Increase In Power Conversion Efficiency Research Articles

Managing interfacial properties of planar perovskite solar cells using Y3N@C80 endohedral metallofullerene

Fullerene derivatives have a wide range of applications in perovskite solar cells (PSCs), such as electron transport layers (ETLs), interfacial modifiers, and additives. However, there have been few studies of the use of endohedral metallofullerenes (EMFs) to improve the performance of PSCs. Here, a novel EMF (Y3N@C80) was synthesized and used as an interfacial modifier in PSC devices based on a SnO2 ETL. Energy level mismatches and detrimental carrier recombination have been observed in devices with a pristine SnO2 ETL, but these issues are alleviated with the assistance of Y3N@C80. A significant increase in open-circuit voltage from 1.106 V (SnO2) to 1.14 V (SnO2-Y3N@C80), an increase in power conversion efficiency from 20.59% to 21.66%, and a marked reduction in hysteresis were observed, which were attributed to the more suitable conduction band energy levels and more effective electron extraction at the SnO2-Y3N@C80/perovskite interface. In addition, the stability of the target devices was improved, which may be due to the hydrophobicity of Y3N@C80 and a reduction in trap states.

Fabrication and characterization of highly efficient dye-sensitized solar cells with composited dyes

As a representative of the next-generation solar cells, dye-sensitized solar cells (DSSCs) offer the efficient and ease of implementation of new technology for future energy supply. Herein, four commercially available dyes including, curcumin (C), betanin (B), crystal violet (CV), and methylene blue (MB), and their compositions were used as sensitizers for fabrication of titanium oxide photo-anode based DSSCs. All dyes were fully characterized using absorption and emission spectroscopy. Both DFT and TDDFT studies were also carried out to probe the electronic structure of these dyes. The power conversion efficiencies of each DSSCs prepared using the individual and composited dyes were measured and compared. Particularly, this is the first study to combine four different dyes for DSSCs, leading to a remarkable increase of power conversion efficiency. The DSSCs with combined curcumin, betanin, crystal violet, and methylene blue (in ratio 1:1:1:1 respectively) in ethanol exhibited the highest power conversion efficiency of 3.63%.

Halide exchange in the passivation of perovskite solar cells with functionalized ionic liquids

Applying additives to perovskite precursor solutions is an effective way to passivate perovskite films for the construction of perovskite solar cells (PSCs) with increased power-conversion efficiencies (PCEs) and enhanced stabilities. Ionic liquids (ILs) with halide anions have been applied as additives. Here, we report the application of imidazolium-based ILs, containing the nitrile functionality in the cation and chloride anion, as additives for triple-cation (Cs+, formamidinium [FA+], methylammonium [MA+]) PSCs. We found that a Cl-I exchange takes place between the I− anion of the triple-cation precursors and the Cl− anion of the IL. The fabricated PSCs containing perovskite films with the ILs show high PCEs (in the best case 22.86%) and high stabilities, with the unencapsulated devices retaining about 95% of their original efficiencies after 1,000 h. The mechanistic basis for the passivation effect of the IL additives in the perovskite films is described.

Enhancing the Intermolecular Interactions of Ladder-Type Heteroheptacene-Based Nonfullerene Acceptors for Efficient Polymer Solar Cells by Incorporating Asymmetric Side Chains

Enhancing the Intermolecular Interactions of Ladder-Type Heteroheptacene-Based Nonfullerene Acceptors for Efficient Polymer Solar Cells by Incorporating Asymmetric Side Chains

The lead-free perovskite solar cells with the green synthesized BiI3 and AgI nanoparticles using Vitex agnus-castus plant extract for HTM-free and carbon-based solar cells

A green BiI3 and AgI nanoparticles were synthesized using Vitex agnus-castus and then these nanoparticles were applied to obtain a high-quality methylammonium bismuth iodide ((CH3NH3I)3Bi2I9 = MBI) and AgBi2I7 as perovskite film. BiI3, MBI, and AgBi2I7 nanoperovskites have been proposed as viable candidates for concurrently resolving the instability and lead toxicity difficulties of unprecedented organic-inorganic hybrid halide perovskites. When the contact area between BiI3 and MBI and also AgI and BiI3 were increased due to the nanostructure of BiI3 and AgI, the reaction rate between BiI3 and methylammonium iodide (MAI) and also AgI and BiI3 was enhanced. Therefore, uniform and high crystalline perovskites layers without BiI3 residue was prepared. In this study, the vital role of the nanostructure perovskite layer in the stability and performance of the device is discussed.This resulted in a significant increase in power conversion efficiency (PCE), which reached 1.42%, as well as stability up to 7 days of AgBi2I7 solar cells against humidity, heat and light. Furthermore, without encapsulation, these devices exhibit superior tolerance under air conditions and high temperatures, providing new opportunities to promote the future development of lead-free AgBi2I7 nanoperovskites in the photoelectric field.

Recent Progress in Perovskite Materials Using Diammonium Organic Cations Toward Stable and Efficient Solar Cell Devices: Dion–Jacobson

Perovskite solar cells have been intensively studied recently due to their superb optoelectronic properties and rapidly increasing power conversion efficiency. However, perovskite solar cells with the AMX3 structure as the light‐absorbing layer have a big stability problem. Multiple alternatives have been developed to ensure their stability, such as dimensional engineering (2D and 2D/3D), which consists of the incorporation of large organic cations into the perovskite structure. Research in dimensional engineering has been prevalent in the Ruddlesden–Popper phases. The presence of this large cation slows the decomposition and improves the stability of perovskites. Thus, new 2D perovskites are being studied based on Dion–Jacobson (DJ) phases, consisting of the addition of diammonium cations and leading to the formation of 2D and 2D/3D perovskites with better stability due to their hydrogen bonding on both sides. Moreover, 2D DJ perovskites offer the advantage of decreasing the gap between layers with higher contacts, which improves not only their optoelectronic properties, but also their charge transport properties. This article begins with an overview of the crystal structure and optoelectronic characteristics of 2D perovskites. Then, the progress achieved currently in using DJ‐phase perovskites in photovoltaic is assessed. Finally, the possible research routes for producing low‐dimensional perovskites are highlighted.

Low-cost and easily prepared interface layer towards efficient and negligible hysteresis perovskite solar cells

Matched energy level alignment and minimal non-radiative recombination at the buried perovskite/charge transport material interface are essential for efficient electron transfer and highly-efficient perovskite solar cells (PSCs). Herein, we develop a facile and feasible method by inserting Cesium(I) Bis(trifluoromethanesulfonyl)imide (CsTFSI) interlayer to fabricate high performance PSCs with negligible hysteresis. With CsTFSI modification, tin oxide displays less trap density, improved electrical conductivity and better energy level alignment with perovskite, leading to a considerable increase in power conversion efficiency (PCE). Consequently, the champion target device presents a PCE of 22.05%, much higher than that of the control device (19.93%). Our work provides an effective and simple strategy for the modification of perovskite buried interface to obtain highly efficient PSCs.

FAPbI3 Perovskite Solar Cells: From Film Morphology Regulation to Device Optimization

Organic–inorganic hybrid perovskite solar cells (PSCs) have attracted great attentions due to their rapid increase of power conversion efficiency (PCE). Although the highest PCE of PSCs (25.7%) has been achieved via using formamidinium lead iodide (FAPbI3) with a suitable bandgap, there is still a lack of systematic analysis on FAPbI3‐based PSCs toward high stability and high efficiency. Herein, the progress in FAPbI3 films and achievements in their high‐efficiency and long‐term stability PSCs are comprehensively reviewed. First, the progress from the aspects of morphology, defect, dimension, and strain for FAPbI3 film optimization is summarized and then the development of FAPbI3 PSCs in both efficiency and stability is discussed. Then, the methods to improve the FAPbI3 film quality by morphology control, defect passivation, dimensional regulation, and strain engineering, as well as strategies to optimize the device structure and interface layers, which are critical to promote device stability and efficiency, are evaluated. Finally, the outlook and strategies for realizing commercialized FAPbI3 PSCs with high efficiency and long lifetime are discussed.

Reducing Photovoltaic Property Loss of Organic Solar Cells in Blade‐Coating by Optimizing Micro‐Nanomorphology via Nonhalogenated Solvent

AbstractBlade‐coating which is compatible with roll‐to‐roll (R2R) fabrication has been considered a promising technology for the large‐scale production of organic solar cells (OSCs). Despite the rapid increase in power conversion efficiency (PCE) of the devices, most processing solvents are still halogenated, which is a key issue that needs to be addressed urgently in commercialized manufacturing. In this work, targeted strategies are explored for the preparation of efficient OSCs via combining the nonhalogenated solvent toluene (TL) with blade‐coating. Based on the in situ UV–vis absorption, grazing‐incidence wide‐angle X‐ray scattering, and device performance measurements, the subtle relationship between processing solvents, film morphology, and properties is successfully established. The PM6:BTP‐eC9 blend film prepared by this strategy demonstrates higher crystallinity and smaller phase separation morphology, resulting in an outstanding PCE of 16.58% with low energy loss and high fill factor, which is higher than the CF‐based device (15.08%). Finally, the 1.00 cm2 device exhibits a high PCE of 14.82%, which is one of the highest values for OSCs prepared by blade‐coating based on TL solvent. This specific strategy combines blade‐coating with nonhalogenated solvent processing shows outstanding synergy in optimization of morphology, demonstrating excellent potential for the preparation of highly efficient large area OSCs.

Energy-harvesting photovoltaic transparent tandem devices using hydrogenated amorphous and microcrystalline silicon absorber layers for window applications

Transparent photovoltaic (TPV) tandem devices were prepared via plasma-enhanced chemical vapor deposition, using hydrogenated amorphous (a-Si:H) and microcrystalline (mc-Si:H) absorber layers that were sandwiched by transparent conducting oxide (TCO) electrodes. The high-performance TPV tandem devices were designed by controlling the film thickness of the mc-Si:H absorbers. For the TPV tandem devices with 300-nm-thick a-Si:H top cells, increasing the absorber thickness (tbottom) of mc-Si:H bottom cells from 1.0 to 2.1 μm induced an increase in power conversion efficiencies (PCEs) from 6.5% to 8.3% with a minor decrease in the average light transmittance from 16.6% to 14.6% at the 500–800 nm wavelengths. The TPV tandem devices exhibited JSC gains from 4.3 mA cm−2 (tbottom = 1.0 μm) to 0.5 mA cm−2 (tbottom = 2.3 μm) under bifacial illumination (front: 100 mW cm−2 and rear: 30 mW cm−2). This further resulted in additional PCE gains from 2.8% (tbottom = 1.0 μm) to 0.4% (tbottom = 2.3 μm), in comparison to the corresponding samples under front illumination only. The TPV tandem devices demonstrated excellent PV performance even at low-light illumination intensities (∼21 mW cm−2) in comparison to those at standard illumination light intensity (100 mW cm−2), while maintaining PCE values as high as 80%.

High-performance heptacyclic ladder-type heteroarene-based electron acceptors enabled by bulky neighboring side-chains and end-group fluorination

A banana-shape heptacyclic heteroarene core without sp 3 -hybridized bridging atoms is designed and synthesized for constructing novel nonfullerene acceptors. Through introducing bulky neighboring side-chains and fluorinated terminals, molecular aggregation and crystallinity of the nonfullerene acceptors can be effectively modulated, thus leading to improved charge transport and device performance. • Non-fullerene acceptors with sp 3 -hybridized-carbon-free skeletons are developed. • Bulky neighboring side-chains leads to acceptors with suitable aggregation. • End-group fluorination leads to a 6-fold increase in the efficiency of acceptor. • An “A-to-D” type J -aggregation is observed for the acceptor. Although ladder-type heteroarene building blocks without sp 3 -hybridized bridging atoms have been widely used for the synthesis of polymer donors, they have rarely been applied for constructing non-fullerene acceptors (NFAs) mainly due to the lack of strategies to effectively modulate self-aggregation and crystallinity of the resulting acceptors. Herein, a novel sp 3 -hybridized-carbon-free ladder-type skeleton, benzo[2,1-b:3,4-b']bis(4H-dithieno[3,2-b:2′,3′-d]pyrrole) featuring with two sets of neighboring side-chains, is designed and successfully synthesized as a donor core for developing NFAs ( cis -MH and cis -MF). The single-crystal result shows that the cis -MF forms slip-stacked J -type aggregates and packs in an anti-parallel “face-to-face” manner due to the bulkiness effect of neighboring side-chains. This molecular stacking mode effectively prevents the formation of oversized aggregates in the corresponding active layer as evidenced by atomic force microscopy analyses. Introduction of the fluorinated terminals broadens the absorption range and increases the crystallinity of the acceptor, thus greatly promoting its carrier transport. As a result, the cis -MF-based device exhibits a 6-fold increase in power conversion efficiency compared to the cis -MH-based device. Overall, this work provides a new molecular design strategy as well as a novel sp 3 -hybridized-carbon-free ladder-type building block for developing efficient NFAs that can be used to further advance the PCEs of polymer solar cells.

Practical Enhancements in Current Density and Power Generation of Bifacial Semitransparent Ultrathin CIGSe Solar Cells via Utilization of Wide Bandgap Zn-Based Buffer.

Among many building‐integrated semitransparent photovoltaics (BISTPVs), semitransparent ultrathin (STUT) Cu(Inx,Ga1‐x)Se2 (CIGSe) solar cells are distinguishable due to their potential high power conversion efficiency (PCE) among other thin‐film solar cells, versatile applicability based on thin film deposition processes, high stability consisting of all inorganic compositions, and practical expandability to bifacial applications. However, the fundamental trade‐off relationship between PCE and transparency limits the performance of BISTPV because implementing a higher semitransparency lowers the optical budget of incoming light. To expand the available optical budget and to enhance the PCE while maintaining a suitable transparency in STUT CIGSe solar cell with single‐stage coevaporated 500‐nm‐thick absorber, an atomic layer deposited wide bandgap Zn(O,S) buffer is introduced as the replacement of conventional CdS buffer, which partially limits incoming light less than 520 nm in wavelength. As a replacement result, more incoming light becomes valid for power conversion, and the short circuit current density (J sc) has increased comparatively by 17%, which has directly lead to a large increase in PCE up to 12.41%. Furthermore, Zn(O,S) buffer in the STUT CIGSe solar cell also has enhanced the bifacial compatible efficiency (BCE), which has increased to 14.44% at 1.3 sun and 19.42% at 2.0 sun.

Effect of Ga1-xInxAs1-yPy Al-free asymmetric barrier on GaAs-based 808-nm laser diode.

A GaInAsP/GaAs/GaAsP Al-free laser with asymmetric potential barriers is designed theoretically to prevent carrier leakage. The band alignment demonstrates that a high height of the potential barrier decreases the leakage current. The internal quantum efficiency increases by increasing the injection efficiency, which is attributed to the decreasing electron potential barrier heights. Moreover, the threshold current and operating voltage decrease by adopting a novel barrier so that the output power and power conversion efficiency (PCE) increase. When the injection current is 5 kA/cm2, the PCE is 77.82% and the output power is 13.21W. The physical mechanism of potential barrier heights affecting carrier transport is investigated, which will provide a theoretical basis for optimizing laser diodes.

Thermo-Optical and Structural Studies of Iodine-Doped Polymer: Fullerene Blend Films, Used in Photovoltaic Structures.

Optical and structural properties of a blend thin film of (1:1 wt.) of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) doped with iodine (I2) and then exposed to a stepwise heating were reported and compared with the properties of doped P3HT films. The UV-Vis(T) absorption measurements were performed in situ during annealing runs, at the precisely defined temperatures, in a range of 20–210 °C. It was demonstrated that this new method allows one to observe the changes of absorption spectra, connected with the iodine release and other structural processes upon annealing. In addition, the thermally-induced changes of the exciton bandwidth (W) and the absorption edge parameters, i.e., the energy gap (EG) and the Urbach energy (EU) were discussed in the context of different length of conjugation and the structural disorder in polymers and blends films. During annealing, several stages were distinguished and related to the following processes as: the iodine escape and an increase in P3HT crystallinity, the orderly stacking of polymer chains, the thermally inducted structural defects and the phase separation caused by an aggregation of PCBM in the polymer matrix. Moreover, the detailed X-ray diffraction studies, performed for P3HT and P3HT:PCBM films, before and after doping and then after their thermal treatment, allowed us to consider the structural changes of polymer and blend films. The effect of iodine content and the annealing process on the bulk heterojunction (BHJ) solar cells parameters was checked, by the impedance spectroscopy (IS) measurements and the J-V characteristics registration. All of the investigated P3HT:PCBM blend films showed the photovoltaic effect; the increase in power conversion efficiency (PCE) upon iodine doping was demonstrated.

Thermal and optical performance characterization of bare and phosphor converted LEDs through package level immersion cooling

Increased demand for high flux electronics requires creative and affordable thermal management approaches to meet the performance and lifetime expectations. In the present study, optical and thermal improvements of a new package level liquid coolant encapsulation that directly targets heat generation zones are studied for bare and phosphor converted LEDs. As heat both at chip and phosphor composite regions are being generated, a series of detailed experimental and theoretical characterization is performed in order to examine the capability of the new cooling method. The findings can be used to extend the application of precisely controlled liquid packing on the heat source region of optoelectronic components. This method has shown a 15% reduction in thermal resistance and a 7% increase in power conversion efficiency of LED packages. The capacity of this method is mainly limited to the thermal conductivity of the coolant while a significant ability for improvement can be expected by utilizing thermally conductive particles such as hexagonal boron nitride inside the coolant.

The Subtle Structure Modulation of A2 -A1 -D-A1 -A2 Type Nonfullerene Acceptors Extends the Photoelectric Response for High-Voltage Organic Photovoltaic Cells.

Molecular structural modifications are utilized to improve the short-circuit current (JSC ) of high-voltage organic photovoltaics (OPVs). Herein, the classic non-fullerene acceptor (NFA), BTA3, is chosen as a benchmark, with BTA3b containing the linear alkyl chains on the middle core and JC14 fusing thiophene on the benzotriazole (BTA) unit as a contrast. The photovoltaic devices based on J52-F: BTA3b and J52-F: JC14 achieve wider external quantum efficiency responses with band edges of 730 and 800nm, respectively than that of the device based on J52-F: BTA3 (715 nm). The correspondingJSC increases to 14.08 and 15.78mA cm-2 , respectively, compared to BTA3 (11.56mA cm-2 ). The smaller Urbach energy and higher electroluminescence efficiency guarantee J52-F: JC14 a decreased energy loss (0.528eV) and a high open-circuit voltage (VOC ) of 1.07V. Finally, J52-F: JC14 combination achieves an increased power conversion efficiency (PCE) of 10.33% than that of J52-F: BTA3b (PCE = 9.81%) and J52-F: BTA3 (PCE = 9.04%). Overall, the research results indicate that subtle structure modification of NFAs, especially introducing fused rings, is a simple and effective strategy to extend the photoelectric response, boosting theJSC and ensuring a high VOC beyond 1.0V.

Importance of tin (II) acetate additives in sequential deposited fabrication of Sn-Pb-based perovskite solar cells

Sn-Pb-based perovskite is a promising solar cell material for its low toxicity and narrow band gap. However, the poor crystallinity of Sn-containing perovskite films and the facile oxidation of Sn2+ are obstacles to the efficiency and stability of Sn-Pb-based perovskite solar cells (PSCs). Herein, we developed a new additive strategy of tin acetate (SnAc2) to fabricate high-quality (HC(NH2)2)n(CH3NH3)1-nPb0.7Sn0.3IxBr3-x films by a two-step method and simultaneously restrict the oxidation of Sn2+ to Sn4+ by coordination between Sn2+ and Ac-. Moreover, SnAc2 built an Sn-rich environment to alleviate the intrinsic Sn2+ vacancies. All these effectively reduced the defect state densities and carrier nonradiative recombinations in the device, resulting in improvements in the performance of PSCs. The PSCs with the SnAc2 additive exhibited a increase in average power conversion efficiency (PCE) from 15.60% to 16.69%. Furthermore, the phenethylammoniumiodide (PEAI) post-treatment was introduced to passivate the SnAc2-containing perovskite films. Finally, the optimal cell with a PCE of 17.93% was obtained, which was second-best compared to the reported Sn-Pb-based PSCs by the two-step methods. Furthermore, the producibility and stability of devices are also improved due to the inhibited oxidation of Sn2+ by SnAc2 additives and the protection of two-dimensional (2D) (PEA)2PbI4 perovskites, the unencapsulated PSC maintained 80.4% of its initial efficiency when stored in air after 24 days.

Symmetry-Breaking Charge Separation in Molecular Constructs for Efficient Light Energy Conversion

The generation of electron–hole radical pair at the active layer of organic photovoltaics through symmetry-breaking charge separation (SB-CS) has a crucial role in enhancing open-circuit voltage (Voc) and thereby increasing power conversion efficiency. Since the SB-CS materials achieve intramolecular charge separation with a negligible energetic driving force and decelerated charge recombination (CR) rate, SB-CS has been subjected to extensive experimental and theoretical studies. This Focus Review assesses the fundamentals of photosynthetic reaction centers, especially the “special pair”, and discusses how covalent control over the geometric arrangement, surrounding dielectric medium, and substitutions on multichromophoric perylenediimide architecture affects the energy landscape of SB-CS and CR. We systematically summarize the kinetically favored undesirable radiative and non-radiative deactivation channels of SB-CS and CR processes on diverse chromophoric arrangements. Here, we suggest new rational design principles to fine-tune the electron-transfer dynamics at the molecular level to improve the performance of light–energy conversion devices.

Challenges for Thermally Stable Spiro-MeOTAD toward the Market Entry of Highly Efficient Perovskite Solar Cells.

Perovskite solar cells (PSCs) have drawn great attention because they have seen a dramatic increase in power conversion efficiency (PCE) over only a decade and reached 25.5% of certified PCE in 2021. The efficiency competitiveness with a low production cost puts up PSCs as a candidate for next-generation photovoltaics, encouraging the stability assessment. Research on PSCs, however, still struggles with the stability issue, particularly at elevated temperature, which is mainly ascribed to the use of spiro-MeOTAD as a hole transport material (HTM). Though many attempts have been made to explore a new HTM to replace spiro-MeOTAD, the improved stability is mostly obtained at the expense of losing efficiency. Likewise, the question of the effectiveness of alternatives for spiro-MeOTAD consistently remains. In this perspective, the morphological stability of spiro-MeOTAD at elevated temperatures is discussed to determine the underlying origins of the thermal stability issue and find feasible strategies to resolve it.

Performance-Enhancing Sulfur-Doped TiO2 Photoanodes for Perovskite Solar Cells

High-performance electron transport layer (ETL) anode generally needs to form a uniform dense layer with suitable conduction band position and good electron transport properties. The TiO2 photoanode is primarily applied as the ETL because it is low-cost, has diverse thin-film preparation methods and has good chemical stability. However, pure TiO2 is not an ideal ETL because it lacks several important criteria, such as low conductivity and conduction band mismatch with compositional-tailored perovskite. Thus, TiO2 is an inefficient photo-anode or ETL for high-performance perovskite devices. In this study, sulfur as dopant in the TiO2 photo-anode thin film is used to fabricate solid-state planar perovskite solar cells in relatively high humidity (40–50%). The deposited S-doped thin film improves the power conversion efficiency (PCE) of the device to 6.0%, with the un-doped TiO2 producing a PCE of 5.1% in the best device. Improvement in PCE is due to lower recombination and higher photocurrent density, resulting in 18% increase in PCE (5.1–6.0%).