Recent Advances in Bulk Heterojunction Polymer Solar Cells

Organic solar cells have desirable properties, including low cost of materials, high-throughput roll-to-roll production, mechanical flexibility and light weight. However, all top-performance devices are at present processed using halogenated solvents, which are environmentally hazardous and would thus require expensive mitigation to contain the hazards. Attempts to process organic solar cells from non-halogenated solvents lead to inferior performance. Overcoming this hurdle, here we present a hydrocarbon-based processing system that is not only more environmentally friendly but also yields cells with power conversion efficiencies of up to 11.7%. Our processing system incorporates the synergistic effects of a hydrocarbon solvent, a novel additive, a suitable choice of polymer side chain, and strong temperature-dependent aggregation of the donor polymer. Our results not only demonstrate a method of producing active layers of organic solar cells in an environmentally friendly way, but also provide important scientific insights that will facilitate further improvement of the morphology and performance of organic solar cells. The processing of high-performance organic solar cells usually requires environmentally hazardous solvents. Now, hydrocarbon-based processing is shown to achieve relatively high performance in a more environmentally friendly way.

Efficient organic solar cells processed from hydrocarbon solvents

A nonfullerene-based polymer solar cell (PSC) that significantly outperforms fullerene-based PSCs with respect to the power-conversion efficiency is demonstrated for the first time. An efficiency of >11%, which is among the top values in the PSC field, and excellent thermal stability is obtained using PBDB-T and ITIC as donor and acceptor, respectively.

Fullerene-Free Polymer Solar Cells with over 11% Efficiency and Excellent Thermal Stability

We thank the University of St Andrews for support. EZ-C thanks the Leverhulme Trust for financial support (RPG-2016-047). and the EPSRC (EP/P010482/1) for financial support.

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Purely Organic Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes.

ConspectusThe active layer in a solution processed organic photovoltaic device comprises a light absorbing electron donor semiconductor, typically a polymer, and an electron accepting fullerene acceptor. Although there has been huge effort targeted to optimize the absorbing, energetic, and transport properties of the donor material, fullerenes remain as the exclusive electron acceptor in all high performance devices. Very recently, some new non-fullerene acceptors have been demonstrated to outperform fullerenes in comparative devices. This Account describes this progress, discussing molecular design considerations and the structure–property relationships that are emerging.The motivation to replace fullerene acceptors stems from their synthetic inflexibility, leading to constraints in manipulating frontier energy levels, as well as poor absorption in the solar spectrum range, and an inherent tendency to undergo postfabrication crystallization, resulting in device instability. New acceptors have to address ...

Non-Fullerene Electron Acceptors for Use in Organic Solar Cells

Fabrication and Characterization of FAxCs1−xPbI3 Polycrystal Perovskite Solar Cells

Two benzodithiophene (BDT)-based homopolymers which have different mole ratios of poly-ether side chain substitute were synthesized by Stille coupling reaction. 
The polymers show decomposition temperature (T
 d) around 317 °C and optical band gap around 2.2 eV. Solar cell devices with bulk heterojunction structure and field-effect transistors devices were fabricated to evaluate the photovoltaic properties of resultant polymers. Solar cell devices based 
on the polymer with 100 % poly-ether side chain (P1) show low power conversion efficiencies (PCEs) of 0.71 % resulting from the poor morphology of active layer which has rough surface and fairly large domain size due to the high aggregation tendency of P1:PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) blend thin film as active layer in the structure of devices. Polymer with alternating poly-ether and alkoxy chained BDT (P2) and PCBM blend film shows smooth surface and appropriate domain size, which help to enhance the hole transportation and photovoltaic performances. The PCEs of the devices based on P2 reached 2.00 % which is a decent result for BDT-based homopolymer donor with relatively large band gap (ca. 2.2 eV). These two polymers exhibited mobilities of 3.95 × 10−4 and 6.18 × 10−4 cm2/Vs in field-effect transistors, respectively.

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Mingliang Sun

Papers

Fabrication and Characterization of FAxCs1−xPbI3 Polycrystal Perovskite Solar Cells

Hydrophilic poly-ether side-chained benzodithiophene-based homopolymer for solar cells and field-effect transistors

Random terpolymers for high-performance semitransparent polymer solar cells

Asymmetric ITIC acceptor for asymmetric benzodithiophene polymer solar cells

Thieno[2,3-f]benzofuran based donor-acceptor polymer for fullerene-free solar cells