Tandem Organic Solar Cells Research Articles

High efficiency homojunction tandem organic solar cells with all solution processable interconnect layer

In the field of organic photovoltaics, the power conversion efficiency of single junction solar cells continues to improve. However, tandem organic solar cells are poised to push the efficiency limits even further and offer a promising avenue for improving the performance of organic photovoltaic devices. This study reports the development of an all-solution processed interconnecting layer (ICL) based on ZnO NPs:PEI/PEI/PEDOT:PSS/2PACz for tandem solar cells. The PM6:BTP-eC9 active layer material was adjusted for its donor-to-acceptor (D/A) ratio and film thickness as the front and back sub-cells. The ICL exhibits favorable mechanical, electrical and optical properties. Through multidimensional modulation, the front and rear sub-cells have been optimized to obtain highly efficient homojunction tandem solar cells. The tandem solar cell has a structure of indium tin oxide (ITO)/PEDOT:PSS/2PACz/active layer/ICL/active layer/PNDIT-F3N/Ag. This optimization resulted in a power conversion efficiency (PCE) of 19.9 %, which is the highest reported efficiency for homojunction tandem organic solar cells to date. Our research demonstrates that the PCE of homojunction tandem cells can be significantly improved by careful design of the interconnecting layers and optimization of the donor-to-acceptor (D/A) ratio. This strategy may provide guidance for further improvements in homojunction tandem cells.

Photosystem I enhanced perovskite–Organic tandem solar cell efficiency

Tandem solar cells (TSC) have been introduced to better absorb the spectrum of sunlight and reduce optical loss. Among these, perovskite–organic tandem solar cells (P-OTSC) have emerged as a prominent topic over the last decade due to their complementary absorption spectrum. Additionally, incorporating diverse pigmented protein complexes in TSC fabrication is becoming more common. Natural chlorophyll-containing photosystems have garnered significant attention for their naturally solar-tuned absorption spectra. Photosystem I protein (PSI), is the most robust component of oxygenic photosynthesis and contains over 100 Chl a molecules/complex with two sharp absorbance peaks at 430 and 665 nm. PSI offers a second and complementary active layer because P-OTSCs often have a low extinction coefficient in the red wavelength region. In this research, the performance of P-OTSCs was enhanced by improving the absorption spectrum by utilizing an isolated plant PSI complex. The circuit current density (Jsc) increased from 14.23 mA/cm² to 14.95 mA/cm², and the power conversion efficiency (PCE) of P-OTSCs increased from 19.32 % to 20.24 %. We also observed that the external quantum efficiency (EQE) shows an apparent increase in the long wavelength region, reflecting the absorbance of light by PSI. This work is the first to report the integration of PSI into perovskite–organic tandem solar cells, and it motivates new design considerations that can further boost efficiency and utilize natural, earth-abundant pigment proteins.

A Pyrazinyl Wide‐Bandgap Polymer Donor Yields 19.35% Efficiency in Tandem Organic Solar Cells

A Pyrazinyl Wide‐Bandgap Polymer Donor Yields 19.35% Efficiency in Tandem Organic Solar Cells

Molecular Design and Organic Photovoltaic Applications of Carboxylate‐Functionalized P‐type Polymers

AbstractThe significant progress of p‐type and n‐type active layer materials in the past several years has pushed the power conversion efficiency (PCE) of organic solar cells (OSCs) toward 19%. Due to the relatively low synthesis cost and simple synthesis method of carboxylate‐containing building blocks, including thiophene, thieno[3,2‐b]thiophene, thieno[3,4‐b]thiophene, furan, pyrazine, benzodithiophene, benzothiazole, quinoxaline, etc., are widely used to construct p‐type photovoltaic polymers. These resulting carboxylate‐bearing polymers present downward energy levels, high absorption coefficient, narrow bandgap, high hole mobility, and strong aggregation behavior, which have dabbled in the fabrication of mechanically stretchable, semitransparent, indoor, and tandem OSCs, etc., and produce excellent photovoltaic performance. The low‐cost carboxylate‐containing copolymers exhibit a satisfying PCE approaching 17%, and the random terpolymer systems achieve a high PCE over 19%. This review focuses on the progress of carboxylate‐containing photovoltaic polymers, summarizes the molecular characteristics, discusses their structure‐performance relationship, and offers a summary and outlook on the challenges for future molecular development.

Utilizing Metal Oxide Thin Films for Device Engineering of Solution-Processed Organic Multi-Junction Solar Cells

Electron and hole transporting layers play a major role in high-performance and stable organic-based optoelectronic devices. This paper demonstrates detailed device engineering of multi-junction organic photovoltaics built on two different metal oxide-based electron and hole transport (buffer) layers prepared by thermal or solution-processed methods. The main focus is on the device processing parameters as well as practical details of preparation of buffer layers to give the research community a clear, step-by-step recipe to successfully replicate and build series and parallel connected multi-junction solution-based organic solar cells for their needs. Here, the recipes and deposition conditions of two metal oxide buffer layers are presented in detail, based on basic commercially available materials and tools, to achieve well-engineered tandem (multi-junction) solution-processed organic solar cells. The buffer layers have appropriate energy levels for electrical selectivity of anode and cathode electrodes, and they are highly stable and chemically compatible with processing of solution-based polymer solar cells. To demonstrate the engineering steps of multi-junction devices, the PCE10:PC70BM blend is used as the active layer for all subcells. Then, to improve the power conversion efficiency of the single-junction photovoltaic device, PCE10:PC70BM blend is used in combination with DPPx:PC70BM with different absorption spectra for bottom and top subcell active layers. An optimized series tandem device with 10.6% power conversion efficiency is demonstrated. Generally, the device structures reported here can also be used for other types of optoelectronic devices, such as light emitting diodes and photodetectors.

Pyrrole-Based Fully Non-fused Acceptor for Efficient and Stable Organic Solar Cells.

Organic solar cells (OSCs) are still suffering from the low light utilization and unstable under ultraviolet irradiation. To tackle these challenges, we design and synthesize a non-fused acceptor based on 1-(2-butyloctyl)-1H-pyrrole as π-bridge unit, denoted as GS70, which serves as active layer in the front-cell for constructing tandem OSCs with a parallel configuration. Benefiting from the well-complementary absorption spectra with the rear-cell, GS70-based parallel tandem OSCs exhibit an improved photoelectron response over the range between 600-700 nm, yielding a high short-circuit current density of 28.4 mA cm-2. The improvement in light utilization translates to a power conversion efficiency of 19.4 %, the highest value among all parallel tandem OSCs. Notably, owing to the intrinsic stability of GS70, the manufactured parallel tandem OSCs retain 84.9 % of their initial PCE after continuous illumination for 1000 hours. Overall, this work offers novel insight into the molecular design of low-cost and stability non-fused acceptors, emphasizing the importance of adopting a parallel tandem configuration for achieving efficient light harvesting and improved photostability in OSCs.

Regulating the crystallization of mixed-halide perovskites by cation alloying for perovskite–organic tandem solar cells

Inhomogeneous halide distribution and high defect levels result from unbalanced crystallization in mixed halide perovskites. IA cations regulate crystallization and minimize defects, creating high-performance perovskite solar cells and tandems.

Phase Segregation and Voltage Loss Mitigated Highly Efficient Perovskite–Organic Tandem Solar Cells with a Simple Ambipolar SnOx Interconnecting Layer (Adv. Funct. Mater. 52/2023)

Phase Segregation and Voltage Loss Mitigated Highly Efficient Perovskite–Organic Tandem Solar Cells with a Simple Ambipolar SnO<i>_x</i> Interconnecting Layer (Adv. Funct. Mater. 52/2023)

Manipulating Nanowires in Interconnecting Layer for Efficient Tandem Organic Photovoltaics†

Comprehensive SummaryOwing to the function of manipulating light absorption distribution, tandem organic solar cells containing multiple sub‐cells exhibit high power conversion efficiencies. However, there is a substantial challenge in precisely controlling the inter‐subcells carrier migration which determines the balance of charge transport across the entire device. The conductivity of “nanowires”‐like conducting channel in interconnecting layer between sub‐cells should be improved which calls for fine engineering on the morphology of polyelectrolyte in interconnecting layer. Here, we develop a simple method to effectively manipulating the domains of conductive components in commercially available polyelectrolyte PEDOT:PSS. The use of poor solvent could effectively modify the configuration of polystyrene sulfonic acid and thus the space for conductive components. Based on our strategy, the insulated shells wrapping conductive domains are thinned and the efficiencies of tandem organic solar cells are improved. We believe our method might provide guidance for the manufacture of tandem organic solar cells.

An Efficient Solution‐Processed Interconnecting Layer for Large‐Area Tandem Organic Solar Cells

Interconnecting layer (ICL) is a key part of the tandem organic solar cells (OSCs) to achieve high efficiency. The ICLs of efficient inverted nonfullerene OSCs are complicated that comprise vacuum‐deposited MoO3, solution‐processed ZnO, and an additional thin silver (or PEDOT:PSS) film in between. Herein, an efficient fully solution‐processed ICL is first reported that comprises a PEDOT:F layer and a ZnO layer. The PEDOT:F is short for poly(3,4‐ethylenedioxythiophene):perfluorinated sulfonic acid ionomer that is alcohol dispersed and has a work function of 5.6 eV for hole collection. The ZnO is used for electron collection. The PEDOT:F/ZnO has a conductivity of 2.28 × 10−3 S cm−1 which can play a recombination zone. The solution‐processed ICL of PEDOT:F/ZnO has been validated in both two‐junction and triple‐junction solar cells. The tandem cells show high fill factor (FF) of 76–80% and high open‐circuit voltage (VOC) which is nearly the sum of the single‐junction OSCs. The PEDOT:F/ZnO ICL has also been used to fabricate large‐area tandem organic module (15.48 cm2) that shows a VOC of 10.25 V, FF of 75.1%, and a power conversion efficiency of 13.24%. The PEDOT:F/ZnO is a promising ICL for high‐performance tandem OSCs.

Phase Segregation and Voltage Loss Mitigated Highly Efficient Perovskite–Organic Tandem Solar Cells with a Simple Ambipolar SnOx Interconnecting Layer

AbstractThe wide‐bandgap (WBG) perovskite solar cells (PSCs) and narrow‐bandgap organic solar cells (OSCs) integrated tandem solar cells (TSCs) show great potential for overwhelming single junction structure, especially the advantage of applying orthogonal solvents for allowing solution processed of each subcell. However, the WBG perovskite with high Br content suffers from serious phase segregation and voltage loss. The commonly used interconnection layer (ICL) in TSCs requires a vacuum‐deposited thin metal recombination layer leading to remarkable optical loss. Herein, WBG perovskite with a bandgap of 1.77 eV yields an impressive open‐circuit voltage (VOC) of 1.33 V and a minimum voltage loss of 0.44 V by an elaborate dielectric interface structure reducing the interfacial recombination. Furthermore, the WBG perovskite with a simple SnOX buffer layer exhibits significantly suppressed phase segregation and improved performance. Consequently, a simplified buffer layer based on the SnOX that serves as the ICL in perovskite–organic TSCs contributing enhanced light harvesting in the near‐infrared region is developed, yielding an efficiency of 22.31%. The simplified ICL that does not involve a metal layer is a potential strategy for scalable and flexible perovskite‐based TSCs.

Inverted organic tandem solar cells with a charge recombination stack employing spatially confined p-type electrical doping

We report on the application of solution-based p-type electrical doping using 12-molybdophosphoric acid hydrate (PMA) to the fabrication of organic tandem solar cells. Such a doping approach leads to a spatially confined vertical doping profile down to a limited depth from the surface of polymer films, thus allowing the hole-collecting component of the charge recombination stack to be embedded in the photoactive layer of the bottom sub-cell. This simplifies the device architecture by removing the need for an extra dedicated hole-collecting layer. It is shown that this novel charge recombination stack comprising a PMA-doped bottom photoactive layer and a trilayer of Ag/AZO/PEIE is compatible with a solution-processed top photoactive layer. The fabricated inverted organic tandem solar cells exhibit an open-circuit voltage that is close to the sum of the open-circuit voltages of the individual sub-cells, and a fill factor that is close to the better fill factor of the two sub-cells.

Tandem organic solar cells with 20.6% efficiency enabled by reduced voltage losses.

Large voltage losses are the main obstacle for achieving high efficiency in organic solar cells (OSCs). Here we construct ternary OSCs by introducing an asymmetric small molecule acceptor AITC into PBDB-TCl : BTP-eC9 system and demonstrate the effectiveness in simultaneously decreasing energy disorder and non-radiative voltage losses. It is found that the introduction of AITC can modify domain size and increase the degree of crystallinity, which enhances open-circuit voltage and power conversion efficiency (19.1%, certified as 18.9%). Inspiringly, an output efficiency of 20.6% of the constructed tandem OSCs based on PBDB-TCl : AITC : BTP-eC9 ternary active layer output a recorded efficiency of 20.6% (certified as 20.3%), which is the highest value in OSCs field to date. This work demonstrates that decreasing the voltage losses by ternary strategy and constructing of tandem architecture are effective approaches towards improving photovoltaic performance.

Screening Efficient Tandem Organic Solar Cells with Machine Learning and Genetic Algorithms

Screening Efficient Tandem Organic Solar Cells with Machine Learning and Genetic Algorithms

Tandem organic solar cells with a large VOC by control of the active-layer concentration

Tandem organic solar cells with a large VOC by control of the active-layer concentration

Near-infrared absorbing acceptor with suppressed triplet exciton generation enabling high performance tandem organic solar cells

Reducing the energy loss of sub-cells is critical for high performance tandem organic solar cells, while it is limited by the severe non-radiative voltage loss via the formation of non-emissive triplet excitons. Herein, we develop an ultra-narrow bandgap acceptor BTPSeV-4F through replacement of terminal thiophene by selenophene in the central fused ring of BTPSV-4F, for constructing efficient tandem organic solar cells. The selenophene substitution further decrease the optical bandgap of BTPSV-4F to 1.17 eV and suppress the formation of triplet exciton in the BTPSV-4F-based devices. The organic solar cells with BTPSeV-4F as acceptor demonstrate a higher power conversion efficiency of 14.2% with a record high short-circuit current density of 30.1 mA cm−2 and low energy loss of 0.55 eV benefitted from the low non-radiative energy loss due to the suppression of triplet exciton formation. We also develop a high-performance medium bandgap acceptor O1-Br for front cells. By integrating the PM6:O1-Br based front cells with the PTB7-Th:BTPSeV-4F based rear cells, the tandem organic solar cell demonstrates a power conversion efficiency of 19%. The results indicate that the suppression of triplet excitons formation in the near-infrared-absorbing acceptor by molecular design is an effective way to improve the photovoltaic performance of the tandem organic solar cells.

Perovskite organic tandem solar cell: A design towards improved efficiency

Perovskite organic tandem solar cell: A design towards improved efficiency

Sequential Deposition of Multicomponent Bulk Heterojunctions Increases Efficiency of Organic Solar Cells.

Constructing tandem and multi-blend organic solar cells (OSCs) isan effective way to overcome the absorption limitations of conventional single-junction devices. However, these methods inevitably require tedious multilayer deposition or complicated morphology-optimization procedures. Herein, sequential deposition is utilized as an effective and simple method to fabricate multicomponent OSCs with a double-bulk heterojunction (BHJ) structure of the active layer to further improve photovoltaic performance. Two efficient donor-acceptor pairs, D18-Cl:BTP-eC9 and PM6:L8-BO, are sequentially deposited to form the D18-Cl:BTP-eC9/PM6:L8-BO double-BHJ active layer. In these double-BHJ OSCs, light absorption is significantly improved, and optimal morphology is also retained without requiring a more complicated morphology optimization involved in quaternary blends. Compared to the quaternary blend devices, energy loss (Eloss ) is also reduced by rationally matching each donor with an appropriate acceptor. Consequently, the power conversion efficiency (PCE) is improved from 18.25% for D18-Cl:BTP-eC9 and 18.69% for PM6:L8-BO based binary blend OSCs to 19.61% for the double-BHJ OSCs. In contrast, a D18-Cl:PM6:L8-BO:BTP-eC9 quaternary blend of OSCs exhibited a dramatically reduced PCE of 15.83%. These results demonstrate that a double-BHJ strategy, with a relatively simple processing procedure, can potentially enhance the device performance of OSCs and lead to more widespread use.

Tandem organic solar cells with efficiency over 19% via the careful subcell design and optimization

Tandem organic solar cells with efficiency over 19% via the careful subcell design and optimization

Towards large area production: stretchability, flexibility, and stability of efficient printed organic tandem solar cells

Scaling up organic tandem solar cells from laboratory to large-scale production.