Efficient Organic Photovoltaic Devices Research Articles

Secondary Aggregation Induced by Volatile Additive for Improved Exciton Diffusion and Charge Separation in High Efficiency Organic Photovoltaic Devices

Secondary Aggregation Induced by Volatile Additive for Improved Exciton Diffusion and Charge Separation in High Efficiency Organic Photovoltaic Devices

Dilute Donor Organic Solar Cells Based on Non-fullerene Acceptors.

The advent of small molecule non-fullerene acceptor (NFA) materials for organic photovoltaic (OPV) devices has led to a series of breakthroughs in performance and device lifetime. The most efficient OPV devices have a combination of electron donor and acceptor materials that constitute the light absorbing layer in a bulk heterojunction (BHJ) structure. For many BHJ-based devices reported to date, the weight ratio of donor to acceptor is near equal. However, the morphology of such films can be difficult to reproduce and manufacture at scale. There would be an advantage in developing a light harvesting layer for efficient OPV devices that contains only a small amount of either the donor or acceptor. In this work we explore low donor content OPV devices composed of the polymeric donor PM6 blended with high performance NFA materials, Y6 or ITIC-4F. We found that even when the donor:acceptor weight ratio was only 1:10, the OPV devices still have good photoconversion efficiencies of around 6% and 5% for Y6 and ITIC-4F, respectively. It was found that neither charge mobility nor recombination rates had a strong effect on the efficiency of the devices. Rather, the overall efficiency was strongly related to the film absorption coefficient and maintaining adequate interfacial surface area between donor and acceptor molecules/phases for efficient exciton dissociation.

Invariant Charge Carrier Dynamics Using a Non-Planar Non-Fullerene Acceptor across Multiple Processing Solvents.

Conventional non-fullerene acceptors (NFAs) typically have planar structures that can enable improved electron mobility and produce more efficient organic photovoltaic devices. A relatively simple A-D-A'-D-A type NFA specifically designed to match with poly(3-hexylthiophene-2,5-diyl) (P3HT) for green-absorbing agrivoltaic applications has been examined using a variety of techniques: microsecond transient absorption spectroscopy, atomic force microscopy, and photoluminescence. Relatively invariant charge carrier decay dynamics are observed in the blend films across a variety of processing solvents. Raman spectroscopy in conjunction with computational studies reveals that this NFA is non-planar and that multiple conformations are present in films, while preserving the crystalline nature of P3HT. The non-planarity of the NFA therefore creates a dispersive acceptor environment, irrespective of processing solvent, and this leads to the observed relative invariance in charge carrier decay dynamics and high tolerance to morphological variation. The findings presented in this work highlight the potential of non-planar materials as acceptors in organic photovoltaic devices.

Enhancing the indoor performance of organic photovoltaic devices: interface engineering with an aminobenzoic-acid-based self-assembled monolayer

Significant advances in the performance of organic photovoltaic (OPV) devices can facilitate their use in internet of things applications. However, achieving excellent photostability and high efficiency using stable, efficient OPV devices in indoor settings is considerably difficult. To address this issue, a zinc oxide (ZnO) electron transport layer (ETL) was modified with a self-assembled monolayer of 4-aminobenzoic acid (ABA) in the present study, and the impact of this modification was correlated with the indoor performance of an OPV device with the PM6:L8-BO photoactive layer. The ABA-treated ZnO ETL exhibited a significant reduction in the work function (from 4.51 to 4.04 eV), surface roughness (from 0.201 to 0.177 nm), and hydrophilicity of an indium-tin-oxide electrode; this aided in selectively extracting charge carriers from the device and minimizing trap-assisted recombination losses. Additionally, the ABA treatment of the ZnO ETL considerably enhanced the electron mobility and recombination resistance. It reduced the trap density, thereby enabling the ZnO/ABA-based device to achieve improved performance. Consequently, the ZnO/ABA-based device exhibited a noteworthy 14.68% higher maximum power output than that of the device without any ZnO surface modification under 1000 lx halogen (HLG) illumination (P out, max = 354.48 and 309 µA cm−2, respectively). Moreover, under thermal illumination conditions (1000 lx HLG lighting), the ZnO/ABA-based device sustained ∼74% of its initial power conversion efficiency over 120 h, significantly higher than its ABA-free equivalent (∼55%).

THE OPTIMIZATION OF P3HT:PCBM THIN FILM THICKNESS FOR ORGANIC SOLAR CELLS

This study presents the complex relationship between film thickness and the properties of P3HT:PCBM thin films, looking at how different thicknesses affected their structural and optical properties. Poly(3, hexylthiophene) (P3HT) and poly(3, hexylthiophene) (PCMB) were blended in a 0.6:1 ratio and deposited using spin coating techniques. The research involve investigating the resulting changes in surface topography, optical properties, and electrical behaviour by systematically adjusting the film thickness through multiple coating repetitions ranging from one to three repetitions. Profilometric analysis revealed a direct relationship between film thickness and surface roughness, highlighting the importance of thickness in interfacial interactions within solar cells. Optical studies revealed fascinating trends in absorbance, transmittance, absorption coefficient, and extinction coefficient, highlighting the films' behaviour at various wavelengths. Surprisingly, regardless of thickness, the optical band gap remained constant, providing valuable insights for optimizing photon energy conversion. Measurements of the Hall effect revealed the effect of thickness on carrier mobility, concentration, conductivity, resistivity, and Hall voltage. Thinner films had higher mobility but lower carrier concentration, revealing a delicate balance critical for optimizing charge transport. The comprehensive analysis of the study sheds light on the complex interplay between film thickness and various properties, providing useful guidance for designing efficient P3HT:PCBM organic solar cells. This study's findings highlight the importance of precise control over film dimensions in improving the performance and efficiency of organic photovoltaic devices. This investigation paves the way for tailored approaches in the fabrication of next-generation organic solar cells, pushing the limits of renewable energy technology.

Scalable and sustainable manufacturing of ultrathin metal–organic framework nanosheets (MONs) for solar cell applications

Metal-organic framework nanosheets (MONs) are an emerging class of 2D materials whose tunable chemistry make them ideal for a wide range of sensing, catalytic, electronics and separation applications. However, creating scalable routes to the synthesis of high quality, ultrathin nanosheets remains challenging and little consideration has been given to the economics of making these materials. Here, we demonstrate a scalable synthesis of zinc-porphyrin based nanosheets, Zn2(H2TCPP), for use in organic solar cells and conduct a techno-economic analysis of their pilot-plant scale manufacture. A thorough investigation of the process chemistry of the solvothermal synthesis enabled reduction of reaction time, increased solid content and scale-up of the reaction in batch. Significantly, the addition of triethylamine accelerated the reaction kinetics, which enabled the synthesis temperature to be dropped from > 80 °C to room temperature. Application of these new reaction conditions in a continuous stirred-tank reactor directly formed monolayer MONs at 99 % yield with a space–time yield of 16 kg m−3 day−1, an approximately 20-fold increase in yield compared to adapting the literature procedure. Techno-economic analysis showed a 94 % reduction in the production costs compared to the literature reaction conditions and indicated that the production cost was dominated by ligand price. The general applicability of the method was demonstrated through synthesis of related Cu2(H2TCPP) MONs and tunability through metalation of the porphyrin units with six different metal ions. Finally, the value of the nanosheets was demonstrated through a near doubling in the power conversion efficiency of organic photovoltaic devices when the MONs were incorporated into the active layer. Overall, this work demonstrates the first scalable and sustainable route to producing monolayer nanosheets for high value applications.

Work function tuning of directly grown graphene via ultraviolet–ozone treatment for electrode application in organic photovoltaic devices

Graphene is an efficient electrode material for flexible optoelectronic devices because of its high transmittance and electrical conductivity. A graphene film directly grown using plasma-enhanced chemical vapor deposition is suitable for electrode applications because it can be prepared on a glass substrate at relatively low temperatures without a transfer process from a metal catalyst. However, to obtain efficient optoelectronic devices using graphene electrodes, surface modification is necessary. Herein, we tuned the work function of a graphene electrode using ultraviolet (UV)-O3 treatment. The power conversion efficiency of organic photovoltaic devices was significantly increased by the UV-O3 treatment of the graphene anode. To investigate the origin of the improved device performance, the interface between the graphene anode and tetraphenyldibenzoperiflanthene (DBP) donor layer was analyzed via in situ ultraviolet photoelectron spectroscopy. The energy offset between the Fermi level of graphene and the highest occupied molecular orbital level of DBP was significantly reduced because of the increased work function. The results indicate that the electronic structure modification of graphene is of significant importance for fabricating efficient optoelectronic devices.

Toward High Efficiency Water Processed Organic Photovoltaics: Controlling the Nanoparticle Morphology with Surface Energies

AbstractHere efficient organic photovoltaic devices fabricated from water‐based colloidal dispersions with donor:acceptor composite nanoparticles achieving up to 9.98% power conversion efficiency (PCE) are reported. This high efficiency for water processed organic solar cells is attributed to morphology control by surface energy matching between the donor and the acceptor materials. Indeed, due to a low interfacial energy between donor and the acceptor, no large phase separation occurs during the nanoparticle formation process as well as upon thermal annealing. Indeed, synchrotron‐based scanning transmission X‐ray microscopy reveals that the internal morphology of composite nanoparticles is intermixed as well as the active layer morphology after thermal treatment. The PCE of this system reaches 85% that of devices prepared from chlorinated solvent. The gap between water‐based inks and organic solvent‐based inks gets narrower, which is promising for the development of eco‐friendly processing and fabrication of organic photovoltaics.

The complex permittivity of PEDOT:PSS.

High permittivity materials are required for efficient organic photovoltaic devices, and the addition of the conjugated polymer composite poly(3,4-ethylenedioxythiophen) polystyrene sulfonate (PEDOT:PSS) to dielectric polymers has been shown to significantly heighten their permittivity. The permittivity of PEDOT:PSS at the optical and microwave frequencies has been investigated, but PEDOT:PSS layers are mainly used for low-frequency device applications, where accurate dielectric property measurements are hindered by their high electrical conductivity and the problems arising from the metal-polymer interfaces. Here, we determine the complex relative permittivity (εr*=εr'-jεr″) of PEDOT:PSS layers perpendicular to the layer plane in the 10-2-106 Hz range by combining data from the reactive energy estimations and electrochemical impedance spectroscopy, and discover that: εr' at <1Hz is ultra-high (∼106) decreasing with frequency to ∼5 at 106 Hz; the experimental data fit the Cole-Cole dielectric relaxation model by considering multiple relaxation mechanisms; PEDOT:PSS polarizes nonlinearly and εr' increases with the intensity of the applied external field; low frequency εr' increases with both thickness and temperature of the layer, opposite trend of temperature-dependence prevails at >103Hz; the dielectric properties of PEDOT:PSS are highly anisotropic and the in-plane εr' at 1.0kHz is three orders of magnitude higher than the vertical εr'; and that the εr'' decreases proportional to the reciprocal of frequency (1/f). The latter finding provides an explanation for the ubiquitous pink noise accompanying signals transmitted through organic conductor links. The described methodology can be adopted for investigations on other conjugated polymers.

Unveiling the Morphological and Physical Mechanism of Burn-in Loss Alleviation by Ternary Matrix Toward Stable and Efficient All-Polymer Solar Cells.

All-polymer solar cells (All-PSCs) are considered the most promising candidate in achieving both efficient and stable organic photovoltaic devices, yet the field has rarely presented an in-depth understanding of corresponding device stability while efficiency is continuously boosted via the innovation of polymer acceptors. Herein, a ternary matrix is built for all-PSCs with optimized morphology, improved film ductility and importantly, boosted efficiency and better operational stability than its parental binary counterparts, as a platform to study the underlying mechanism. The target system PQM-Cl:PTQ10:PY-IT (0.8:0.2:1.2) exhibits an alleviated burn-in loss of morphology and efficiency under light soaking, which supports its promoted device lifetime. The comprehensive characterizations of fresh and light-soaked active layers lead to a clear illustration of opposite morphological and physical degradation direction of PQM-Cl and PTQ10, thus resulting in a delicate balance at the optimal ternary system. Specifically, the enlarging tendency of PQM-Cl and shrinking preference of PTQ10 in terms of phase separation leads to a stable morphology in their mixing phase; the hole transfer kinetics of PQM-Cl:PY-IT host is stabilized by incorporating PTQ10. This work succeeds in reaching a deep insight into all-PSC's stability promotion by a rational ternary design, which booms the prospect of gaining high-performance all-PSCs.

Study on Optical Efficiency of Organic Photovoltaic Devices with Multi-Tip Metal Nanostructures

As a new generation of photovoltaic devices, organic polymer solar cell (Organic Solar Cell, OSC) have attracted wide attention of researchers in recent years because of their unique advantages such as simple process, low energy consumption, low cost and large area preparation. However, the development of OSC has encountered bottlenecks: the low carrier mobility of photovoltaic materials forces the thickness of the active layer of OSC to be reduced as much as possible to meet the requirements of effective collection of photogenerated carriers, while the thinner absorption layer will lead to serious optical absorption loss and device performance degradation. Therefore, how to enhance the optical absorptivity of OSC on the premise of effective carrier collection has become a research hot-spot. Based on this characteristic, with the help of finite element method, the structure model of OSC with multi-tip metal nanoparticles is established, and the effects of metal nanospheres and star particles on OSC light absorption factors are studied systematically. Firstly, the effects of introducing metal nanoparticles into different functional layers of OSC (active layer and buffer layer) are compared and analyzed to determine the introduction location of metal nanoparticles in OSC. Secondly, the localized resonance enhancement rules of spherical and cubic metal nanoparticles in the functional layer are discussed. Combined with the theoretical model, the optimal design method of metal nanoparticles structure parameters (size and period) is established. The results show that the absorption enhancement of metal nanoparticles in the active layer of OSC is higher than that in the buffer layer. On the one hand, it can stimulate more electron hole pair separation, improve the separation rate of electron hole pair, on the other hand, it can also make the separated electron hole to obtain more energy, recombination becomes relatively difficult, and the arrival rate of the battery electrode is improved.

An n‐n Heterojunction Configuration for Efficient Electron Transport in Organic Photovoltaic Devices

AbstractSelective electron transport and extraction are essential to the operation of photovoltaic devices. Electron transport layer (ETL) is therefore critical to organic photovoltaics (OPV). Herein, an ETL configuration is presented comprising a solution‐processed n‐n organic heterojunction to enhance electron transport and hole blocking, and boost power conversion efficiency (PCE) in OPV. Specifically, the n‐n heterojunction is constructed by stacking a narrow‐band n‐type conjugated polymer layer (PNDIT‐F3N) and a wide‐band n‐type conjugated molecule layer (Phen‐NaDPO). Based on the ultraviolet photoelectron spectroscopy measurement and numerical simulation of current density‐voltage characteristics, the formation of the built‐in potential is investigated. In three OPVs with different active layers, substantial improvements are observed in performance following the introduction of this ETL configuration. The performance enhancement arises from the combination of selective carrier transport properties and reduced recombination. Another contributing factor is the good film‐forming quality of the new ETL configuration, where the surface energies of the related materials are well‐matched. The n‐n organic heterojunction represents a viable and promising ETL construction strategy for efficient OPV devices.

Designing the optoelectronic properties of BODIPY and their photovoltaic applications for high performance of organic solar cells by using computational approach

A series of four novel pi-conjugated chromophores named BDP1-BDP4 have been designed in quest to enhance the PCE of organic photovoltaic cells. These chromophores were developed by using 4,4-difluroboradiaza-s-indacene (BODIPY) as a core, Triphenylamine (TPA) as donor and different end-capped acceptors i.e., 2-ethylidene malononitrile (BDP1), methyl-2-cyanobut-2-enoate (BDP2), 4-ethylidene-2-methyl-5-thiooxoisothiazolidin-3-one (BDP3), 2-(2-ethylidene-5,6-difluoro-3-oxo-2,3-dihydroinden-1-ylidene) malononitrile (BDP4). DFT and TD-DFT approach using B3LYP functional was employed to assess the photophysical, as well as opto-electronic properties of designed chromophores BDP1-BDP4. FMOs and Transition Density Matrix evaluations were executed to get insights about charge distribution, chemical reactivity, and stability of all molecules under investigation. Exciton binding energy and reorganization energy values have been computed to investigate exciton dissociation and charge carrier mobilities, respectively. All the newly developed molecules exhibit reduced band gap, red shift absorption bands, low exciton binding energy, small reorganization energy values and moderate Voc value in comparison to reference molecule which demonstrate that these newly developed molecules can be utilized as favorable photovoltaic materials. BDP4 considered to be promising acceptor molecule with highest λmax (883 nm), narrow band gap (1.22eV) and lowest λe value (0.01136). This theoretical and computational study revealed that the designed chromophores could be employed as efficient acceptors, in order to upsurge the quantum efficiency of organic photovoltaic devices.

Improved hole injection/extraction using PEDOT:PSS interlayer coated onto high temperature annealed ITO electrode for efficient device performances

We demonstrate the improved device performances by using the structure of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film coated onto the indium tin oxide (ITO) anodic electrode annealed at 400 °C under the normal ambient. The ITO thin films show the improved film quality with decreased dislocation density and lattice strain as annealing temperature increases. The spin-coated PEDOT:PSS film smoothens the wrinkle kind of surface morphology of the ITO film annealed at 400 °C. The annealed ITO (400 °C) with PEDOT:PSS interlayer improves the hole-current density in the hole-only devices (HODs) having the device structure of ITO/PEDOT:PSS/N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine as hole-transporting layer/Al. It enhances the efficiency of organic photovoltaic devices [ITO (annealed)/PEDOT:PSS/P3HT:PCBM (active layer)/LiF/Al] by three times higher (1.69 %) when compared to that (0.48 %) of pristine ITO based OPV device. These results show that the annealing of ITO film at the high temperature of 400 °C under the normal ambient improves the film quality and lowers the potential energy barrier at ITO/PEDOT:PSS interface for effective hole injection/extraction process, resulting in the enhanced device electrical performances. • Annealed ITO films improve film quality with decreased dislocation density and lattice strain. • PEDOT:PSS smoothens the wrinkle kind of surface morphology of ITO annealed at 400 °C. • 400 °C annealed ITO with PEDOT:PSS interlayer lowers the potential barrier and improves hole-current density in HODs. • It enhances the efficiency of OPVs by three times (1.69%) compared to that (0.48%) of pristine ITO based OPV. • 400 °C annealed ITO film lowers potential barrier at ITO/PEDOT:PSS interface for effective hole injection/extraction process.

Direct Quantification of Quasi-Fermi-Level Splitting in Organic Semiconductor Devices

Non-radiative losses to the open-circuit voltage are a primary factor in limiting the power conversion efficiency of organic photovoltaic devices. The dominant non-radiative loss is intrinsic to the active layer and can be determined from the quasi-Fermi level splitting (QFLS) and the radiative thermodynamic limit of the photovoltage. Quantification of the QFLS in thin film devices with low mobility is challenging due to the excitonic nature of photoexcitation and additional sources of nonradiative loss associated with the device structure. This work outlines an experimental approach based on electro-modulated photoluminescence, which can be used to directly measure the intrinsic non-radiative loss to the open-circuit voltage; thereby, quantifying the QFLS. Drift-diffusion simulations are carried out to show that this method accurately predicts the QFLS in the bulk of the device regardless of device-related non-radiative losses. State-of-the-art PM6:Y6-based organic solar cells are used as a model to test the experimental approach, and the QFLS is quantified and shown to be independent of device architecture. This work provides a method to quantify the QFLS of organic solar cells under operational conditions, fully characterizing the different contributions to the non-radiative losses of the open-circuit voltage. The reported method will be useful in not only characterizing and understanding losses in organic solar cells, but also other device platforms such as light-emitting diodes and photodetectors.

Over 17.6% Efficiency Organic Photovoltaic Devices with Two Compatible Polymer Donors

Efficient ternary blend organic photovoltaic devices (OPVs) are built based on a D18‐Cl:Y6 host system and star polymer donor PM6 as the third component. A power conversion efficiency (PCE) of 16.89% is achieved in D18‐Cl:Y6 host binary OPVs, with a short‐circuit current density (J SC) of 25.31 mA cm−2, an open‐circuit voltage (V OC) of 0.878 V, and a fill factor (FF) of 75.81%. Upon incorporating appropriate PM6 in active layers, the PCE of optimal ternary blend OPVs can be increased to 17.61%, benefiting from a J SC of 26.35 mA cm−2, a V OC of 0.871 V, and an FF of 76.82%. Polymers D18‐Cl and PM6 have good compatibility and similar highest occupied molecular orbital (HOMO) levels, which enable to form D18‐Cl:PM6 alloyed states for efficient hole transport in ternary blend active layers. Meanwhile, trap density in ternary blend active layers is decreased by incorporating PM6, which is conducive to weaken charge recombination in ternary blend active layers. The gradually varied V OC values of ternary blend OPVs can be well explained from the varied HOMO levels of D18‐Cl:PM6 alloyed states. The results indicate that two compatible polymer donors with similar HOMO levels have great potential in achieving efficient ternary blend OPVs.

Transparent Conducting Electrodes for Efficient Organic Photovoltaic Devices under Indoor Light Conditions: A Brief Review

Transparent Conducting Electrodes for Efficient Organic Photovoltaic Devices under Indoor Light Conditions: A Brief Review

Electronic properties of donor:acceptor complexes in all-polymer solar cells based on density functional theory

The electronic properties at the donor (D):acceptor (A) interface are a crucial factor in determining the efficiency of organic photovoltaic devices. Here, based on first-principles calculations, the electronic properties of ten configuration complexes composed of D polymer PDPPTPT and A polymer PNDI2OD-TVT were simulated. Results show that the bandgap values of the homo-/heterojunctions decrease with the increase of the number of molecular layers, and that of AAA is close to zero. This indicates that the homogeneous stacking is favorable for charge transport; furthermore, the bandgap of the complexes is affected by the molecular arrangement. Through the differential charge density and Bader charge analysis method, it was found that charge transfer will occur intermolecularly, which promotes the formation of a dipole moment at the D:A interface, and the dipole electric field then helps the dissociation of excitons in the active layer. The amount of charge transfer at the D:A interface in the DDA, DAA and DDAA configurations is about twice that in the DA configuration alone, demonstrating that homogeneous accumulation in complexes can enhance the interface dipole interaction. The comprehensive analysis suggests that homogeneous accumulation is conducive to charge transport, that heterogeneous stacking helps to promote exciton dissociation, and that there should be an optimal ratio. Furthermore, the dipole electric fields formed at the D:A interface exhibit the characteristics of local and non-uniform distribution.

Aggregation Controlled Charge Generation in Fullerene Based Bulk Heterojunction Polymer Solar Cells: Effect of Additive

Optimization of charge generation in polymer blends is crucial for the fabrication of highly efficient polymer solar cells. While the impacts of the polymer chemical structure, energy alignment, and interface on charge generation have been well studied, not much is known about the impact of polymer aggregation on charge generation. Here, we studied the impact of aggregation on charge generation using transient absorption spectroscopy, neutron scattering, and atomic force microscopy. Our measurements indicate that the 1,8-diiodooctane additive can change the aggregation behavior of poly(benzodithiophene-alt-dithienyl difluorobenzotriazole (PBnDT-FTAZ) and phenyl-C61-butyric acid methyl ester (PCBM)polymer blends and impact the charge generation process. Our observations show that the charge generation can be optimized by tuning the aggregation in polymer blends, which can be beneficial for the design of highly efficient fullerene-based organic photovoltaic devices.

Driving Force for Exciton Dissociation in Organic Solar Cells: The Influence of Donor and Acceptor Relative Orientation

The presence of a favorable driving force for electron transfer (ΔG) at the donor/acceptor (D/A) interface is fundamental to overcome the exciton binding energy and improve the efficiency of organic photovoltaic devices (OPVs). Using density functional theory (DFT), time-dependent DFT, and classical molecular dynamics, here we systematically investigate the dependence of ΔG on the molecular orientation between the donor and the acceptor in the dimer. This study was performed by considering the model configuration of D/A species of four donor A–D–A molecules named DRCN­(4–7)­T and C60 acceptor. We identified two configurations that gave the highest negative values of ΔG (which favors exciton dissociation): (i) face-on orientation when the fullerene is located at the central thiophene ring of the DRCN­(4–7)­T molecule. In this situation, the high degree of hybridization between the highest occupied molecular orbital of the acceptor and the lowest unoccupied molecular orbital of the donor stabilizes the energy of the lowest charge transfer state (CT1). (ii) Edge-on orientation when C60 is close to the positive partial charges of the D molecule. In this configuration, the fullerene further polarizes the D molecule which enhances the dimers’ dipole moment. The electrostatic potential produced by this dipole decreases then the energy of the CT1 state. Molecular dynamics calculations performed to simulate the deposition of DRCN5T/C60 blends showed that dimers with a very negative driving force (as identified by our DFT calculations) are indeed present in the film. We also found a tweezers-like effect produced by the lateral alkyl groups attached to the central thiophene ring of the DRCN5T molecule. Those lateral groups can capture the fullerenes and guide them toward the center of the molecule during the solvent evaporation. This process would favor the formation of face-on dimers that tend to have a negative ΔG. The comparison of our data with experimental results measured in DRCN­(4–7)­T suggests that there is a correlation between negative values of ΔG (averaged over some D/A configurations) and the performance of the corresponding solar cell. The fine-tuning of the D/A configuration can make the difference to decrease the germinated recombination and improve the efficiency of OPVs.