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Organic ternary solar cells as a more simple, more powerful, more stability photovoltaic technology has been attracting more and more attention, and recently the power conversion efficiency has exceeded 18%. In order to promote the commercialization of organic photovoltaics, work mechanisms and the improvement origin should be researched more deeply. In addition, eco-compatible solvents and large-scale fabricating methods should be adopted along with the improvement of efficiency and stability. [Display omitted] • The mechanisms of organic ternary solar cells are discussed. • Various roles of the third component in the active layer are discussed. • The challenges and perspective of organic ternary solar cells are discussed. The record of power conversion efficiency (PCE) of organic solar cells (OSCs) is updating every day, and the value has exceeded 19% already, but it still lags behind those of commercialized inorganic solar cells. The addition of a third component not only can reduce energy loss for achieving a higher open circuit voltage (V OC), but also can enlarge the light harvesting range as well as optimize morphology for getting a higher short circuit current (J SC) and fill factor (FF). For further promoting the development of organic photovoltaic technology, this article first presents general principles of organic ternary solar cells (OTSCs), and then summarizes the recent developments of OTSCs in terms of the roles of third component. In the end, the challenges and perspectives for OTSCs are discussed. This review may provide guidance for preparing highly efficient organic ternary solar cells. [ABSTRACT FROM AUTHOR]

A novel small-molecule (SM) acceptor DTF-IC is designed and synthesized in this work. The power conversion efficiency (PCE) of ternary OSCs increased up to 12.14% from 10.90% by incorporating 10 wt% of DTF-IC as second acceptors into the binary OSCs consisting of PBDB-T as donor and IT-M as acceptor. This was mainly due to the large increase in short-circuit current (J sc) from 16.18 to 17.95 mA/cm2, without any drop in the open-circuit voltage (V oc) and fill factor (FF). The addition of DTF-IC enabled the donor and acceptor to form a distinct complementary absorption profile in the visible-light region, which boosted the photon harvesting in the range of 730–800 nm and consequently increased the J sc of the ternary system by 11%. Moreover, there was an energy transfer between the two SM acceptors, favorable for enhancing charge separation and transfer as well as reducing charge recombination at PBDB-T:IT-M and PBDB-T:DTF-IC interface. Simultaneously, HOMO and LUMO energy levels of DTF-IC were lower than those of PBDB-T, but still higher than those of IT-M. Thus, DTF-IC is able to provide a cascading energy level with the host donor and acceptor which are beneficial for efficient charge transfer between the acceptors and facilitating exciton dissociation and carrier transport. Meanwhile, the highly crystalline DTF-IC as a third component can improve the crystallization process of the active layer while maintaining proper phase separation. This work proposes a novel idea for non-fullerene acceptors achieved via twin spiro-type structure modifying by indanone and provides a new direction for the selection of ternary solar cell materials. [ABSTRACT FROM AUTHOR]

An optimal PCE of 17.81% is achieved in LbL type OPVs by employing solvent additives for the layered optimization, which should be among the top level for all the LbL type binary OPVs. The performance improvement should be benefited from simultaneously improved J SC and FF due to the individually optimized photon harvesting and molecular arrangement, as well as suppressed charge recombination. [Display omitted] • A PCE of 17.81% is achieved in the optimal LBL type OPVs. • The additives can act as photon harvesting reinforcer and morphology regulator. • The increased crystallize with additive can facilitate more swell matrix for exciton diffusion. In this work, layer-by-layer (LbL) type OPVs are constructed with wide bandgap polymer PNTB6-Cl as donor and nonfullerene material BTP-4F-12 as acceptor. The layered optimization strategy is employed via separately incorporating the diphenyl ether (DPE) and 1,8-diiodooctane (DIO) into PNTB6-Cl chlorobenzene solution and BTP-4F-12 chloroform solution. A power conversion efficiency (PCE) of 17.81% was achieved from the optimal LbL type OPVs with two solvent additives, which should be among the top level for LBL type binary OPVs. The incorporation of DPE and DIO can separately induce more ordered PNTB6-Cl and BTP-4F-12 orientation, which should contribute to charge transport with suppressed charge recombination in active layers. Meanwhile, BTP-4F-12 crystallization is strongly increased with the incorporation of DIO, which should facilitate more swell matrix for exciton diffusion in active layers. Over 13% PCE improvement can be realized in LbL type OPVs by incorporating two additives, benefiting from simultaneously improved short circuit current density (J SC) of 26.89 mA cm−2 and fill factor (FF) of 75.79%. Meanwhile, the PCE of optimized LbL type OPVs is higher than that of 17.33% for the optimized OPVs with bulk-heterojunction (BHJ) configuration, which reveals that layered optimization strategy should be a promising approach to achieve highly efficient LbL type OPVs. [ABSTRACT FROM AUTHOR]

Abstract: Herein we present a methodology for improving the power conversion efficiency of organic solar cells made by photoactive layers of poly(3-hexylthiophene) (P3HT) and phenyl-C61 butyric acid methyl ester (PCBM) of non-optimized microstructure. In our study we achieve a 47% improvement in the power conversion efficiency (PCE) of the device by utilizing a thiophene-based quinoid (QBT) moiety as the third component in the P3HT:PCBM:QBT photoactive layers. Based on a set of independent characterization experiments we address the QBT composition dependent photophysical, electrical, thermal, structural and morphology-related properties of the ternary photovoltaic P3HT:PCBM:QBT system for elucidating the origin of the PCE improvement. In small amounts (0.3–0.6wt%), QBT serves as a nucleation agent, it enlarges the size of the P3HT crystallites by 15% and it increases the fraction of well-ordered P3HT chains in the P3HT:PCBM:QBT layer. The improved microstructure of the photoactive layer in combination with the QBT-assisted photo-induced hole transfer step from PCBM to P3HT, lead to an increase of the charge photogeneration yield in the P3HT:PCBM:QBT triple bulk heterojunction. The relatively small optical gap of QBT facilitates a resonant energy transfer step from the photoexcited PCBM to the QBT followed by a charge transfer process between QBT and the P3HT matrix. Based on these findings we propose general guidelines for the design of next generation functional additives to be used in organic photovoltaics. [Copyright &y& Elsevier]

Abstract: Two series of P3HT-based polymer solar cell (PSCs) only with different electron acceptors PC70BM or PC60BM were investigated under the same conditions. The PSCs with PC70BM as the electron acceptor exhibit a relatively strong and broad absorption in the visible range and high external quantum efficiency, which results in a relatively high open circuit voltage (V oc ) of 0.62V, short circuit current density (J sc ) of 11.85mA/cm2 and power conversion efficiency (PCE) of 3.52%. The PSCs with PC60BM as the electron acceptor have a relatively low V oc of 0.58V, J sc of 10.68mA/cm2 and PCE of 3.02% due to the weak absorption of PC60BM in the visible light range. The function of PC70BM instead of PC60BM as electron acceptor could be summarized as follows: i) the strong absorption PC70BM in the visible range results in much more photon harvesting; ii) the relatively low electron mobility and relatively big size of PC70BM molecule influences the charge transporting and phase separation. The ultimate performances of PSCs are codetermined by the photon harvesting, exciton dissociation, charge carrier transport and collection. [Copyright &y& Elsevier]

Abstract: Organic semiconductors usually show high absorption coefficients only over a limited spectral range. This has to be taken into account when designing organic solar cells with low-energy gap absorbers, as it is likely that these cells will have reduced harvesting abilities for photons of higher energy. We will present two routes to tackle this problem via luminescence and energy transfer and outline three novel concepts of how to integrate these mechanisms. We use an efficient low-energy gap organic solar cell based on zinc-phthalocyanine and fullerene C60 as a model system. [Copyright &y& Elsevier]

Ternary strategy has been confirmed as an efficient method to improve the power conversion efficiency (PCE) of organic photovoltaics (OPVs). The 15.7% PCE is achieved from PM6:Y6 based binary OPVs. One nonfullerene acceptor Br-ITIC and fullerene derivative PC 71 BM are selected as the third component on the basis of efficient binary OPVs, respectively. The optimized ternary OPVs exhibit 16.4% and 16.2% PCE with Br-ITIC and PC 71 BM as the third component, respectively, corresponding to the short circuit current density (J SC) of 25.5 mA cm−2 vs. 25.6 mA cm−2, open circuit voltage (V OC) of 0.854 V vs. 0.836 V and fill factor (FF) of 75.1% vs. 75.6%. The advantage on photovoltaic parameters of two ternary OPVs may be recombined into one cell by employing PC 71 BM as the fourth component. A 16.8% PCE is achieved from the optimized quaternary OPVs, resulting from the further increased J SC of 25.8 mA cm−2 and FF of 76.4% compared with the optimized ternary OPVs. The third party certificated PCE of quaternary OPVs is 16.2%. In comparison to 15.7% PCE of the binary OPVs, about 4.5% and 7.0% PCE improvement are step-by-step achieved from the optimized ternary and quaternary OPVs, respectively. Multi-components strategy may provide enough room to achieve highly efficient OPVs. Based on highly efficient binary OPVs, Br-ITIC and PC 71 BM were successively incorporated into the active layer as the third and the fourth component, leading to the step-by-step PCE improvement from 15.7% to 16.4% and then to 16.8%. Image 1 • A PCE of 16.8% is achieved in the optimized quaternary OPVs. • Photogenerated exciton distribution can be optimized by employing multi-components strategy. • PC 71 BM can act as a morphology regulator to optimize molecular arrangement and phase separation. [ABSTRACT FROM AUTHOR]