From fullerene acceptors to non-fullerene acceptors: prospects and challenges in the stability of organic solar cells (original) (raw)
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Designation and Match of Non-Fullerene Acceptors with X-Shaped Donors toward Organic Solar Cells
In this work, a series of PDI derivatives by substituting different aromatic groups at bay position of PDI molecule (dipyrollo pyrrole as PDI-I, dithieno pyrrole as PDI-II, furopyrazine as PDI-III, naptho thiadiazole as PDI-IV and thiadiazolo pyridine as PDI-V) were investigated for photovoltaic applications. Optoelectronic properties of investigated molecules were studied using DFT methods at B3LYP/6-31G (d, p) level of theory. Among investigated molecules, PDI-I showed the smallest Eg than those of reference (R) and PDI molecules. The absorption spectra of PDI-I displayed bathochromic shift of 107 nm as compared to R. All investigated molecules PDI-I, PDI-II, PDI-III, PDI-IV and PDI-V also resulted a significant bathochromic shift of 308, 151, 148, 75 and 61 nm, respectively than that of PDI molecule. The reorganization energy analysis indicated that PDI-I and PDI-II could act as excellent hole transporting materials while PDI-III and PDI-IV as excellent electron transporting materials. However, PDI-V acted as ambipolar due to comparable λ e and λ h values. All investigated PDI-I to PDI-V molecules could act as suitable acceptors with previously designed X1 and X2 donors and their V oc ranged from 0.97-1.51 V with X1 and from 0.80-1.34 V with X2. In a nutshell, this computational analysis proved that investigated molecules have potential to be used in cost effective and efficient nonfullerene organic solar cell devices.
Energy Level Tuning of Non-Fullerene Acceptors in Organic Solar Cells
Journal of the American Chemical Society, 2015
The use of non-fullerene acceptors in organic photovoltaic devices could lead to enhanced efficiencies due to increased open-circuit voltages (VOC) and improved absorption of solar light. Here we systematically investigate planar heterojunction devices comprising peripherally substituted subphthalocyanines as acceptor, and correlate device performance with heterojunction energetics. Due to a balance between VOC and photocurrent, tuning of the interface energy gap is necessary to optimize power conversion efficiency in these devices. In addition, we explore the role of the charge transport layers in the device architecture. It is found that non-fullerene acceptors require adjusted buffer layers with aligned electron transport levels to enable efficient charge extraction, while the insertion of an exciton blocking layer at the anode interface further boosts photocurrent generation. These adjustments result in a planar heterojunction OPV device with 6.9% efficiency and a VOC above 1 V.
Non-fullerene acceptor organic photovoltaics with intrinsic operational lifetimes over 30 years
Nature Communications, 2021
Organic photovoltaic cells (OPVs) have the potential of becoming a productive renewable energy technology if the requirements of low cost, high efficiency and prolonged lifetime are simultaneously fulfilled. So far, the remaining unfulfilled promise of this technology is its inadequate operational lifetime. Here, we demonstrate that the instability of NFA solar cells arises primarily from chemical changes at organic/inorganic interfaces bounding the bulk heterojunction active region. Encapsulated devices stabilized by additional protective buffer layers as well as the integration of a simple solution processed ultraviolet filtering layer, maintain 94% of their initial efficiency under simulated, 1 sun intensity, AM1.5 G irradiation for 1900 hours at 55 °C. Accelerated aging is also induced by exposure of light illumination intensities up to 27 suns, and operation temperatures as high as 65 °C. An extrapolated intrinsic lifetime of > 5.6 × 104 h is obtained, which is equivalent to...
ACS Omega, 2022
In the present work, five novel non-fullerene acceptor molecules are represented to explore the significance of organic solar cells (OSCs). The electro-optical properties of the designed A−D−A-type molecules rely on the central core donor moiety associated with different halogen families such as fluorine, chlorine, and bromine atoms and acyl, nitrile, and nitro groups as acceptor moieties. Among these, M1 exhibits the maximum absorption (λ max) at 728 nm in a chloroform solvent as M1 has nitro and nitrile groups in the terminal acceptor, which is responsible for the red shift in the absorption coefficient as compared to R (716 nm). M1 also shows the lowest value of the energy band gap (2.07 eV) with uniform binding energy in the range of 0.50 eV for all the molecules. The transition density matrix results reveal that easy dissociation of the exciton is possible in M1. The highest value of the dipole moment (4.6 D) indicates the significance of M4 and M2 in OSCs as it reduces the chance of charge recombination. The low value of λ e is given by our designed molecules concerning reference molecules, indicating their enhanced electron mobility. Thus, these molecules can serve as the most economically efficient material. Hence, all newly designed non-fullerene acceptors provide an overview for further development in the performance of OSCs.
International Journal of Molecular Sciences
The introduction of the IDIC/ITIC families of non-fullerene acceptors has boosted the photovoltaic performances of bulk-heterojunction organic solar cells. The fine tuning of the photophysical, morphological and processability properties with the aim of reaching higher and higher photocurrent efficiencies has prompted uninterrupted worldwide research on these peculiar families of organic compounds. The main strategies for the modification of IDIC/ITIC compounds, described in several contributions published in the past few years, can be summarized and classified into core modification strategies and end-capping group modification strategies. In this review, we analyze the more recent advances in this field (last two years), and we focus our attention on the molecular design proposed to increase photovoltaic performance with the aim of rationalizing the general properties of these families of non-fullerene acceptors.
Optical and Quantum Electronics
Non fullerene small acceptor molecules in organic photovoltaics are proven beneficial than the traditional fullerene based acceptors for their fine contribution in organic solar cells. Researchers are constantly doing efforts for designing novel acceptor materials with promising photovoltaic properties. Designing of novel molecules by end-capped modifications is a convenient strategy to obtain high efficiency acceptor molecules for OSCs. Herein, we studied optoelectronic characteristics of five novel acceptor-donor-core-donor-acceptor configured small acceptor molecules (S1-S5) after end-capped modifications of recently synthesized DF-PCIC molecule. Designed molecules S1-S5 consist of 1,4-difluorobenzene (as central core), 4,4-bis(2-ethylhexyl)-2,6-dimethyl-4H-cyclopenta[1,2-b:5,4-b′]dithiophene as donor which directly attached with different end-capped acceptors. The electronic and optical properties of newly designed (S1-S5) molecules are examined and compared with reference molecule with the aid of DFT and TD-DFT. Certain key parameters like frontier molecular orbitals analysis, density of states, dipole moment, binding energy along Electronic supplementary material The online version of this article (