P3HT-based Polymer Solar Cells Research Articles

Enhanced performance of P3HT-based non-fullerene polymer solar cells by optimizing film morphology using non-halogenated solvent

Increasing research interests have been paid to developing efficient polymer solar cells by using integrating non-fullerene acceptors with poly (3-hexylthiophene) (P3HT), owing to the low-cost, promising performance and excellent stability. Here we systematically studied how processing solvents influence the overall performances of polymer solar cells using P3HT as the electron donor. It is very interesting to note that the devices processed with the non-halogenated solvent, 2-methylanisole in presence of 1-methylnaphthalene as solvent additive, exhibit reduced bimolecular and trap-assisted monomolecular recombination, facile charge extraction and enhanced charge carrier mobilities. Careful morphological investigation reveals that the optimizing crystallites, phase purity as well as nanofibrous structure is effective to the enhancement of charge generation and transport. It is also worth noting that these P3HT:O-IDTBR based devices processed with these non-halogenated solvents exhibitean impressive power conversion efficiency of 7.1% with a high fill factor of 75.09% on a device area of 0.05 cm2, and the efficiency remained 6.89% even in a device with large active layer area of 1 cm2, while also showing promising thermal stability. This study provides a new scope of processing P3HT based polymer solar cells by using non-halogenated solvents, which is compatible and has great promise for future applications.

P3HT-Based Polymer Solar Cells with 8.25% Efficiency Enabled by a Matched Molecular Acceptor and Smart Green-Solvent Processing Technology.

A novel molecular acceptor of TrBTIC (2,7,12-tris((2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile-7-benzothiadiazole-2-)truxene) is designed by attaching the 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile-benzothiadiazole (BTIC) electron-deficient unit to an electron-rich truxene core. TrBTIC has excellent solubility in common solvents and features good energy level matching with poly(3-hexylthiophene) (P3HT). Interestingly, P3HT can be readily dissolved in warm 1,2,4-trimethylbenzene (TMB), a green solvent, but crystallizes slowly with long-term aging in TMB at room temperature. A prephase separation can thus occur before active blend film deposition, and the separation degree can be easily controlled by varying the aging time. After 40 min of aging, the resulting active blend has the most appropriate phase separation with uniform nanowires, which forms favorable interpenetrating networks for exciton dissociation and charge transport. As a result, the device performance is improved from 6.62% to 8.25%. Excitingly, 8.25% is a new record for P3HT-based solar cells. The study not only provides an efficient nonfullerene acceptor for matching P3HT donors but also develops a promising processing technology to realize high-performance P3HT-based polymer solar cells with an efficiency over 8%.

Impact of P3HT materials properties and layer architecture on OPV device stability

We report a cooperative study conducted between different laboratories to investigate organic solar cell degradation with respect to P3HT material properties and different solar cell architectures. Various batches of P3HT were collected from different suppliers reflecting commercial availability as well as properties variability. Among the materials properties explicitly considered were the molar mass, dispersity, regio-regularity, impurities by trace metals and intrinsic doping evaluated from radical concentrations. Each of the participating laboratories contributing test devices applied their own layer stack, i.e. their own device architecture and layout. This variation was appreciated as another parameter for evaluation. Even though a large amount of devices failed due to extrinsic degradation effects, indeed, some materials properties were found to be more important than others for obtaining long lifetimes and high stability of P3HT-based polymer solar cells.

Formulation of PC71BM isomers in P3HT-based polymer solar cells

Formulation engineering, featuring with different ingredients combined, is a useful strategy for making efficient electronic acceptors because it can achieve effects that cannot be obtained from its components when these are used singly. Herein, we show a contour plot with different formulations of isomeric phenyl-C71-butyric acid methyl ester (PC71BM) as electron acceptors in poly(3-hexylthiophene) (P3HT):PC71BM polymer solar cells (PSCs). Upon altering fullerene formulation the PCEs change in the range of 0.87–4.01%. The optimized formulation consisting of ~ 80% α-PC71BM, ~ 10% β1-PC71BM, and ~ 10% β2-PC71BM exhibits the best PCE of 4.01%, which mainly benefits from the optimum morphology of P3HT-fullerene heterojunction film. The present work demonstrates a successful strategy by controlling morphology of PC71BM isomers to improve the PCE of P3HT-based PSCs, and consolidates the photovoltaic performance of polymer solar cells heavily dependent on the formulation of fullerene-based electron acceptors.

High-efficiency and air-stable P3HT-based polymer solar cells with a new non-fullerene acceptor.

Solution-processed organic photovoltaics (OPV) offer the attractive prospect of low-cost, light-weight and environmentally benign solar energy production. The highest efficiency OPV at present use low-bandgap donor polymers, many of which suffer from problems with stability and synthetic scalability. They also rely on fullerene-based acceptors, which themselves have issues with cost, stability and limited spectral absorption. Here we present a new non-fullerene acceptor that has been specifically designed to give improved performance alongside the wide bandgap donor poly(3-hexylthiophene), a polymer with significantly better prospects for commercial OPV due to its relative scalability and stability. Thanks to the well-matched optoelectronic and morphological properties of these materials, efficiencies of 6.4% are achieved which is the highest reported for fullerene-free P3HT devices. In addition, dramatically improved air stability is demonstrated relative to other high-efficiency OPV, showing the excellent potential of this new material combination for future technological applications.

The influence of amino group on PCDTBT-based and P3HT-based polymer solar cells: Hole trapping processes

Polymer solar cells (PSCs) based on aliphatic-amino-functionalized materials presented low performance with negligibly small efficiency, the prime mechanism of which is found to be hole trapping induced by the amine end groups. We propose that such hole trapping behavior depends on the relative energetic position of the hole transport states and the trapping states. Herein, we comparatively study the photovoltaic properties of PSCs based on amino-functionalized fullerene derivative blended with poly [N-9′-heptadecanyl-2, 7-carbazole-alt-5, 5-(4′, 7′-di-2-thienyl-2′, 1′, 3′-benzothiadiazole)] (PCDTBT) or poly (3-hexylthiophene) (P3HT). The former polymer has a lower-positioning highest occupied molecular orbital (HOMO) level, whereas the latter has a comparable HOMO level relative to the ionization state of tertiary aliphatic amine in energy. Our investigation confirms our proposition, revealing an ultrafast trapping process in PCDTBT:amino-group-functionalized fullerene derivative film, which seriously crippled hole transport, consequently results in very poor device performance. In contrast, trapping process is almost negligible in P3HT systems.

Synthesis and Characterization of Phenanthrene-substituted Fullerene Derivatives as Electron Acceptors for P3HT-based Polymer Solar Cells

E-mail: dohoonhwang@pusan.ac.krReceived December 3, 2013, Accepted February 6, 20149,10-Bis(bromomethyl)phenanthrene reacted with fullerenes via a Diels-Alder reaction to give phenanthrene-substituted fullerene mono-adducts (PCMA) and bis-adducts (PCBA) as electron acceptors for organicphotovoltaic cells (OPVs). The syntheses of the fullerene derivatives were confirmed by

Scattering or Photoluminescence? Major Mechanism Exploration on Performance Enhancement in P3HT‐Based Polymer Solar Cells with NaYF4:2% Er3+, 18% Yb3+ Upconverting Nanocrystals

Scattering or Photoluminescence? Major Mechanism Exploration on Performance Enhancement in P3HT‐Based Polymer Solar Cells with NaYF₄:2% Er³⁺, 18% Yb³⁺ Upconverting Nanocrystals

Photoinduced Charge Transfer in Donor–Acceptor (DA) Copolymer: Fullerene Bis-adduct Polymer Solar Cells

Polymer solar cells (PSCs) consisting of fullerene bis-adduct and poly(3-hexylthiophene) (P3HT) blends have shown higher efficiencies than P3HT:phenyl C(61)-butyric acid methyl ester (PCBM) devices, because of the high-lying lowest unoccupied molecular orbital (LUMO) level of the fullerene bis-adducts. In contrast, the use of fullerene bis-adducts in donor-acceptor (DA) copolymer systems typically causes a decrease in the device's performance due to the decreased short-circuit current (J(SC)) and the fill factor (FF). However, the reason for such poor performance in DA copolymer:fullerene bis-adduct blends is not fully understood. In this work, bulk-heterojunction (BHJ)-type PSCs composed of three different electron donors with four different electron acceptors were chosen and compared. The three electron donors were (1) poly[(4,8-bis-(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene)-2,6-diyl-alt-(5-octylthieno[3,4-c]pyrrole-4,6-dione)-1,3-diyl] (PBDTTPD), (2) poly[(4,8-bis-(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene)-2,6-diyl] (PBDTTT-C), and (3) P3HT polymers. The four electron acceptors were (1) PCBM, (2) indene-C(60) monoadduct (ICMA), (3) indene-C(60) bis-adduct (ICBA), and (4) indene-C(60) tris-adduct (ICTA). To understand the difference in the performance of BHJ-type PSCs for the three different polymers in terms of the choice of fullerene acceptor, the structural, optical, and electrical properties of the blends were measured by the external quantum efficiency (EQE), photoluminescence, grazing incidence X-ray scattering, and transient absorption spectroscopy. We observed that while the molecular packing and optical properties cannot be the main reasons for the dramatic decrease in the PCE of the DA copolymers and ICBA, the value of the driving force for charge transfer (ΔG(CT)) is a key parameter for determining the change in J(SC) and device efficiency in the DA copolymer- and P3HT-based PSCs in terms of fullerene acceptor. The low EQE and J(SC) in PBDTTPD and PBDTTT-C blended with ICBA and ICTA were attributed to an insufficient ΔG(CT) due to the higher LUMO levels of the fullerene multiadducts. Quantitative information on the efficiency of the charge transfer was obtained by comparing the polaron yield, lifetime, and exciton dissociation probability in the DA copolymer:fullerene acceptor films.

Efficiency enhancement in P3HT-based polymer solar cells with a NaYF4:2% Er3+, 18% Yb3+ up-converter

The commonly used donor material poly(3-hexylthiophene) (P3HT) confines the power conversion efficiency (PCE) in P3HT-based polymer solar cells due to its relatively large bandgap of ∼1.9 eV and the resultant limited absorption wavelength region of less than 650 nm. In this communication, the highly efficient up-conversion (UC) material NaYF4:2% Er3+, 18% Yb3+, converting near-infrared radiation into green and red emissions, is introduced into a P3HT/P3HT:[6,6] phenyl C61 butyric acid methyl ester (PC61BM) bulk heterojunction solar cell, referred to as a “bilayer cell”, to compensate for the non-absorbable wavelength region of P3HT. With an optimal UC doping concentration of 11.7% (weight ratio of UC to P3HT) in the P3HT matrix, the short-circuit current density and PCE for UC-doped bilayer cell are as high as 10.89 mA cm−2 and 3.62%, about 16.6% and 10.7% higher than the P3HT/P3HT:PC61BM bilayer cell and 22.4% and 16.4% higher than the standard P3HT:PC61BM bulk heterojunction one, respectively, although the fill factor in the UC-doped bilayer cell shows a slight decrease. The research result demonstrates that both the emission and the scattering of UC nanoparticles are beneficial to the enhancement of the solar cell's electrical performances.