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AbstractOrganic photovoltaics (OPV) have attracted great interest as a solar cell technology with appealing mechanical, aesthetical, and economies‐of‐scale features. To drive OPV toward economic viability, low‐cost, large‐scale module production has to be realized in combination with increased top‐quality material availability and minimal batch‐to‐batch variation. To this extent, continuous flow chemistry can serve as a powerful tool. In this contribution, a flow protocol is optimized for the high performance benzodithiophene–thienopyrroledione copolymer PBDTTPD and the material quality is probed through systematic solar‐cell evaluation. A stepwise approach is adopted to turn the batch process into a reproducible and scalable continuous flow procedure. Solar cell devices fabricated using the obtained polymer batches deliver an average power conversion efficiency of 7.2 %. Upon incorporation of an ionic polythiophene‐based cathodic interlayer, the photovoltaic performance could be enhanced to a maximum efficiency of 9.1 %.

Abstract Document bibliographic coupling analysis was applied to a dataset of 23,953 journal papers in order to provide an overview of topics that were present in the academic literature on organic solar cells (OSCs) and perovskite solar cells (PvSCs) during the period of 2008–2017. Ten yearly networks were constructed by linking documents based on shared references, and clusters of closely connected papers were identified as the representations of topics in OSC and PvSC research. Next, 1,437 document titles were read in order to label the 80 most relevant clusters, together containing 11,352 papers. The resulting cluster labels show that research focused on bulk heterojunction polymer/fullerene solar cells in the beginning of the studied period, that OSC material development topics became more important in the middle of the decade, and that continued efforts to improve power conversion efficiencies spurred the rise of new concepts like PvSCs, fullerene-free OSCs, and ternary OSCs in the later years. While traditional literature reviews are valuable for in-depth reviews of specific topics, bibliometric reviews based on document bibliographic coupling are better suited for broad research synthesis. By leveraging the relationships present within the body of literature, they can objectively present the topic structure of large research domains.

Abstract P3HT:PCBM blends applied as active layers for bulk heterojunction organic solar cells generally show unstable morphologies upon prolonged thermal annealing, severely limiting the lifetime of the devices. As such, the thermodynamic instability of the blend is a limiting factor in the overall performance of organic photovoltaics, and a strong disadvantage in the fierce competition with other photovoltaic technologies. This paper shows whether different blend preparation conditions and intrinsic structural changes in the side chains of poly(3-alkylthiophene) (P3AT) derivatives can influence the thermal stability of the resulting solar cells. A combination of Bright Field Transmission Electron Microscopy (BFTEM) and the analysis of Selected Area Electron Diffraction (SAED) patterns revealed that the investigated preparation conditions do not really affect the thermal stability, whereas the introduction of a small ratio (10%) of specific functional moieties in the side chains of random P3AT copolymers does improve the thermal stability significantly. It was demonstrated that demixing of the blend components upon prolonged thermal annealing is strongly delayed in the functionalized P3AT:PCBM blends. The enhanced thermal stability was confirmed by in-situ monitoring of the short circuit current of organic solar cells based on the respective active layers. The introduction of functionalized side chains hence represents an attractive approach to increase the operational stability of organic photovoltaics based on the bulk heterojunction concept.

Ladder-type extension of a push–pull donor polymer affords enhanced peak external quantum efficiencies in microcavity organic photodetectors, with detectivities ranging from 1.07 × 1012 to 1.82 × 1010 Jones in the 900–1400 nm regime.

Abstract Three distinct low bandgap copolymers are synthesized by the combination of N -(2′-propylpentanoyl)dithieno[3,2- b :2′,3′- d ]pyrrole (DTP) and (fluorinated) 2,3-bis[5′-(2”-ethylhexyl)thiophen-2′-yl]quinoxaline (Qx) and these PDTPQx derivatives are investigated as electron donor materials in bulk heterojunction polymer solar cells. Due to the DTP N-acylation and the introduction of the Qx units, both the open-circuit voltage (Voc) and the short-circuit current density (Jsc) increase compared to previous devices based on DTP-type donor polymers. Organic solar cells with an average Voc of 0.67 V, a Jsc of 12.57 mA/cm² and a fill factor of 0.54 are obtained, affording a power conversion efficiency of 4.53% (4.81% for the top-performing device), a record value for (N-acyl-)DTP-based polymer solar cells devoid of special interlayer materials. Despite further enhancement of the Voc, the solar cell efficiency declines for the fluorinated PDTPQx copolymers because of the inability to achieve a finely intermixed bulk heterojunction blend nanomorphology.

AbstractIn the field of polymer solar cells, improving photovoltaic performance has been the main driver over the past decade. To achieve high power conversion efficiencies, a plethora of new photoactive donor polymers and fullerene derivatives have been developed and blended together in bulk heterojunction active layers. Simultaneously, further optimization of the device architecture is also of major importance. In this respect, we report on the use of specific types of electron transport layers to boost the inherent I–V properties of polymer solar cell devices, resulting in a considerable gain in overall photovoltaic output. Imidazolium‐substituted polythiophenes are introduced as appealing electron transport materials, outperforming the currently available analogous conjugated polyelectrolytes, mainly by an increase in short‐circuit current. The molecular weight of the ionic polythiophenes has been identified as a crucial parameter influencing performance.