Achieving over 16% efficiency for single-junction organic solar cells

inorganic photovoltaic cells based on crystal-silicon, the solution processability of OPV cells makes it suitable for the largescale solution production at room temperature via the roll-to-roll method, which promises low-cost and large area device fabrication onto flexible substrates. [4][5][6] Benefiting from the great efforts devoted to the design of new materials, [7][8][9][10][11][12][13] optimization of the blend morphology, [14][15][16][17][18] understanding the charge generation mechanism, [19][20][21][22][23][24][25][26] significant progress has been achieved in the last few years. Recently, the power conversion efficiencies (PCEs) of OPV cells have surpassed ≈15%. [27][28][29] However, the devices with cutting-edge performance are fabricated using highly toxic solvents like chlorinated and/or aromatic solvents, which is not adaptable for large-scale production and becoming a severe problem that hinders the mass production of the OPV cells. Therefore, the material design of OPV materials should take both the efficiency and processability into consideration.At present, the commonly used processing solvents for high-performance OPV materials are chlorobenzene (CB) and chloroform (CF), as they possess excellent dissolving capability of the highly conjugated structures. [30][31][32] Over the last few years, the design and application of nonfullerene acceptors (NFAs) have achieved Recent advances in nonfullerene acceptors (NFAs) have enabled the rapid increase in power conversion efficiencies (PCEs) of organic photovoltaic (OPV) cells. However, this progress is achieved using highly toxic solvents, which are not suitable for the scalable large-area processing method, becoming one of the biggest factors hindering the mass production and commercial applications of OPVs. Therefore, it is of great importance to get good eco-compatible processability when designing efficient OPV materials. Here, to achieve high efficiency and good processability of the NFAs in eco-compatible solvents, the flexible alkyl chains of the highly efficient NFA BTP-4F-8 (also known as Y6) are modified and BTP-4F-12 is synthesized. Combining with the polymer donor PBDB-TF, BTP-4F-12 shows the best PCE of 16.4%. Importantly, when the polymer donor PBDB-TF is replaced by T1 with better solubility, various eco-compatible solvents can be applied to fabricate OPV cells. Finally, over 14% efficiency is obtained with tetrahydrofuran (THF) as the processing solvent for 1.07 cm 2 OPV cells by the blade-coating method. These results indicate that the simple modification of the side chain can be used to tune the processability of active layer materials and thus make it more applicable for the mass production with environmentally benign solvents. Organic PhotovoltaicsOrganic photovoltaic (OPV) cells consisting of organic layers as photoactive materials are one of the most promising next-generation photovoltaic technologies to harvest clean and renewable solar energy. [1][2][3] When compared with the conventional

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Eco‐Compatible Solvent‐Processed Organic Photovoltaic Cells with Over 16% Efficiency

et al. 2019

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“…[7,8] Be that as it may, difficulties in tuning the molecular structure and electronic properties, as well as the comparatively high cost of production of fullerene-based acceptors are drawbacks that have triggered the search for nonfullerene acceptors (NFAs) as an alternative. [17,18] In tandem and ternary systems, PCEs reaching even up to 17.3% have been recently achieved. [17,18] In tandem and ternary systems, PCEs reaching even up to 17.3% have been recently achieved.…”

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Quantifying the Nongeminate Recombination Dynamics in Nonfullerene Bulk Heterojunction Organic Solar Cells

Vollbrecht

Брус

et al. 2019

Advanced Energy Materials

140

147

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the continued research has led to power conversion efficiencies (PCEs) over 11% for single-junction devices. [7,8] Be that as it may, difficulties in tuning the molecular structure and electronic properties, as well as the comparatively high cost of production of fullerene-based acceptors are drawbacks that have triggered the search for nonfullerene acceptors (NFAs) as an alternative. [9][10][11][12][13][14][15][16] Noteworthy improvements have been made over the last few years, and state-of-the-art NFA-OSCs have been reported with PCEs over 16 %, thus outperforming their fullerene-based counterparts. [17,18] In tandem and ternary systems, PCEs reaching even up to 17.3% have been recently achieved. [19,20] Additionally, the reduction in the bandgap of NFAs opens up the possibility to fabricate semitransparent OSCs that could be applied in building-integrated photovoltaics or power generating greenhouses. [21][22][23][24] To further improve the performance of OSCs, loss-processes such as nongeminate recombination, the recombination of electrons and holes which do not originate from the same exciton, have to be curtailed. This includes bimolecular recombination (also known as Langevin recombination), where charge carriers recombine directly from band to band, as well as trap-assisted recombination (also known as Shockley-Read-Hall recombination), where states deep in the bandgap act as efficient recombination centers. A detailed understanding of these mechanisms responsible for the aforementioned recombination losses is required. [25] Whether or not there are considerable differences in recombination dynamics between NFA-OSCs and fullerene-based OSCs, has yet to be understood since most research in regard to recombination dynamics was performed only with OSCs employing fullerene acceptors. [26][27][28] Furthermore, the majority of studies describe recombination dynamics based on a numerical, drift-diffusion model under the assumption of an effective-medium for the BHJ active layer. [29][30][31][32][33][34][35][36][37][38] The concentration of charge carriers is the key differential parameter in the theory of recombination dynamics. However, only integral parameters (electrical conductivity, impedance, open-circuit voltage, V OC ) can be directly measured by experiments. Therefore, the primary challenge of the theoretical background of any method developed to quantify recombination processes in photovoltaic devices is based on finding the appropriate relationship between the measured In this study, a comprehensive analytical model to quantify the total nongeminate recombination losses, originating from bimolecular as well as bulk and surface trap-assisted recombination mechanisms in nonfullerene-based bulk heterojunction organic solar cells is developed. This proposed model is successfully employed to obtain the different contributions to the recombination current of the investigated solar cells under different illumination intensities. Additionally, the model quantitatively describes the experimentally measured ope...

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“…[33,34] It was reflected in the decline of fill factor (FF) with the increase of film thickness. [1][2][3][4] Recently, due to the rapid innovation of nonfullerene acceptors (NFAs), [5][6][7][8][9][10][11][12][13][14][15] a great number of single-junction organic solar cells with power conversion efficiencies (PCEs) over 15% [16][17][18][19][20][21] have [35,36] Thus, it is still a challenge to obtain high efficiency devices with active layer thickness tolerance.…”

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confidence: 99%

High Performance Thick‐Film Nonfullerene Organic Solar Cells with Efficiency over 10% and Active Layer Thickness of 600 nm

Zhang

Feng

Meng

et al. 2019

Advanced Energy Materials

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been reported. And for tandem solar cells, the PCE has reached 17%. [22] However, the vast majority of those device performances were obtained with layer-thicknesses at around 100 nm [23][24][25][26][27][28][29] and decreased drastically with the increase of the active layer thickness, which limits their application in the roll to roll large-scale solution printing technology. [30,31] Furthermore, 20%-40% of the incident photon flux were wasted in such a active layer thickness, [32] which directly limits the short circuit current density (J sc ) of the corresponding OSCs. Thus, it is necessary to develop high efficiency OSCs with tolerance of the active layer thickness. However, a lot of research work have proved that the charge collection efficiency of a device is inversely proportional to the square of the film thickness of the active layer. [33,34] It was reflected in the decline of fill factor (FF) with the increase of film thickness. Also, the J sc will decrease due to the severe bimolecular recombination. [35,36] Thus, it is still a challenge to obtain high efficiency devices with active layer thickness tolerance. To date, in the reported cases with active layer thickness tolerance, most are based on fullerene derivative acceptors and it has been found that the donor materials with high crystallinity and balanced mobility with fullerene derivative acceptors manifested better performance with high film thickness. [35][36][37][38] Compared with fullerene derivatives based OSCs, it is much more challenging to realize thick-film NFAs OSCs with high performance since the electron mobilities of NFAs are usually lower than that of fullerene derivative acceptors. [39,40] Thus, the charge transport and collection process in those NFA based thick films are not efficient. So far, great attentions have been drawn on the NFA based thick film OSCs and much progress have been made. For examples, Yip and co-workers reported devices based on PffBT4T-2OD:EH-IDTBR and realized a PCE of 9.1% with an active layer thickness of 300 nm by optimizing device architectures to overcome the space-charge effects. [41] Zhang and co-workers reported devices based on PM6:IDIC with PCEs of 11.9% under the film thickness of 150 nm and 11.3% under the condition of 255 nm condition. Although the device performance is good enough, the cases with thicker active layers Developing efficient organic solar cells (OSCs) with relatively thick active layer compatible with the roll to roll large area printing process is an inevitable requirement for the commercialization of this field. However, typical laboratory OSCs generally exhibit active layers with optimized thickness around 100 nm and very low thickness tolerance, which cannot be suitable for roll to roll process. In this work, high performance of thick-film organic solar cells employing a nonfullerene acceptor F-2Cl and a polymer donor PM6 is demonstrated. High power conversion efficiencies (PCEs) of 13.80% in the inverted structure device and 12.83% in the conventional structure device are achi...

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Achieving over 16% efficiency for single-junction organic solar cells

Cited by 850 publications

References 40 publications

Eco‐Compatible Solvent‐Processed Organic Photovoltaic Cells with Over 16% Efficiency

Eco‐Compatible Solvent‐Processed Organic Photovoltaic Cells with Over 16% Efficiency

Quantifying the Nongeminate Recombination Dynamics in Nonfullerene Bulk Heterojunction Organic Solar Cells

High Performance Thick‐Film Nonfullerene Organic Solar Cells with Efficiency over 10% and Active Layer Thickness of 600 nm

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