Recent Advances in Bulk Heterojunction Polymer Solar Cells

Technological deployment of organic photovoltaic modules requires improvements in device light-conversion efficiency and stability while keeping material costs low. Here we demonstrate highly efficient and stable solar cells using a ternary approach, wherein two non-fullerene acceptors are combined with both a scalable and affordable donor polymer, poly(3-hexylthiophene) (P3HT), and a high-efficiency, low-bandgap polymer in a single-layer bulk-heterojunction device. The addition of a strongly absorbing small molecule acceptor into a P3HT-based non-fullerene blend increases the device efficiency up to 7.7 ± 0.1% without any solvent additives. The improvement is assigned to changes in microstructure that reduce charge recombination and increase the photovoltage, and to improved light harvesting across the visible region. The stability of P3HT-based devices in ambient conditions is also significantly improved relative to polymer:fullerene devices. Combined with a low-bandgap donor polymer (PBDTTT-EFT, also known as PCE10), the two mixed acceptors also lead to solar cells with 11.0 ± 0.4% efficiency and a high open-circuit voltage of 1.03 ± 0.01 V. Ternary organic blends using two non-fullerene acceptors are shown to improve the efficiency and stability of low-cost solar cells based on P3HT and of high-performance photovoltaic devices based on low-bandgap donor polymers.

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Reducing the efficiency–stability–cost gap of organic photovoltaics with highly efficient and stable small molecule acceptor ternary solar cells

Organic solar cells (OSCs) present some advantages, such as simple preparation, light weight, low cost and large-area flexible fabrication, and have attracted much attention in recent years. Although the power conversion efficiencies have exceeded 10%, the inferior device stability still remains a great challenge. In this review, we summarize the factors limiting the stability of OSCs, such as metastable morphology, diffusion of electrodes and buffer layers, oxygen and water, irradiation, heating and mechanical stress, and survey recent progress in strategies to increase the stability of OSCs, such as material design, device engineering of active layers, employing inverted geometry, optimizing buffer layers, using stable electrodes and encapsulation. Some research areas of device stability that may deserve further attention are also discussed to help readers understand the challenges and opportunities in achieving high efficiency and high stability of OSCs towards future industrial manufacture.

Stability of organic solar cells: challenges and strategies

Improving the long-term stability of perovskite solar cells is critical to the deployment of this technology. Despite the great emphasis laid on stability-related investigations, publications lack consistency in experimental procedures and parameters reported. It is therefore challenging to reproduce and compare results and thereby develop a deep understanding of degradation mechanisms. Here, we report a consensus between researchers in the field on procedures for testing perovskite solar cell stability, which are based on the International Summit on Organic Photovoltaic Stability (ISOS) protocols. We propose additional procedures to account for properties specific to PSCs such as ion redistribution under electric fields, reversible degradation and to distinguish ambient-induced degradation from other stress factors. These protocols are not intended as a replacement of the existing qualification standards, but rather they aim to unify the stability assessment and to understand failure modes. Finally, we identify key procedural information which we suggest reporting in publications to improve reproducibility and enable large data set analysis. Reliability of stability data for perovskite solar cells is undermined by a lack of consistency in the test conditions and reporting. This Consensus Statement outlines practices for testing and reporting stability tailoring ISOS protocols for perovskite devices.

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Consensus statement for stability assessment and reporting for perovskite photovoltaics based on ISOS procedures

This Review highlights the large number of methods to exploit colloidal assembly of comparably simple particles with nano- to micrometer dimensions in order to access complex structural hierarchies from nanoscopic over microscopic to macroscopic dimensions

Advances in colloidal assembly: the design of structure and hierarchy in two and three dimensions.

Electrophilic Fluorination of Graphitic Carbon for Enhancement in Electric Double‐Layer Capacitance

Ultrasensitive Organic Humidity Sensor with High Specificity for Healthcare Applications

The disposal of organic waste materials such as polymers is a serious problem to natural ecosystems as some of them can be non-biodegradable and potentially toxic. Thus, there is immense interest i...

Ni ink-catalyzed conversion of a waste polystyrene−sugar composite to graphitic carbon for electric double-layer supercapacitors

Fabrication protocols of transparent conducting electrodes (TCEs), including those which produce TCEs of high values of figure of merit, often fail to address issues of scalability, stability, and ...

Scalable Fabrication of Scratch-Proof Transparent Al/F-SnO2 Hybrid Electrodes with Unusual Thermal and Environmental Stability.

Rotational reorientation times of a newly synthesized 2,5-bis(phenylethynyl)1,4-bis(dodecyloxy) benzene (DDPE) are experimentally determined in series of n-alkanes by employing steady state and time resolved fluorescence depolarization technique with a view to understand rotational dynamics of large non-polar solute molecule in non-polar solvents and few general solvents of different sizes and varying viscosity. It is observed that rotational reorientation times vary linearly as function of viscosity. The hydrodynamic stick condition describes the experimental results at low viscosities while the results tend to deviate significantly from it at higher viscosities. This is attributed to the possibility of long chains in solvents hosting a variety of chain defects (end-gauche, double-gauche, all-trans, kink, etc.) thereby reducing the effective length of the molecule, leading to a slightly reduced friction. The experimental results are compared with the predictions of Stokes-Einstein-Debye (SED) hydrodynamic theory as well as the quasi-hydrodynamic theories of Gierer-Wirtz (GW) and Dote-Kivelson-Shwartz (DKS). The predictions from these theories underestimate τr in the solvents employed in the study.

Ritu Gupta

Papers

Electrophilic Fluorination of Graphitic Carbon for Enhancement in Electric Double‐Layer Capacitance

Ultrasensitive Organic Humidity Sensor with High Specificity for Healthcare Applications

Ni ink-catalyzed conversion of a waste polystyrene−sugar composite to graphitic carbon for electric double-layer supercapacitors

Scalable Fabrication of Scratch-Proof Transparent Al/F-SnO2 Hybrid Electrodes with Unusual Thermal and Environmental Stability.

Rotational Diffusion of a New Large Non Polar Dye Molecule in Alkanes