Conversion Efficiency Of Solar Cells Research Articles

Reducing Parasitic Loss and Deep Defect Formation via Copper Doping Toward Highly Efficient Sb2Se3 Solar Cells

AbstractAntimony selenide (Sb2Se3) has great potential as a light‐absorbing layer in thin‐film photovoltaics because of its excellent photoelectric properties and superior stability. Presently, high‐efficiency Sb2Se3 solar cells use a heterojunction consisting of a p‐type Sb2Se3 absorber and an n‐type CdS layer. The power conversion efficiency (PCE) of Sb2Se3 solar cells is restricted by the low carrier concentration in the CdS layer, complex intrinsic deep defects of Sb2Se3, and unsuitable energy level band alignment in the junction. This paper presents a copper (Cu) doping strategy that achieves a synergistic doping effect, enabling controllable doping in both the n‐type CdS layer and p‐type Sb2Se3 absorber. First, proper Cu doping significantly enhances the short‐wavelength transmittance of CdS films and increases their n‐type carrier concentration. The Vbi in the CdS/Sb2Se3 heterojunction improves from 521 to 751 mV. Second, a post‐annealing process is performed to facilitate Cu diffusion from the CdS layer to the Sb2Se3 absorber. This approach successfully passivates intrinsic deep defect E2 and reduces the interfacial trap‐assisted nonradiative recombination losses. As a result, the Cu‐doped Sb2Se3/CdS solar cell presents a PCE of 10.23%, representing a 40% enhancement in PCE compared to the undoped CdS/Sb2Se3 heterojunction device.

Enhancing charge carrier dynamics with an N-type polymer guest for printable ternary organic solar modules

The ternary strategy offers a promising route to enhance the power conversion efficiencies (PCEs) of organic solar cells (OSCs). In this contribution, we focus on the state-of-the-art binary system PM6:L8-BO and reveal how the n-type polymer guest (PYIT) in the PM6:L8-BO:PYIT ternary system enhances carrier dynamics, thereby improving both efficiency and scalability for large-area printable OSC modules. These benefits are primarily attributed to two key factors: (i) the excellent miscibility of the PYIT guest with the host materials, coupled with the chain-dominant structure and high crystallinity nature of the PYIT polymer, which creates additional pathways for carrier transport and charge transfer; (ii) the incorporation of PYIT, which limits the excessive aggregation of L8-BO, improves molecular packing, and reduces film defects, thereby enhancing exciton dynamics. These optimizations lead to an increase in PCEs from 17.58% in the binary system to 18.59% in the ternary OSC, with improvements across all photovoltaic parameters. More importantly, the PM6:L8-BO:PYIT ternary system exhibits excellent compatibility with large-area printing processes, as demonstrated by a doctor blading OSC module achieving 15.57% PCE over an area of 11.7 cm2. This work highlights the potential of the ternary methodology in tuning the physical properties of OSCs while enhancing both performance and scalability.

Mitigating the Efficiency Deficit in Single-Crystal Perovskite Solar Cells by Precise Control of the Growth Processes.

The power conversion efficiencies (PCEs) of polycrystalline perovskite solar cells (PC-PSCs) have now reached a plateau after a decade of rapid development, leaving a distinct gap from their Shockley-Queisser limit. To continuously mitigate the PCE deficit, nonradiative carrier losses resulting from defects should be further optimized. Single-crystal perovskites are considered an ideal platform to study the efficiency limit of perovskite solar cells due to their intrinsically low defect density, as demonstrated in bulk single crystals. However, current single-crystal perovskite solar cells (SC-PSCs) based on single-crystal thin film (SCTF) suffer from severe nonradiative carrier losses at the interface and in the bulk simultaneously due to the immature SCTF growth techniques. In this study, we show that the SC-PSCs can outperform state-of-the-art PC-PSCs, with MAPbI3 as an example, by suppressing carrier losses at the interface and in the bulk in device-compatible SCTFs through precisely controlling their growth.

A High Throughput Platform to Minimize Voltage and Fill Factor Losses

AbstractOrganic photovoltaics (OPV) now can exceed 20% power conversion efficiency in single junction solar cells. To close the remaining gap to competing technologies, both fill factor and open‐circuit voltage must be optimized. The Langevin reduction factor is a well‐known concept that measures the degree to which charge extraction is favored over charge recombination. It is therefore ideally suited as an optimization target in high‐throughput workflows; however, its evaluation so far requires expert interaction. Here, an integrated high‐throughput workflow is presented, able to obtain the Langevin reduction factor within a few seconds with high accuracy without human intervention and thus suited for autonomous experiments. This is achieved by combining evidence from UV–vis spectra, current–voltage curves, and a novel implementation of microsecond transient absorption kinetics allowing, for the first time, the intrinsic determination of charge absorption cross‐sections, which is crucial to reporting stationary charge densities. The method is demonstrated by varying the donor:acceptor ratio of the high performance OPV blend PM6:Y12. The high reproducibility of the method allows to find a strictly exponential relationship between the PM6 exciton energy and the Langevin reduction factor.

Evolution of Two-Dimensional Perovskite Films Under Atmospheric Exposure and Its Impact on Photovoltaic Performance.

Two-dimensional (2D) Ruddlesden-Popper perovskites (RPPs) have garnered significant attention due to their enhanced stability compared with their three-dimensional counterparts. However, the power conversion efficiency (PCE) of 2D perovskite solar cells (2D-PSCs) remains lower than that of 3D-PSCs. Understanding the microstructural evolution of 2D perovskite films during fabrication is essential for improving their performance. This study demonstrates that exposing bare 2D perovskite films to the atmosphere during device fabrication can significantly enhance the PCE of 2D-PSCs. The performance improvement is primarily attributed to the gradual evaporation of organic butylammonium (BA+) spacer cations from the film as butylamine (BA) gas. This evaporation refines the film's composition and structure, leading to the spontaneous formation of larger-n phase RPPs, which exhibit superior carrier mobility. Consequently, the PCE of 2D-PSCs is enhanced. This work offers new insights into the structural evolution of 2D RPP films under ambient conditions and provides a feasible strategy for optimizing the performance of 2D-PSCs and other optoelectronic devices.

Construction of Linear Tetramer-Type Acceptors for High-Efficiency and High-Stability Organic Solar Cells.

Thanks to the development of non-fullerene acceptor (NFA) materials, the photovoltaic conversion efficiency (PCE) of organic solar cells (OSCs) has exceeded 20 %, which has met the requirements for commercialisation. In the current stage, the main focus is to balance the performance and stability. It has been shown that all-polymer formulation can improve device stability, however, PCE is not in satifsfaction, and the batch-to-batch variation leads to quality control issues. In this work, we constructed monodispersed tetramer NFA materials named G-1 and G-2, to best integrate the merits of small molecule and polymer. Density functional theory (DFT) calculations and experimental results showed that different connecting units at the centre could significantly affect the molecular planarity and thin film morphology. The alkene-bonded tetramer G-1 had a more regioregular structure, which leads to better molecular planarity, and more ordered packing in thin film. More importantly, the oligomeration induced a favourable face-on orientation, achieved a lower binding energy and exhibited a higher photoluminescence yield. As a result, the exciton and charge carrier kinetics was optimized with reduced non-radiative energy loss. The OSC based on PM6 : G-1 achieved a PCE of 19.6 %, which is the highest PCE reported so far for oligomer-based binary OSC. In addition, the device stability was largely improved, showing a lifetime over 10000 hours in the inverted OSC device.

Heteroatomic molecules for coordination engineering towards advanced Pb-free Sn-based perovskite photovoltaics.

As an ideal eco-friendly Pb-free optoelectronic material, Sn-based perovskites have made significant progress in the field of photovoltaics, and the highest power conversion efficiency (PCE) of Sn-based perovskite solar cells (PSCs) has been currently approaching 16%. In the course of development, various strategies have been proposed to improve the PCE and stability of Sn-based PSCs by solving the inherent problems of Sn2+, including high Lewis acidity and easy oxidation. Notably, the recent breakthrough comes from the development of heteroatomic coordination molecules to control the characteristics of Sn-based perovskites, which are considered to be vital for realizing efficient PSCs. In this review, the up-to-date advances in the design of heteroatomic molecules and their key functions in the fabrication of Sn-based perovskite films are comprehensively summarized. Firstly, the design principles of heteroatomic coordination molecules and their impact on the colloidal chemistry, crystallization dynamics, and defect properties of Sn-based perovskites are introduced. Then, state-of-the-art heteroatomic coordination molecules for efficient Sn-based PSCs are discussed in terms of their heteroatom types and functional groups. Lastly, we shed some light on the current challenges and future perspectives regarding the rational design of heteroatomic coordination molecules for further boosting the performance of Sn-based PSCs.

Fabrication of n-i-p perovskite solar cells based on strategy of buried interface modification

Normal (n-i-p) perovskite solar cells (PSCs) have received increasing attention due to their advantages such as high conversion efficiency and good stability. Tin dioxide is an ideal electron transport layer material for normal perovskite solar cells. Among various available electron transport layers, tin dioxide stands out because of its excellent stability, low density of defect states, and appropriate energy levels. The interface defects between tin dioxide and perovskite are the key factors restricting the improvement of the conversion efficiency in perovskite solar cells. Therefore, a method of fabricating normal perovskite solar cells based on the buried interface modification strategy is proposed in this work. By doping methylammonium bromide into tin dioxide to form a buried interface, the interface defects between tin dioxide and perovskite are reduced, the electron mobility of tin dioxide is enhanced, and the growth of high-quality perovskite materials is promoted. The conversion efficiency of the normal perovskite solar cells reaches 23.12%, providing an effective strategy for fabricating high-efficiency normal perovskite solar cells.

Application of advanced quantum dots in perovskite solar cells: synthesis, characterization, mechanism, and performance enhancement.

Quantum dots have garnered significant interest in perovskite solar cells (PSCs) due to their stable chemical properties, high carrier mobility, and unique features such as multiple exciton generation and excellent optoelectronic characteristics resulting from quantum confinement effects. This review explores quantum dot properties and their applications in photoelectronic devices, including their synthesis and deposition processes. This sets the stage for discussing their diverse roles in the carrier transport, absorber, and interfacial layers of PSCs. We thoroughly examine advances in defect passivation, energy band alignment, perovskite crystallinity, device stability, and broader light absorption. In particular, novel approaches to enhance the photoelectric conversion efficiency (PCE) of quantum dot-enhanced perovskite solar cells are highlighted. Lastly, based on a comprehensive overview, we provide a forward-looking outlook on advanced quantum dot fabrication and its impact on enhancing the photovoltaic performance of solar cells. This review offers insights into fundamental mechanisms that endorse quantum dots for improved PSC performance, paving the way for further development of quantum dot-integrated PSCs.

SnS-induced element diffusion Simultaneous optimization of interface and bulk defects in High-Efficiency CZTSSe solar cells

High-quality interfacial contact and absorber are significant for high-efficiency Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cells. With this in mind, the paper puts forward the idea of using a sputtering SnS interlayer at the CZTSSe/Mo interface. The high-temperature decomposition of SnS allowed for the compensation of S and Sn elements in the absorber, as well as induced the redistribution of Na and Cu elements. The diffusion of Na element to the absorber optimizes the crystal quality and improves the interface contact, and the Cu-poor absorber reduces the concentration of CuZn defects. Introducing the SnS-10 interlayer significantly reduces the charge loss, bulk and interface recombination of the device, leading to further improvements in the open-circuit voltage (VOC), short-circuit current density (JSC), and filling factor (FF). Finally, the power conversion efficiency (PCE) of CZTSSe thin film solar cells increased from 8.92 % to 10.49 %, in which the contribution rates of VOC, JSC, and FF to PCE were 27.12 %, 32.33 %, and 40.55 %, respectively. The most significant contribution of the electrical parameters to the PCE was the reverse saturation current density (J0). This finding provides an effective solution to obtain a high-quality interface and absorber, effectively restraining carrier recombination.

Subtly Modulating Bay Sites of Perylene Diimide Cathode Interface Layer for High‐Performance and High‐Stability Non‐Fullerene Organic Solar Cells

AbstractCathode interface layers (CILs) are crucial for optimizing the power conversion efficiency (PCE) and stability of organic solar cells (OSCs). Two small molecule CILs, PDINN‐TS and PDINN‐BS are developed, by modifying the bay sites of perylene diimide (PDI) with thieno [3,2‐b] thiophene and 2,2′‐bithiophene, separately. Due to better electron‐donating capacity and longer conjugate length of the 2,2′‐bithiophene, PDINN‐BS exhibits a stronger self‐doping effect and superior interface compatibility compared to PDINN‐TS. Consequently, in PM6: Y6 OSCs, PDINN‐BS achieved an elevated PCE of 16.95%, surpassing PDINN‐TS of 16.66%. Meanwhile, PDINN‐BS exhibits excellent universality. When employing PM6: BTP‐eC9 and PM6:L8‐BO systems, PDINN‐BS‐based device yielded PCE of 18.02% and 18.95%, outperforming PDINN‐TS of 17.51% and 18.38%, respectively. Furthermore, stability tests revealed that after being stored in the glovebox for 1500 h, PDINN‐BS retained 90% of its pristine PCE, compared to 86% for PDINN‐TS. PDINN‐BS showed longer 80% PCE decay (T80) of 150 h in air, 200 h at 70 °C heating in N2, and 500 h under 1 sun immersion, surpassing PDINN‐TS with 120, 130, and 380 h, respectively. This demonstrates that PDINN‐BS displayed superior stability under a complicated environment. Consequently, this study provides significative guidance for the exploitation of high‐performance and high‐stability OSCs.

Revealing the Effect of Solvent Additive Selectivity on Morphology and Formation Kinetics in Printed Non‐fullerene Organic Solar Cells at Ambient Conditions

AbstractSolvent additives enable the efficient modification of the morphology to improve the power conversion efficiency (PCE) of organic solar cells. However, the impact of solvent additive selectivity on the film morphology and formation kinetics is still unclarified. Herein, this work investigates two solvent additives, 1‐chloronaphthalene (1‐CN) and tetralin, characterized by their varying selectivity for the polymer donor (PBDB‐T‐2F) and the non‐fullerene small molecule acceptor (BTP‐C3‐4F). Specifically, 1‐CN exhibits superior solubility for BTP‐C3‐4F over PBDB‐T‐2F, whereas tetralin shows the opposite trend. The blend films with and without solvent additives are fabricated with the slot‐die coating at ambient conditions. Both solvent additives can promote larger phase separation and increase the size of crystals of the selectively dissolved component. In situ grazing‐incidence wide‐angle X‐ray scattering and UV–vis absorption spectra during printing unveil two distinct kinetic processes induced by 1‐CN and tetralin, leading to large‐sized crystals. 1‐CN can prolong the liquid‐solid phase separation to provide sufficient time for the BTP‐C3‐4F crystal growth but suppress the crystal growth of PBDB‐T‐2F. Tetralin can swell PBDB‐T‐2F and break down BTP‐C3‐4F crystals at the same time. Upon thermal annealing, the oversized crystals triggered by both solvent additives can be optimized to an appropriate size, resulting in an enhanced PCE.

Developing a Fluorinated Benzothiadiazole-Based Polymer Donor as Guest to Construct High-Performance Ternary Solar Cells.

Benzothiadiazole (BT) has shown promising applications in fullerene solar cells. However, few BT-based polymer donors exhibited a noticeable power conversion efficiency (PCE) for the fused-ring small molecular acceptor-based polymer solar cells (PSCs). Herein, we developed a D-A (D: donor, A: acceptor) polymer donor F-1 based on fluorinated BT (ffBT) as A unit and chlorinated benzo [1,2-b:4,5-b'] dithiophene (BDT-2Cl) as D unit. Thanks to the strong electron-withdrawing of ffBT unit, F-1 not only exhibited low-lying energy levels to increase open circuit voltage, but also existence noncovalent S···F to enhance molecular planarity and crystallinity. After incorporated F-1 as guest materials on PM6:L8-BO-based system to construct ternary device, the addition of F-1 can efficient promote the blend films exhibit excellent morphological compatibility, favorable phase separation, and molecular arrangement. As a result, the F-1 (5%):PM6:L8-BO-based device obtained an impressive PCE up to 19.47 %, which is much higher than the counterparts as PCE is 18.35% for PM6:L8-BO-based binary device. This study not only provided a practical and promising strategy to develop high-performance polymer donors by utilizing the advantages of noncovalent conformational locks, but also suggested an efficient strategy to further improve device performance by constructing ternary solar cells for BT unit-based PSCs.

Investigating Dopant Effects in ZnO as an Electron Transport Layer for Enhanced Efficiency in Organic Photovoltaics

AbstractThe power conversion efficiencies of organic solar cells greatly depend on the device architecture and choice of charge transporting materials. Improved power conversion efficiency (PCE) for inverted organic solar cells is observed when using Sn‐doped ZnO as the electron transporting layer. By doping the elements with different numbers of valence electrons (Al3+ and Sn4+ ions) into the ZnO matrix, device conversion efficiencies of 8.69% and 9.21%, respectively, are achieved. Conductive atomic force microscopy (CAFM) observations reveal that the Sn‐doped ZnO film exhibits better conductivity due to its larger number of carrier charges. X‐ray photoemission spectroscopy (XPS) indicates larger oxygen vacancies (OV) in Sn‐doped ZnO. Electrochemical characterization exhibits that there is a reduction in series resistance and charge transfer (CT) resistance for SZO, indicating the optimal charge transport capability of the electron transport layer (ETL). Ultrafast time‐resolved studies further show that, in comparison with Al‐doped ZnO and un‐doped ZnO, the elevated carrier concentration in Sn‐doped ZnO plays a significant role in augmenting the photocurrent. Thus, it is determined how dopants in ETL influence CT mechanisms, enhancing the photovoltaic conversion efficiency, thus contributing to the development of cost‐effective and efficient photovoltaic technologies.

Fusion Modes and Number of Fused Rings: Their Impact on Acceptor-Donor-Acceptor Nonfullerene Acceptors in Organic Solar Cells.

The power conversion efficiency (PCE) of organic solar cells (OSCs) devices has surpassed 19% owing to the blooming of fused-ring nonfullerene acceptors (NFAs), especially for acceptor-donor-acceptor (A-D-A) type NFAs. However, the structural effect of the angular/linear fusion mode and number of fused rings for A-D-A type NFAs on the photovoltaic performance in OSCs devices remains unclear. Herein, the A-D-A type NFAs (F-0Cl, IDIC8-H, and ITIC) have been selected to obtain the intrinsic role of structural design strategies including the angular/linear fusion mode and the number of fused rings. The results indicate that compared to the linear fusion mode in ITIC, the angular fusion mode in F-0Cl effectively diminishes electronic vibrational coupling within the low-frequency range, leading to lower charge reorganization during the exciton diffusion process. Meanwhile, it facilitates the generation of multiple charge transfer mechanisms at the donor/acceptor (D/A) interface and increases the rates of hole transfer. On the other hand, the decreased number of fused rings of NFAs could inhibit the exciton decay and charge recombination but increase the rates of exciton diffusion and exciton dissociation for individual NFAs and the rates of electron separation for D/A interface. This work provides theoretical insights into structural design strategies, such as linear/angular fusion, and the number of fused rings of NFA, which presents a promising outlook for further enhancing PCE of high-performance A-D-A type NFAs.

The Effect of Antisolvent Treatment on the Growth of 2D/3D Tin Perovskite Films for Solar Cells.

Antisolvent treatment is used in the fabrication of perovskite films to control grain growth during spin coating. We study widely incorporated aromatic hydrocarbons and aprotic ethers, discussing the origin of their performance differences in 2D/3D Sn perovskite (PEA0.2FA0.8SnI3) solar cells. Among the antisolvents that we screen, diisopropyl ether yields the highest power conversion efficiency in solar cells. We use a combination of optical and structural characterization techniques to reveal that this improved performance originates from a higher concentration of 2D phase, distributed evenly throughout the 2D/3D Sn perovskite film, leading to better crystallinity. This redistribution of the 2D phase, as a result of diisopropyl ether antisolvent treatment, has the combined effect of decreasing the Sn4+ defect density and background hole density, leading to devices with improved open-circuit voltage, short-circuit current, and power conversion efficiency.

Effect of titanium dioxide nanofillers on the properties of gel-polymer electrolytes and power conversion efficiency of dye-sensitized solar cells

Effect of titanium dioxide nanofillers on the properties of gel-polymer electrolytes and power conversion efficiency of dye-sensitized solar cells

Sulfur Vacancies Limit the Open-Circuit Voltage of Sb2S3 Solar Cells.

Antimony sulfide (Sb2S3) is a promising candidate as an absorber layer for single-junction solar cells and the top subcell in tandem solar cells. However, the power conversion efficiency of Sb2S3-based solar cells has remained stagnant over the past decade, largely due to trap-assisted nonradiative recombination. Here we assess the trap-limited conversion efficiency of Sb2S3 by investigating nonradiative carrier capture rates for intrinsic point defects using first-principles calculations and Sah-Shockley statistics. Our results show that sulfur vacancies act as effective recombination centers, limiting the maximum light-to-electricity efficiency of Sb2S3 to 16%. The equilibrium concentrations of sulfur vacancies remain relatively high, regardless of growth conditions, indicating the intrinsic limitations imposed by these vacancies on the performance of Sb2S3.

Solar Cells Manufactured Using Concentrated Solar Energy Toward Carbon Neutralization

AbstractThe high photoelectric conversion efficiency (PCE) of solar cells and their environmentally friendly, low‐carbon manufacturing processes are crucial for advancing carbon neutrality goals. This study introduces Fresnel lenses to focus sunlight for the sintering of mesoporous titanium dioxide (m‐TiO2) layers as an innovative method for fabricating perovskite solar cells (PSCs), effectively circumventing the energy‐intensive and carbon‐emitting high‐temperature furnace sintering traditionally required. Through this concentrated solar annealing technique, an efficient and eco‐friendly sintering of the m‐TiO2 layer is successfully achieved by removing organic residues from the precursor film and enhancing the film's transmittance, electrical conductivity, and grain size. Consequently, this has led to improved coverage of the perovskite layer and enhanced overall photovoltaic performance of the solar cells. Experimental results indicate that the m‐TiO2 film subjected to 60 min of concentrated sunlight sintering (CSS) demonstrates optimal photovoltaic performance, with the fabricated compact‐layer‐free PSCs achieving an impressive photoelectric conversion efficiency of up to 17.69%. This research not only offers a novel, cost‐effective approach for the sustainable production of PSCs but also contributes tangible solutions for the green transformation of the photovoltaic industry and the achievement of carbon neutrality. This work points the way toward using solar energy to prepare solar power generation devices.

Inverse design workflow discovers hole-transport materials tailored for perovskite solar cells.

The inverse design of tailored organic molecules for specific optoelectronic devices of high complexity holds an enormous potential but has not yet been realized. Current models rely on large data sets that generally do not exist for specialized research fields. We demonstrate a closed-loop workflow that combines high-throughput synthesis of organic semiconductors to create large datasets and Bayesian optimization to discover new hole-transporting materials with tailored properties for solar cell applications. The predictive models were based on molecular descriptors that allowed us to link the structure of these materials to their performance. A series of high-performance molecules were identified from minimal suggestions and achieved up to 26.2% (certified 25.9%) power conversion efficiency in perovskite solar cells.