Correlation between P3HT inter-chain structure and Jsc of P3HT:PC[70]BM blends for solar cells

doi:10.1016/j.microrel.2012.11.006

Microelectronics Reliability

Volume 53, Issue 4, April 2013, Pages 560-564

https://doi.org/10.1016/j.microrel.2012.11.006 Get rights and content

Abstract

The nano-morphology of the active layer of organic solar cells has been studied extensively, as well as its link with the open circuit voltage of the device. However, considerably less attention has been dedicated to the relation between the active layer nano-morphology and the device short circuit current density. In this paper we study the relation between variations in the characteristics of the Poly-(3-hexylthiophene-2,5-diyl) (P3HT) chains and the resultant solar cell short circuit current density. We show that the lattice constant between two lamellar structure of P3HT inside the P3HT:Phenyl C₇₀ Butyric Acid Methyl Ester (PC_[70]BM) blend reduced as the PC_[70]BM percent in weight was reduced in the analyzed range. The presence of nano-domains, which can be related to the intensity of the peak, also affects the short circuit current density. In this study the optimum value of the percent in weight of PC_[70]BM, to obtain high short circuit current density was obtained for 1:0.5 ratio in the blend. The distance constant between the lamellar structure of P3HT for each blend made was directly extracted from the Bragg’s law in combination with the μ-XRD analysis. The results were correlated with the electrical characterization for each blend and we found that when decreases the distance between two lamellar structure of P3HT there is a better performance on photovoltaic devices.

Graphical abstract

Highlights

► Relation between J_sc and the interchains distance of the polymer in the active layer is shown. ► Lamellar structure and interchains of P3HT is affected when the PC_[70]BM is increased. ► Peaks in μ-XRD analysis confirm the presence of nano-domains in the polymer active layer.

Introduction

Most bulk heterojunction BHJ organic solar cells use as active layer, a blend of a conjugated polymer and a fullerene. Currently, this kind of organic solar cell is the most promising for the accomplishment of a low cost, light-weight, large area, flexible, easily processed, and renewable energy source [1]. The main progress in bulk heterojunction organic solar cells has been achieved by introducing new materials with low band gap, process and new technologies [2], [3], [4], [5]. Power conversion efficiencies (PCE) above 10% were first reported in 2012 [6]. The PCE of such devices is predominantly influenced by the optical and electronic properties of the donor and acceptor materials and the morphology of the blend controlling the domain size [7], [8], [9].

Having domain sizes well defined in the bulk of the active layer helps to have a good performance on the charge carrier transport across of their respective materials (i.e. holes in donor material and electrons in acceptor material) and finally be collected in their respective metal contacts. Result of the foregoing is a reduction of the charge carrier recombination during the transport, situation that is desirable in the photovoltaic devices.

Although blends of Poly-(3-hexylthiophene-2,5-diyl) (P3HT):Phenyl C₇₀ Butyric Acid Methyl Ester (PC_[70]BM) have been much studied, not enough attention has been paid to the study of P3HT inter-chains with the PC_[70]BM and to the relation between the short circuit current density (J_sc) and the morphology, since the process of the charge generation and separation should strongly depend on the interface properties, while the charge carrier transport will be determined by the bulk properties of the components of the active layer as was describe above.

In this paper we will show that the quantity of fullerene in the blend modifies the interchain distance-spacing (d₁₀₀) in P3HT associated with the interdigitated alkyl chains, which affects the J_sc. The crystalline structure of the active layers were analyzed using micro-X-ray diffraction. This information in combination with the Braggs’ law was used to calculate the distance-spacing in P3HT. The findings in distance-spacing in all blends together with complementary electrical characterization were subsequently correlated with the performance of the organic solar cells.

Section snippets

Experimental

Indium tin oxide (ITO)-coated glass substrates (with nominal sheet resistance of 15 Ohm/square and 120 nm of thickness) were purchased from PsiOTec Ltd. Poly-(Ethylene dioxythiophene) doped with Poly-(Styrene Sulphonic acid) (PEDOT:PSS) FHC was acquired from Ossila Ltd., P3HT (melting point 238 °C, M_w ∼ 17500 g mol⁻¹, 99.995% region-regularity) and PC_[70]BM (M_w ∼ 1030.99 g mol⁻¹) were purchased from Sigma–Aldrich. High-purity (99.99%) silver (Ag) pellets were obtained from Testbourne Ltd., and calcium

Results and discussion

The J–V characteristics of the devices were measured in a sealed capsule under inert nitrogen atmosphere immediately after removing from the vacuum system. The short circuit current, open circuit voltage (V_oc), calculated fill factor (FF) and power conversion efficiency (η%) of the fabricated devices are summarized in Table 1. The extracted parameters of each device under illumination were done using an electrical circuit to model the measured J–V characteristics [11], [12], [13]. Fig. 2 shows

Conclusions

We show that the lattice constant between two lamellar structure of P3HT inside of the blend P3HT:PC_[70]BM of bulk heterojunction composites is affected by the PC_[70]BM amount in the blend. Increasing the amount of PC_[70]BM increases the disorder of the interchains of the polymer in the blend and there is an increase in the charge carrier recombination. The micro-X-ray diffraction showed that the less interchain distance-spacing d₁₀₀ in P3HT of 1.64 nm, corresponded to the blend S1 (1:0.5 wt.%),

Acknowledgements

This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under Grant number TEC2009-09551, TEC2012-34397, CONSOLIDER HOPE Project CSD2007-00007, Generalitat of Catalunya under Project 2009 SGR 549 and CONACYT in Mexico under Project 127978.

References (23)

C.J. Brabec
Organic photovoltaics: technology and market
Sol Energy Mater Sol Cells
(2004)
W. Cai et al.
Polymers solar cells: recent development and possible routes for improvement in the performance
Sol Energy Mater Sol Cells
(2010)
Y. Zhang et al.
Bulk heterojunction solar cells based on a new low-band gap polymer: morphology and performance
Org Electron
(2011)
V.S. Balderrama et al.
Influence of P3HT:PCBM blend preparation on the active layer morphology and cell degradation
Microelectron Reliab
(2011)
J.A. Renz et al.
Multiparametric optimization of polymer solar cells: a rout to reproducible high efficiency
Sol Energy Mater Sol Cells
(2009)
M. Helgesen et al.
Advance materials and processes for polymer solar cell devices
J Mater Chem
(2010)
G. You et al.
Polymer photovoltaic cells: enhanced efficiencies via a network of internal donor–acceptor heterojunctions
Science
(1995)
M. Green et al.
Solar cell efficiency table (version 39)
Res Appl
(2012)
J. Peet et al.
Plastic solar cells: self-assembly of bulk heterojunction nano-materials by spontaneous phase separation
Acc Chem Res
(2009)
M.C. Scharber et al.
Design rules for donors in bulk heterojunction solar cells: towards 10% energy conversion efficiency
Adv Mater
(2006)

S.E. Shaheen et al.

2.5% efficient organic plastic solar cells

J Appl Phys

(2001)

Cited by (27)

Structural modification and conductivity enhancement of NiCl<inf>2</inf> incorporated P3HT: PC<inf>60</inf>BM based organic photoactive layer
2023, Optical Materials
High planar defect and poor crystalline structure in P3HT has limited the device performance of organic photovoltaic. To date, surface modification on the P3HT molecular structure has been introduced to improve its intrinsic properties. In this project, different volume percent of NiCl₂ were incorporated into the P3HT:PC₆₀BM film using a wet chemical approach. The effects on the structural, electrical, and optical properties of the active material after the metal halide incorporation were elucidated. Among the samples, 20 vol% NiCl₂ sample presented the highest C–C intra-ring in raman analysis, which signifies the formation of long conjugate P3HT chain that contributes to a stronger electron phonon coupling and promotes a charge transfer from CC bonds. After the active layer was incorporated with 20 vol% NiCl₂, the surface roughness of the film decreased from (13.8 ± 2.6) nm to (4.2 ± 1.5) nm as compared to pristine P3HT:PC₆₀BM film. The photoabsorbance and electrical conductivity of 20 vol% NiCl₂ sample also increased by 1.8 fold and 47%, respectively. The presence of NiCl₂ can serve as a surface passivator in P3HT interface which eventually reduces the electron organisation energy and increases the charge transport ability in active layer. This novel finding can serve as an alternative to improve the device performance of P3HT-based active material organic solar cells.
Preparation and optical-electronic properties of thin films comprising P3HT and few-layer graphene nanosheets
2023, Materials Science and Engineering: B
The present work investigates the production of thin films from nanocomposites obtained by solution mixing a synthesized P3HT with different proportions of few-layered graphene (FLG) in chloroform and its influence on crystallography and light absorption in the visible region. Commercial FLG produced through exfoliation in the liquid phase assisted by a non-anionic surfactant was employed, being a material not yet tested for the production of nanocomposites, let alone to be applied in photovoltaic cells. The deposition of thin films was evaluated at low (1000 rpm) and high (2500 rpm) rotation speeds in a dynamic and static deposition process. In addition, the annealing heat treatment in the optimized thin films was evaluated. The results showed that the P3HT was synthesized with suitable molar mass, regioregularity, and thermal resistance as characterized by the analyses of gel permeation chromatography (GPC), ¹H-nuclear magnetic resonance (¹H NMR), and thermogravimetric analysis (TGA). The thin films produced showed that the FLG enlarged and strengthened the P3HT absorption, increasing the absorption region by up to 34 % in addition to improving the resolution of the absorption peaks favoring the π-π* transition, which is important for the photovoltaic effect. By the X-ray diffraction analysis, it can be suggested that incorporating the FLG improves the charge mobility as there was an increase in the crystallite size without changing the interplanar distance. Based on these results, it can be suggested that P3HT/FLG nanocomposites are promising for application in both the active and hole transport layers of solar cells.
Modulation of optical, photophysical and electrical properties of poly(3-hexylthiophene) via Gd:CdS nanoparticles
2022, Optik
Citation Excerpt :
Additional diffraction peaks of low intensity observed at 2θ = 10.87°, and 16.19° which are corresponds to (200) and (300) planes of P3HT, signifying the crystallinity of fabricated films [38]. The diffraction peak observed at 23.66° is corresponds to the (010) plane, originated due to π–π interchain stacking [39,40]. Further, the diffraction spectra of drop-casted P3HT/Gd:CdS hybrid films exhibits additional diffraction peaks at 25.31°, 26.62°, 28.13°, 43.69°, 48.19° and 52.21° which are respectively corresponds to (100), (002), (101), (110), (103) and (112) planes of CdS nanoparticles according to JCPDS#41–1049 [35].
Herein, the impact of Gadolinium (Gd) doped cadmium sulphide (CdS) nanoparticles on the structural, optical, photophysical and electrical properties of poly(3-hexylthiophene) (P3HT) thin films have been investigated. The structural, morphological and vibrational properties of fabricated films were probed by measuring X-ray diffraction spectra, scanning electron microscope images and FT-Raman spectra, respectively. The absorption spectra of P3HT thin films was noted to be red shifted and energy bandgap slightly decreases with incorporation of Gd:CdS nanoparticles. The extinction coefficient (k), refractive index (n) and dielectric constants (ε_r, ε_i) of pure and hybrid films were extracted from spectroscopic ellipsometer data fitted by new amorphous dispersion model (for P3HT) and Adachi-New Forouhi dispersion model (for CdS) and noted that the optical constants decreases with increase of Gd:CdS nanoparticles concentrations. The photoluminescence intensity of P3HT/Gd:CdS films was quenched as compare to pristine P3HT, also an additional bands observed in hybrid films corresponds to emission from Gd:CdS nanoparticles. The average fluorescence life times of pristine P3HT thin films was evaluated to be 154 ps which drop to 109 ps for hybrid film, ascribes to formation of additional decay paths created due to Gd:CdS doping. The electrical resistivity (ρ) and mobility (μ) of P3HT films were measured from Hall Effect systems and noted to be decreases for hybrid films whereas charge carrier concentration (n_C) and sheet resistance (R_S) increases.
Elucidating the impact of PbI<inf>2</inf> on photophysical and electrical properties of poly(3-hexythiophene)
2020, Materials Science in Semiconductor Processing
Citation Excerpt :
The spectra of pristine P3HT did not exhibit any clear peaks either due to amorphous nature of polymer film or might be low film thickness of the order of 60–80 nm. Instead, XRD spectra of pure P3HT only shows a broad hump starting from 2θ ≅ 18°–37° with a pinnacle at 24° corresponds to the plane at (01 0) and is related to face-to-face packing ring d010 of P3HT [44]. The diffraction pattern of P3HT/PbI2 thin films shows certain characteristic peaks of PbI2 and intensity of these peaks increases with the increase of PbI2 content.
Owing to high absorption coefficient, controlled morphology and high charge carrier mobility, poly (3-hexylthiophene) (P3HT) is a well-known donor material for organic solar cells, but device efficiency is still average compared to other conjugated polymers such as PDCBT, PB3T, P12 etc. The present research aims to enhance the optoelectrical properties of P3HT thin films through the incorporation of PbI₂ in P3HT. Herein, novel P3HT/PbI₂ hybrid thin films fabricated and the effect of different PbI₂ doping levels on structural, spectroscopic and electrical properties of P3HT was elucidated. Incorporation of PbI₂ in P3HT matrix was confirmed through the observation of characteristic peaks of PbI₂ in XRD and Raman spectra of P3HT. Surface morphology of fabricated films were investigated by SEM and reveals that the morphology of hybrid film entirely changed for higher PbI₂ concentration. Fabricated films were then characterized through a number of spectroscopic techniques including: UV–Visible absorption, fluorescence and ellipsometer spectroscopy. The optical parameters: dielectric constant (ε_r), dielectric loss (ε_i), extinction coefficient (k) and refractive index (n) were extracted from the fitting of Ellipsometer data by using mathematical models. It was found that the incorporation of PbI₂ in P3HT leads to decrease of the optical band gap from 1.94 eV to 1.79 eV and increases of the refractive of P3HT thin films. The effective life time of charge carrier was found to be decreases from 106 ps for pristine P3HT to 15.6 ps for P3HT/PbI₂. Hall Effect measurement shows enhancement in carrier concentrations from 7.62 × 10¹⁴ cm⁻³ (pristine P3HT) to 4.51 × 10¹⁸ cm⁻³ (P3HT/PbI₂), decrease of electrical resistivity from 3.68 × 10⁴ Ω cm (pristine P3HT) to 1.00 × 10⁴ Ω cm (P3HT/PbI₂) and decrease in carrier mobility from 2.23 × 10⁻¹ (pristine P3HT) to 1.38 × 10⁻³ cm²/Vs (P3HT/PbI₂).
High efficient and stabilized photovoltaics via morphology manipulating in active layer by rod-coil block copolymers comprising different hydrophilic to hydrophobic dielectric blocks
2016, European Polymer Journal
Citation Excerpt :
Therefore, by moving towards more packed P3HT chains in the hexyl side chain direction, the opportunity of formation of the face-on crystallites increased. A better performance was previously reported for the OPV devices by decreasing the distance between the P3HT lamellar structures [106]. In 60 wt%, the hole mobility and Jsc peaked at 4.5 × 10−3 cm2/V s and 11.68 mA/cm2, respectively (Fig. 8(a)).
The poly(3-hexylthiophene) (P3HT)-based block copolymers were synthesized with hydrophilic and hydrophobic dielectric blocks including poly(ethylene glycol) (PEG), poly(methyl methacrylate) (PMMA), and poly(styrene) (PS), and employed as morphology modifiers (10–80 wt%) in P3HT: phenyl-C71-butyric acid methyl ester (PC71BM) bulk heterojunction (BHJ) solar cells. The advantages and drawbacks of the coily blocks were also outlined from perspective of photovoltaic characteristics. A novel matrix-bridged disperses model was proposed to map out well-connected BHJ networks, which was consistent with the scattering data. Rod-coil block copolymers simultaneously controlled some main properties, i.e., crystallinity, d-spacing, domain sizes, and stability. Hydrophobic-based block copolymers (P3HT-b-PS and P3HT-b-PMMA) increased crystallinity, P3HT crystallite size, and PC71BM cluster size and decreased d-spacings. This reflected larger and denser P3HT crystallites and coarser and more packed PC71BM clusters. P3HT crystallites grew up to ∼60 and 30 nm in (1 0 0) and (0 2 0) directions, respectively. In 30 wt% of P3HT₇₁₅₀-b-PS, PC71BM clusters were also the largest (=38.87 nm). A fully interdigitated hexyl chains (10.05 Å) was acquired in 80 wt% of P3HT₇₁₅₀-b-PS. Impressing trends of the P3HT-b-PMMA copolymers resembled that of P3HT-b-PS ones, but with a smoother slope. In contrast, hydrophilic-based block copolymers (P3HT-b-PEG and P3HT-b-PEG-b-P3HT) resulted in finer and looser P3HT crystallites and PC71BM clusters. The largest d-spacings in the directions of the hexyl side chains (=19.97 Å) and π-π stacking (=4.95 Å) were detected in 80 wt% of P3HT₇₁₅₀-b-PEG₇₅₀. The lowest (=3.51 Å) and highest (=5.63 Å) d-spacings for PC71BM clusters appeared in 80 wt% of P3HT₇₁₅₀-b-PS and P3HT₇₁₅₀-b-PEG₇₅₀, respectively. Unlike PEG-based block copolymers, in P3HT-b-PS and P3HT-b-PMMA ones, lower P3HT molecular weights conduced to higher power conversion efficiencies (PCE = 4.43%). The short current density (J_sc = 11.68 mA/cm²), open circuit voltage (V_oc = 0.63 V), and fill factor (FF = 63%) were maximized in well-modified photovoltaic devices.
Investigation of the usage of centrifuging waste of mineral wool melt (CMWW), contaminated with phenol and formaldehyde, in manufacturing of ceramic products
2014, Waste Management
Citation Excerpt :
X-ray analysis was performed by using X-ray diffractometer DRON-7. Distance between atomic planes d estimated according to Bragg’s law (Balderrama et al., 2013). The microstructure of the formed CMWW waste and ceramic body was investigated with the scanning electron microscopy EVO 50 EP.
Large amounts of centrifuging waste of mineral wool melt (CMWW) are created during the production of mineral wool. CMWW is technogenic aluminum silicate raw material, formed from the particles of undefibred melt (60–70%) and mineral wool fibers (30–40%). 0.3–0.6% of organic binder with phenol and formaldehyde in its composition exists in this material. Objective of the research is to investigate the possibility to use CMWW as an additive for the production of ceramic products, by neutralising phenol and formaldehyde existing in CMWW. Formation masses were prepared by incorporating 10%, 20% and 30% of CMWW additive and burned at various temperatures. It was identified that the amount of 10–30% of CMWW additive influences the following physical and mechanical properties of the ceramic body: lowers drying and firing shrinkage, density, increases compressive strength and water absorption. Investigations carried out show that CMWW waste can be used for the production of ceramic products of various purposes.

View all citing articles on Scopus

View full text

Correlation between P3HT inter-chain structure and Jsc of P3HT:PC[70]BM blends for solar cells

Abstract

Graphical abstract

Highlights

Introduction

Section snippets

Experimental

Results and discussion

Conclusions

Acknowledgements

Sol Energy Mater Sol Cells

Sol Energy Mater Sol Cells

Org Electron

Microelectron Reliab

Sol Energy Mater Sol Cells

Advance materials and processes for polymer solar cell devices

J Mater Chem

Polymer photovoltaic cells: enhanced efficiencies via a network of internal donor–acceptor heterojunctions

Science

Solar cell efficiency table (version 39)

Res Appl

Plastic solar cells: self-assembly of bulk heterojunction nano-materials by spontaneous phase separation

Acc Chem Res

Design rules for donors in bulk heterojunction solar cells: towards 10% energy conversion efficiency

Adv Mater

2.5% efficient organic plastic solar cells

J Appl Phys

Correlation between P3HT inter-chain structure and J_sc of P3HT:PC_[70]BM blends for solar cells