Long-term efficient organic photovoltaics based on quaternary bulk heterojunctions

Abstract

A major impediment to the commercialization of organic photovoltaics (OPVs) is attaining long-term morphological stability of the bulk heterojunction (BHJ) layer. To secure the stability while pursuing optimized performance, multi-component BHJ-based OPVs have been strategically explored. Here we demonstrate the use of quaternary BHJs (q-BHJs) composed of two conjugated polymer donors and two fullerene acceptors as a novel platform to produce high-efficiency and long-term durable OPVs. A q-BHJ OPV (q-OPV) with an experimentally optimized composition exhibits an enhanced efficiency and extended operational lifetime than does the binary reference OPV. The q-OPV would retain more than 72% of its initial efficiency (for example, 8.42–6.06%) after a 1-year operation at an elevated temperature of 65 °C. This is superior to those of the state-of-the-art BHJ-based OPVs. We attribute the enhanced stability to the significant suppression of domain growth and phase separation between the components via kinetic trapping effect.

The role of the third component in ternary organic solar cells

“…The highly stable glassy nanostructure of D:A1:A2 ternary mixtures increases the configurational entropy upon mixing of the A1:A2 components and reduces both the rate of phase separation and crystallization 90 . As a proof of concept, a quaternary BHJ based on D1:D2:A1:A2 was designed and found to retain >72% of its initial efficiency after 1 year of thermal degradation owing to dual control of phase separation and crystallization 87 . The third component in ternary blends can induce specific molecular interactions in the BHJ, which can suppress molecular diffusion and reduce the  values of the corresponding binary systems.…”

“…The models used to explain the operation of TSCs typically describe the location of the third component in the blend and the effect of mixing the third material with one of the other components (donor or acceptor). Third, we assess the role of the third component in influencing the electronic energy level alignment, spectral coverage, charge recombination and nanomorphology of ternary blends and devices 35,[70][71][72][73][74][75][81][82][83][84][85][86][87][88][89] . We also consider the stability of the active-layer materials and devices as well as the recent progress in the development of ternary blends to help overcome the degradation and/or reliability issues of binary solar cells 35,90 .…”

The Crucial Role of Quaternary Mixtures of Active Layer in Organic Indoor Solar Cells

“…Their study explained that the use of a cascade energy driver can enhance the driving force for charge transfer [16]. A quaternary solar cell was reported to show good BHJ morphology and charge transport [17]. This article also illustrated that the quaternary solar cell showed improved stability.…”

“…Multi-coefficient fitting of the complex refractive indices and meshing of the device structure were utilized as necessary. The quaternary BHJ ratio was set at 1:9:3:12 of PCDTBT:PTB7:PC 61 BM:PC 71 BM, as seen in the reference article by Nam et al [17]. For the single bulk heterojunction photovoltaic structure we utilized PTB7:PC 71 BM and PCDTBT:PC 71 BM-based device structures.…”

Development of a Library of Novel Compounds for Use in Organic Solar Cells

“…Particularly effective on systems containing materials with a glass transition temperature (Tg), thermally induced reorganisation processes enable significant changes to the BHJ morphology. 194,[197][198][199][200] A strong relationship between the annealing procedure and I-V characteristics is demonstrated across a number of systems due to crystallisation and diffusion of the active layer materials. [201][202][203][204][205][206][207][208][209] High boiling solvent additives (e.g., diiodooctane (DIO)) are added to adjust the rate at which one or more components are deposited from solution.…”