and smooth CsFA films were achieved. The carbon-based perovskite solar cells (PSCs) using the obtained CsFA films provided an enhanced power conversion efficiency (PCE) with good reproducibility. The main reasons for this achievement are the suppression of charge recombination caused by traps in the perovskite films and the improvement of interface properties. In addition, our proposed method was found to be applicable for reproducible 1 cm × 1 cm solar modules. Our findings open up the possibility for low-cost, simple, and large-scale manufacturing of perovskite-based optoelectronic devices. • A modified CsFA deposition method for dry air conditions was proposed. • By using double antisolvent drippings in the adduct approach, the quality of CsFA films was improved. • The pinhole-free and flat CsFA device achieved an efficiency of 13.12% with good reproducibility. • The introduced method is also applicable for reproducible 1 cm 2 -area PSCs.

Highly efficient layer-by-layer large-scale manufacturing of polymer solar cells with minimized device-to-device variations by employing benzothiadiazole-based solid additives

Benzothiadiazole-based solid additives have been designed as morphology controllers leading to enhanced power conversion efficiency and reduced device-to-device variations in small- and large-areas single cells.

In Situ Graded Passivation via Porphyrin Derivative with Enhanced Photovoltage and Fill Factor in Perovskite Solar Cells

While perovskite solar cells (PSCs) have recently experienced a rapid rise in power conversion efficiency (PCE), the prevailing PSCs still contain nondesirable defects in the interior and interface of the perovskite layer, which limits further enhancement in PCE and device stability. Herein, a new D–π–A‐type zinc pyridine porphyrin derivative (ZnPP) is synthesized and used as a passivation molecular via the antisolvent process for modifying the typical perovskite bulk thin film, leading to a new type of PSC with a graded passivation of the perovskite layer. Impressively, it is found that ZnPP treatment significantly improves the quality of perovskite films and reduces charge transport losses through passivating the uncoordinated Pb2+ cations, yielding devices with a high efficiency of 21.08% with fill factor (FF) of 82.91% and demonstrating the promise of integration of perovskite bulk thin films with tailor molecular via graded modification.

Bandgap Tuning and Input Parameter Optimization for Lead‐Free All‐Inorganic Single, Double, and Ternary Perovskite‐Based Solar Cells

A comprehensive device performance optimization of perovskite solar cells (PSCs) having the device configurations FTO/IGZO/CsSn0.5Ge0.5I3/CuO/Au, FTO/IGZO/Cs4CuSb2Cl12/CuO/Au, and FTO/IGZO/Cs3Bi2I9/CuO/Au containing the single, double, and ternary perovskites CsSn0.5Ge0.5I3, Cs4CuSb2Cl12, and Cs3Bi2I9, respectively, is done utilizing the SCAPS 1D tool. The bandgap tuning of the perovskite layers and the work function optimization of the rear‐contact metals for the chosen device designs provide an enhanced power conversion efficiency of 23.15%, 17.39%, and 9.75% for the solar cell architecture with the light‐captivating layers CsSn0.5Ge0.5I3, Cs4CuSb2Cl12, and Cs3Bi2I9, respectively. Herein, it is identified the variation of electron affinity of the perovskite layer for the aforementioned device configurations does not produce any significant enhancement in the output parameters of the simulated configurations.

Front Cover: Efficiency‐Enhanced Scalable Organic Photovoltaics Using Roll‐to‐Roll Nanoimprint Lithography (ChemSusChem 2/2022)

The Front Cover shows the development of Roll-to-Roll (R2R) light-management foils integrated into fully scalable non-fullerene acceptor (NFA)-based organic photovoltaics (OPV) to enhance light absorption in, and power conversion efficiency of, the solar cells. The R2R light-management foils are demonstrated to provide a 25% enhancement in power conversion efficiency enhancement for the NFA OPV, demonstrating that this may be a viable route for boosting the performance of industrial OPV in the future. More information can be found in the Full Paper by M. A. Yakoob et al.

Charge carrier dynamics and photovoltaic properties of near-infrared absorbing squaraine incorporated solution-processed additive-free PTB7:PCBM based ternary solar cells

The introduction of a third component vehemently modifies the morphology and charge carrier dynamics in the blend of a donor–acceptor pair, thereby affecting the photovoltaic properties of organic solar cells (OSCs). Combining steady-state, impedance, and transient spectroscopic measurements, photovoltaic properties of 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (SQ) incorporated additive-free PTB7:PC70BM OSCs are assessed. As observed from steady-state measurements, concomitant enhancement in open-circuit voltage (VOC) and short-circuit current density (JSC) has caused a 33% enhancement in power conversion efficiency (PCE) with good reliability and reproducibility. On introducing 25 wt.% SQ to the OSCs, V OC has increased from 0.74 to 0.80 V, while J SC has improved from 11.3 to 13.9 mA cm−2 with an increment in exciton dissociation probability rate from 81.5% to 94.9%. However, the fill factor values show inconsistent marginal variations with SQ addition. Equivalent circuit modeling of bias-voltage dependent impedance spectra along with transient photovoltage measurements reveal an improvement in effective charge carrier lifetime for the SQ incorporated OSCs, in comparison to the binary device. The addition of SQ also ensures better charge transport and extraction, as evidenced by photo-CELIV and transient photocurrent analysis. Atomic force microscopy (AFM) images confirm the effective tuning of the morphology of the active layer when SQ is introduced into the binary blend, favoring efficient charge dissociation and transport. The possible operation mechanism of SQ incorporated ternary OSCs is proposed based on photoluminescence and AFM measurements. Moreover, the un-encapsulated OSC with 25 wt.% SQ has retained 91% of the initial PCE, while for the binary device the PCE declined to ∼75% of the initial value after 200 h of continuous 1 sun illumination from a white LED in ambient atmosphere.

β-Diketone Coordination Strategy for Highly Efficient and Stable Pb-Sn Mixed Perovskite Solar Cells.

The narrow bandgap Pb-Sn hybrid perovskite materials with lower toxicities and adjustable optical bandgaps provide the opportunity to construct high-efficiency perovskite solar cells (PerSCs). To solve the issues of the uncontrollable crystallization rate of Pb-Sn perovskite and easy oxidation of Sn2+, a β-diketone-based additive, N,N,N',N'-tetraphenylmalondiamide (TPMA), is introduced to coordinate with Pb2+ and Sn2+. The introduction of TPMA can improve the morphology of perovskite films and decrease the density of defect states, resulting in an enhanced power conversion efficiency of >20% and improved stability. The PerSC without encapsulation retains 94% of its initial efficiency after being stored for 1000 h in a nitrogen-filled glovebox and shows a lifetime of only 8% degradation after being continuously heated for 100 h at 80 °C. This work represents a new strategy of introducing a β-diketone ligand as an additive in precursor engineering for achieving efficient and stable PerSCs.

Nanoscale heterogeneous distribution of surface energy at interlayers in organic bulk-heterojunction solar cells

<h2>Summary</h2> Surface energy of the underneath interlayer plays a crucial role in determining the morphology of bulk-heterojunction (BHJ) film in solution-processed organic solar cells (OSCs). However, little attention has been paid to this perspective at the microscopic level. In this study, we demonstrate an effective strategy to tune the nanoscale heterogeneous distribution of surface energy (HeD-SE) at interlayers through incorporating two-dimensional (2D) MoS₂ nanosheets, which modulate the component distribution, molecular orientation, and phase separation in the upper BHJ layers, leading to suppressed charge recombination and increased charge extraction in devices with enhanced power conversion efficiency (PCE) and device stability. Furthermore, we explore the relationship among the different surface energies of BHJs between the donor and the acceptor, the nanoscale HeD-SE at interlayers, and the PCEs of the resultant devices. This work reveals the impact of nanoscale heterogeneity in the distribution of surface energy in the underneath interlayers on the BHJ morphology and device performance in OSCs.

The emergence of concentrator photovoltaics for perovskite solar cells

The emergence of high-efficiency photovoltaic research is undergoing intense study and is technologically desirable to meet sustainable energy and environmental demand. However, every single solar cell has a theoretical power conversion efficiency limit, and, thus, without compromising the cost, the power conversion efficiency enhancement of a solar cell is highly challenging. As a convenient solution, concentrating photovoltaics can focus sunlight onto an extremely high-efficiency solar cell integrating various optics. Concentrating photovoltaics use optical devices that collect and redirect the light toward the smaller photovoltaic cell and reduce the demand for the mined elements required for the solar cell fabrication. The research interest from the photovoltaic community has concentrated on organic-inorganic hybrid halide perovskite absorbers, and nowadays, perovskite solar cells manifest their outstanding contribution among the low-cost photovoltaic technologies. Inevitably, large-area perovskite solar cells suffer a lot with their poor stability, hindering their commercialization pace. Thus, the implementation of concentrating photovoltaic technology in perovskite solar cells demonstrates an inherent advantage using a smaller size solar cell. This review provides an overview of concentrating photovoltaic technology implementation, including their recent research and development portfolio, their economic benefits in combination with inexpensive optical elements and tracking systems, limitations, challenges, and relative scope of the future study, focusing on the emerging perovskite solar cell technology.

Dipole Engineering of Two-Dimensional van der Waals Heterostructures for Enhanced Power-Conversion Efficiency: The Case of Janus Ga2SeTe/InS

Highly efficient separation of tightly bound excitons (photoinduced electron-hole pairs) at an interface is crucial for high-performance two-dimensional (2D) heterostructure solar cells. Here we propose and demonstrate a strategy---dipole engineering---to effectively separate excitons at a 2D interface, which could evidently enhance power-conversion efficiency (PCE) via Heyd-Scuseria-Ernzerhof density functional calculations. The proposed dipole engineering is based on the synergetic effect of the intrinsic dipole in 2D Janus materials and interface dipole caused by charge transfer at the interface of 2D van der Waals heterostructures, in stark contrast to those strategies previously used, such as applying a strain or electric field. Taking the Janus ${\mathrm{Ga}}_{2}\mathrm{Se}\mathrm{Te}/\mathrm{In}\mathrm{S}$ heterostructure as an example, we demonstrate that the PCE can be promoted to a peak value of 23.2% when the intrinsic and interface dipoles are in the same direction, when accompanied by an appropriate applied compression strain. In addition, the Janus heterostructure possesses suitable band-edge positions of redox reaction potentials for full water splitting. Our work may herald an intrinsic yet effective way for enhancing the performance of optoelectronic devices, in contrast to the conventional external stimuli strategy.

Aminosilicate modified zinc oxide Nanorod-GO nanocomposite for DSSC photoanodes

Amine-functionalized ZnO nanorods@graphene oxide (ZnO-NR/NH2/GO) nanocomposites prepared by a facile solution route have been investigated through X-ray diffraction, diffuse reflectance spectra, Raman spectra, scanning electron microscopy and transmission electron microscopy. The amine-functionalized ZnO-NR/NH2/GO-2 nanocomposite exhibits very strong visible light absorption. Dye-sensitized solar cell (DSSC) made of ZnO-NR/NH2/GO-2 nanocomposite (with optimum 2 wt % GO) photoanode delivers a power conversion efficiency (PCE) of 3.76% which is much higher than the efficiency of unmodified ZnO-NR/GO photoanodes based DSSC (2.27%). The enhancement of PCE is primarily caused by the increased current density, attributed to the incorporation of aminosilicate and GO on the surface of ZnO-NRs which facilitates rapid transfer of electron from conduction band of ZnO to conducting surface of FTO. This diminished recombination of photogenerated electrons and holes improve the electron transfer at the photoanode/electrolyte interfaces.

Embedded current collectors for efficient large area perovskite solar cells

Perovskite solar cells (PSCs) are an emerging solar cell technology that has shown the fastest growth in power conversion efficiency (PCE). The present power conversion efficiency record of 25.5% is already comparable to crystalline silicon technology, which is attracting the research and industrial community attention. The main challenges in scaling-up PSCs are the limited conductivity of the transparent electrode and the difficulty in depositing an uniform and defect-free perovskite layer over large areas. This work reports the use of engraved gold metal lines in the FTO glass substrate for increasing its electronic conductivity; the prepared 5 cm2 PSC displays a PCE enhancement of 26% over the cells prepared with pristine FTO substrates.