Performance Of Polymer Solar Cells Research Articles

An alcohol-soluble small molecule as efficient cathode interfacial layer materials for polymer solar cells

Abstract Interface modification makes an important contribution to improving the optoelectronic performance and stability of polymer solar cells (PSCs). Here, the hexamethylenetetramine (C6H12N4) was successfully introduced into PSCs as cathode interface layers (CILs) using environmental-friendly methanol as solvent. Compared to the PSCs without CILs, the open circuit voltage (VOC) and short-circuit current density (JSC) of the device with C6H12N4 CILs was increased from 0.44 V to 12.73 mA cm−2 to 0.77 V and 15.89 mA cm−2, respectively. More importantly, under the same experimental conditions, the optimal power conversion efficiency (PCE) of the device with C6H12N4 CILs was improved to 7.79%, which is 185% higher than that of the device without C6H12N4 CILs (2.73%). We found that the active layer PTB7-Th:PC71BM showed a smoother interface morphology and better hydrophilicity after insertion of CILs, which facilitated enhance the physical contact between active layers and cathode as well as electron extraction and transport. The results show that the introduction of C6H12N4 as CILs provides an effective method for preparing high-performance PSCs.

Difluoroterthiophene as promising block to build highly planar conjugated polymer for polymer photovoltaic cells

Developing highly planar semiconducting polymer is essential for achieving high mobility and improving the photovoltaic performance of bulk-heterojunction polymer solar cells. In this contribution, two novel low-bandgap donor-acceptor copolymers, P1-3T and P2-3T2F, consisting of electron-accepting benzothiadiazole acceptor segment and electron-donating terthiophene donor segment with and without fluorine atoms were designed and synthesized. The density functional theory calculations and ultraviolet–visible absorption studies demonstrate that the fluorinated P2-3T2F polymer has more planar backbone conformation, deeper HOMO level, broader absorption spectrum with a vibronic shoulder peak, and higher absorption coefficient compared with the non-fluorinated analogue polymer, P1-3T. Furthermore, P2-3T2F exhibits good crystallinity and high hole mobility, presumably due to the well-ordered lamellar packing and the π-π stacking interaction between the backbones of the conjugated polymers. The optimized polymer solar cell based on P2-3T2F:PC61BM exhibits a short-circuit current density (Jsc) of 12.77 mA cm−2, a fill factor (FF) of 68.99%, an open-circuit voltage (Voc) of 0.80 V, and a maximum power conversion efficiency (PCE) of 7.14%, which is approximately 46% higher than that of the P1-3T:PC61BM device. The enhanced PCE is primarily due to increased light-harvesting ability and interconnected morphology with finely dispersed polymer-rich and PC61BM-rich domains, which improves the efficiency of exciton dissociation and rises the mobility of charge carriers, thus boosting the short-circuit current density and the FF value. Moreover, the relatively deep HOMO of P2-3T2F effectively increases the Voc.

Synthesis, characterization, and optoelectronic properties of phenothiazine-based organic co-poly-ynes

We present the synthesis of seven new organic co-poly-ynes P1–P7 incorporating phenothiazine (PTZ) motif and evaluate their optoelectronic properties and performance in polymer light-emitting diodes (PLEDs) and polymer solar cells (PSCs).

17.1 %‐Efficient Eco‐Compatible Organic Solar Cells from a Dissymmetric 3D Network Acceptor

AbstractTo elevate the performance of polymer solar cells (PSC) processed by non‐halogenated solvents, a dissymmetric fused‐ring acceptor BTIC‐2Cl‐γCF3 with chlorine and trifluoromethyl end groups has been designed and synthesized. X‐ray crystallographic data suggests that BTIC‐2Cl‐γCF3 has a 3D network packing structure as a result of H‐ and J‐aggregations between adjacent molecules, which will strengthen its charge transport as an acceptor material. When PBDB‐TF was used as a donor, the toluene‐processed binary device realized a high power conversion efficiency (PCE) of 16.31 %, which improved to 17.12 % when PC71ThBM was added as the third component. Its efficiency of over 17 % is currently the highest among polymer solar cells processed by non‐halogenated solvents. Compared to its symmetric counterparts BTIC‐4Cl and BTIC‐CF3‐γ, the dissymmetric BTIC‐2Cl‐γCF3 integrates their merits, and has optimized the molecular aggregations with excellent storage and photo‐stability, and also extending the maximum absorption peak in film to 852 nm. The devices exhibit good transparency indicating a potential utilization in semi‐transparent building integrated photovoltaics (ST‐BIPV).

17.1 %-Efficient Eco-Compatible Organic Solar Cells from a Dissymmetric 3D Network Acceptor.

To elevate the performance of polymer solar cells (PSC) processed by non-halogenated solvents, a dissymmetric fused-ring acceptor BTIC-2Cl-γCF3 with chlorine and trifluoromethyl end groups has been designed and synthesized. X-ray crystallographic data suggests that BTIC-2Cl-γCF3 has a 3D network packing structure as a result of H- and J-aggregations between adjacent molecules, which will strengthen its charge transport as an acceptor material. When PBDB-TF was used as a donor, the toluene-processed binary device realized a high power conversion efficiency (PCE) of 16.31 %, which improved to 17.12 % when PC71ThBM was added as the third component. Its efficiency of over 17 % is currently the highest among polymer solar cells processed by non-halogenated solvents. Compared to its symmetric counterparts BTIC-4Cl and BTIC-CF3 -γ, the dissymmetric BTIC-2Cl-γCF3 integrates their merits, and has optimized the molecular aggregations with excellent storage and photo-stability, and also extending the maximum absorption peak in film to 852 nm. The devices exhibit good transparency indicating a potential utilization in semi-transparent building integrated photovoltaics (ST-BIPV).

Interface engineering of electrochemically deposited ZnO nanorods as electron transport layer in polymer solar cells using organic dyes

The electron transporting layer (ETL) plays a vital role on determining the charge extraction, charge transfer and consequently the photovoltaic performance of polymer solar cells (PSCs). Methylene Blue (MB) and Rhodamine 6G (Rh6G) were applied as modifying agents to reduce the inherent incompatibility between the ZnO NRDs and the P3HT:PCBM based active layer. ZnO NRDs were electrochemically grown on the seed layer-coated ITO electrode using a constant potential and they were modified with MB and Rh6G dyes by a dip-coting method. The optical properties, structural defects and morphology of the unmodified and dye-modified ZnO NRDs were compared. The rate of charge recombination and electron transfer as the most important factors influencing the photovoltaic performance of PSCs was evaluated using different techniques including PL-decay, EIS and AFM. Rh6G appeared to act as a more appropriate modifying agent, due to its larger π-conjugated network, which was beneficial to the charge transfer at the interfaces and decreasing the energy loss within the fabricated PSCs. The surface morphology of the P3HT:PCBM thin film layer appeared to be smoother in the Rh6G-modified samples. The highest charge mobility of 4.56 × 10−4 cm2/V was observed for the Rh6G-modified devices, which was about 120% and 54% higher than that obtained for the unmodified and MB-modified samples, respectively. The fabricated MB-and Rh6G-modified devices illustrated PCE of 3.65 and 5.1%, respectively, which were considerably higher than that achieved with the unmodified ZnO NRDs based devices prepared in the current work and reported previously.

Optimizing polymer aggregation and blend morphology for boosting the photovoltaic performance of polymer solar cells via a random terpolymerization strategy

Two random terpolymers were designed and synthesized to systematically study their photovoltaic performances. The PBNB80 -based device shows an outstanding PCE of 16.0%, which is much higher than those of their binary parent polymers. Compared to regular conjugated polymers, the random conjugated terpolymers are usually not beneficial to achieve highly efficient non-fullerene (NF)-based polymer solar cells (PSCs) due to their disordered chemical structures. In this work, we report two random terpolymer donors ( PBNB80 and PBNB50 ) by tuning the molar ratio of electron-accepting units of 1,3-di(thiophen-2-yl)naphtho[2,3-c]thiophene-4,9-dione (NTD) and 1,3-bis(4-chlorothiophen-2-yl)-4H,8H-benzo[1,2-c:4,5-c']dithiophene-4,8-dione (Cl-BDD), at the same time, the parent polymers ( PBNB100 and PBNB00 ) are also compared to study. These four polymer donors exhibit similar optical bandgaps and gradually deepen highest occupied molecular orbital levels. Importantly, aggregation and self-organization properties of the random terpolymer donors are optimized, which result in the better morphology and crystal coherence length after blending with NF acceptor of BO-4Cl. Particularly, a PBNB80 :BO-4Cl blend forms an optimal nanoscale phase-separation morphology, thereby producing an outstanding power conversion efficiency of 16.0%, which is much higher than those (12.8% and 10.7%) of their parent binary polymer donor-based devices. This work demonstrates that rational using terpolymerization strategy to prepare random terpolymer is a very important method to achieve highly efficient NF-PSCs.

Wide bandgap donor polymers containing carbonyl groups for efficient non-fullerene polymer solar cells

Two wide bandgap conjugated polymers (PTCO8 and PTCO1) with different side chains, composed of alkylcarbonyl-substituted thiophene (TOC) as the electron-withdrawing unit and two-dimension benzodithiophene (BDT) as the electron-donating unit, are developed for non-fullerene polymer solar cells (PSCs). Relative to non-carbonyl-substituted control polymer PTC8, PTCO8 and PTCO1 exhibit a red-shifted absorption and deeper-lying highest occupied molecular orbital (HOMO) level. When blended with ITIC, the as-cast PTCO1-based devices yield a power conversion efficiency of up to 9.33% with an open-circuit voltage of 0.95 V, a short-circuit current density of 16.91 mA cm−2, and a fill factor of 57.9%, outperforming those of PTC8-based devices (4.04%) and PTCO8-based devices (5.91%). This work demonstrates that the carbonyl group is a promising electron-deficient moiety to construct wide-bandgap polymers for non-fullerene PSCs. Adjusting the length of side chains is a feasible strategy to improve PSC performance further.

Highly efficient polymer solar cells with improved molecular stacking and appropriate active layer morphology by side chain engineering of small molecular acceptors

For indacenodithiophene (IDT) core-based small molecule acceptors (SMAs), side chains attached onto the sp3 carbon of the IDT unit can not only improve the film-forming characteristics of SMAs, but also adjust the molecular stacking, optical properties, and morphology of the active layer of polymer solar cells (PSCs). In this paper, we obtained an efficient IDT core-based SMA C4Ph-IDT-DFIC with a phenyl at the tail of alkyl side chain. Compared with IDIC-4 F with the phenyl group inside the alkyl chain, the C4Ph-IDT-DFIC exhibited different absorption spectras, energy levels, molecular stacking and morphological properties when blended with donor material PM6. And the C4Ph-IDT-DFIC showed a wider absorption range in the 500–806 nm with lower optical band gap of 1.54 eV (~40 nm red-shifted than IDIC-4 F), due to the improved molecular stacking. Moreover, PM6:C4Ph-IDT-DFIC devices showed higher and more balanced charge mobilities. PSCs based on PM6:C4Ph-IDT-DFIC exhibited a power conversion efficiency (PCE) of 10.47% with a short-circuit current (Jsc) of 17.78 mA cm−2, while the PM6:IDIC-4 F device yielded a PCE of 9.26% with a Jsc of 15.18 mA cm−2. Our work provides a feasible molecular design strategy to adjust the molecular stacking and improve photovoltaic performance of PSCs.

Zinc Oxide Coated Carbon Dot Nanoparticles as Electron Transport Layer for Inverted Polymer Solar Cells

Interface engineering is a powerful tool to improve the performance of polymer solar cells (PSCs), and zinc oxide (ZnO) is a significant interfacial material for PSCs. However, ZnO is easy to agglo...

Naphtho[2,3-c]thiophene-4,9-dione based polymers for efficient fullerene solar cells

Designing and synthesizing new organic photovoltaic materials is an inexhaustible driving force for the development of polymer solar cells (PSCs). For an excellent molecular structure with a certain conjugated skeleton, studying its analogues is of considerable significance for fully exploiting its photovoltaic potential. In this work, naphtho[2,3-c]thiophene-4,9-dione (NTD), an analogue of benzo [1,2-c:4,5-c’]dithiophene-4,8-dione (BDD), was designed and synthesized. Based on this building block, alkoxy side chains and alkylthio side chains were grafted on NTD to build NTD-O and NTD-S unit respectively, and then two new D-A conjugated donor polymers, PBNO and PBNS, were synthesized with NTD-O and NTD-S units as acceptor units and asymmetric benzodithiophene unit (asy-BDTBP) as donor units. Later, the photoelectric properties of these two materials in fullerene PSCs were studied. Compared with BDD based benzodithiophene copolymer (asy-BDTBP-BDD), PBNO and PBNS show similar LUMO energy levels, −3.59 eV and −3.63 eV, respectively, PBNO and PBNS show higher HOMO energy levels, which are −5.25 eV and −5.37 eV, respectively. PBNO blended with fullerene acceptor PC71BM exhibited similar power conversion efficiency (PCE) compared to the copolymer asy-BDTBP-BDD (4.64%). The PCE is 4.71% with short-circuit current density (JSC) of 9.85 mA cm−2, open-circuit voltage (VOC) of 0.784 V and fill factor (FF) of 60.98%. Encouragingly, PBNS presented an obviously enhanced PCE in PC71BM system PSCs, and PCE boosted to 7.58% (JSC, 12.40 mA cm−2; VOC, 0.865 V; FF, 70.83%). This work shows that analogues of excellent molecules have huge photovoltaic potential, and that side-chain modification has a significant impact on improving the photovoltaic performance of PSCs.

Improved performance of ternary blend polymer solar cells via work function tuning and suppressed interface recombination using hybrid PEDOT:PSS-graphene oxide hole transport layer

In this work, we present a solution-processed poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate)-graphene oxide (PEDOT:PSS-GO) composite as a novel hole transporting material with excellent hole extraction properties which boost the performance of ternary blend polymer solar cells (TPSCs). TPSCs employing ternary blend active layer composed of two conjugated polymer donors i.e., poly(3-hexyl)thiophene):poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2–6-diyl)] (P3HT:PTB7-th) blended with organic acceptor [6,6]-phenyl C71-butyric-acid-methyl-ester (PC71BM) have shown high performance when PEDOT:PSS-GO is used as hole transport layer (HTL). The best TPSC, ITO/PEDOT:PSS-GO(1:1)/P3HT:PTB7-th:PC71BM(0.3:0.7:1)/LiF/Al, has showed improved performance with power conversion efficiency (PCE) as high as 7.1% and external quantum efficiency of 70–80% in a broad wavelength range of 350–800 nm. There is an increment of 55% in PCE compared to TPSCs with PEDOT:PSS-only HTL. The improvement in performance of TPSCs with PEDOT:PSS-GO HTLs is predominantly attributed to the better charge extraction and carrier collection owing to significantly reduced photo-generated exciton lifetime, tuned work function, reduced potential barrier at HTL/active layer interface, remarkably improved film morphology, and increased conductivity of PEDOT:PSS-GO films. PEDOT:PSS-GO HTLs significantly boost the performance and lifetime stability of (P3HT:PTB7-th:PC71BM) ternary blend-based TPSCs. Our work demonstrate the superior hole transport properties of PEDOT:PSS-GO over conventional PEDOT:PSS HTLs for the accelerating development of TPSCs.

Aggregation Tuning with Heavily Fluorinated Donor Polymer for Efficient Organic Solar Cells

The fluorination/sulfofication-induced effect in the photovoltaic polymer solar cells (PSCs) needs to be paid much attention. In this work, a new donor polymer PBDB-PS2F was synthesized by heavily fluorinated and decorated S atom on the side chain of benzo[1,2-b:4,5-b']dithiophene (BDT) unit to explore the internal combined effect of F&S on the photoelectric performance. It was found that the heavy fluorination on the side chain could make PBDB-PS2F achieve a low highest occupied molecule orbital (HOMO) energy level of -5.72 eV and weaken the torsion of the main chain and effectively increase the intermolecular π-π* transition. Encouragingly, compared with the counterpart polymer PBDB-PS without the fluorination, PBDB-PS2F exhibited a much intense aggregation at room temperature but showed a tendency of reduced aggregation at high temperatures. This feature gives excellent solution processability and uniform morphology in the active layer of a PBDB-PS2F-based device, enabling an outstanding photovoltaic performance with the power conversion efficiency (PCE) of 13.56% (VOC = 0.90 V, JSC = 21.53 mA/cm2, FF = 69.68%). Compared with that of the counterpart polymer PBDB-PS with no heavy fluorination, the VOC of PBDB-PS2F increased by 15.4% and the PCE increased by 30.9%. Thus, the heavy-fluorination-induced effect to construct photovoltaic polymers could be used to improve the performance of polymer solar cells.

A comprehensive study: Theoretical and experimental investigation of heteroatom and substituent effects on frontier orbitals and polymer solar cell performances

AbstractBenzochalcogendiazole derivatives are incorporated with thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) acceptor and 4,8‐diethoxybenzo[1,2‐b:4,5‐b′]dithiophene donor to synthesize tree‐component random copolymers. Four different copolymers are synthesized and their electronic, optical and photovoltaic properties are compared. Comparisons are aligned in the course of two different strategies, which are the replacement of benzochalcogendiazole moiety and the modification of side group on benzothiadiazole. Theoretical calculations by comparing the HOMO‐LUMO levels, band gaps and other electronic descriptors of pristine and 2 + 2 two acceptor‐based copolymers are investigated. Random copolymer bearing benzoxadiazole moiety, PO exhibits the highest photovoltaic performance of 8.29% with a Jsc of 14.96 mA cm−2, Voc of 0.87 V, fill factor (FF) of 63.70%. PF possesses the highest Voc with a value of 0.88 V, Jsc of 14.40 mA cm−2, power conversion efficiency (PCE) of 7.32% with 58% FF. PS exhibits average feature with Jsc 11.82 mA cm−2, Voc 0.80 V, FF 50%, and 4.72% PCE. Lowest performing selenadiazole containing random copolymer (PSe) copolymer exhibits maximum PCE as 3.65%. These results demonstrate the promising effectiveness of benzoxadiazole selection as an alternative acceptor unit and F atom substitution for the design of (A1‐D)‐(A2‐D) type random copolymers for organic solar cells.

Influence of Regioregularity on the Optoelectronic Properties of Conjugated Diketopyrrolopyrrole Polymers Comprising Asymmetric Monomers.

Two asymmetric thiophene (T)/pyridine (Py) flanked diketopyrrolopyrrole (DPP) polymers with a regiorandom and regioregular conjugated backbone are synthesized via a Stille polycondensation to investigate the effect of regioregularity on their optoelectronic properties and photovoltaic performance in fullerene-based polymer solar cells. Surprisingly, both polymers possess very similar optical bandgap, energy levels, and photovoltaic performance. These findings, combined with a factor of 19 reactivity difference between the two end groups of the asymmetric DPP monomer, intuitively suggest the formation of regular chain segments in the random polymer. However, by modeling the random polymerization reaction with a kinetic Monte Carlo (KMC) simulation, evidence is obtained for exclusive formation of a fully random polymer structure. UV–vis–NIR absorption spectra of three extended DPP chromophores, containing the donor segments (T-T-T, Py-T-Py, and Py-T-T) present in the regiorandom polymer, confirm that regioregularity of the backbone has a negligible influence on the optical properties.

Orthogonal Printable Reduced Graphene Oxide 2D Materials as Hole Transport Layers for High-Performance Inverted Polymer Solar Cells: Sheet Size Effect on Photovoltaic Properties.

Creating an orthogonal printable hole-transporting layer (HTL) without damaging the underlying layer is still a major challenge in fabricating large-area printed inverted polymer solar cells (PSCs). In this study, we prepared orthogonal-processable fluorine-functionalized reduced graphene oxide (FrGO) series with various two-dimensional sheet sizes such as large-sized FrGO (1.1 μm), medium-sized FrGO (0.7 μm), and small-sized FrGO (0.3 μm) and systematically investigated the size effect of FrGOs on the hole transport properties of PSCs. The FrGOs exhibit highly stable dispersion without change over 90 days in 2-propanol solvent, indicating very high dispersion stability. Decreasing the sheet size of FrGOs enhanced hole-transporting properties, resulting in power conversion efficiencies (PCEs) of 9.27 and 9.02% for PTB7-Th:EH-IDTBR- and PTB7-Th:PC71BM-based PSCs, respectively. Compared to devices with solution-processed poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), a 14% enhancement of PCEs was achieved. Interestingly, the PCEs of devices with the smallest FrGO sheet are higher than the PCE of 8.77% of a device with vacuum-deposited MoO3. The enhancement in the performance of PSCs is attributed to the enhanced charge collection efficiency, decreased leakage current, internal resistance, and minimized charge recombination. Finally, small-sized FrGO HTLs were successfully coated on the photoactive layer using the spray coating method, and they also exhibited PCEs of 9.22 and 13.26% for PTB7-Th:EH-IDTBR- and PM6:Y6-based inverted PSCs, respectively.

Gradual Fluorination on the Phenyl Side Chains for Benzodithiophene-Based Linear Polymers to Improve the Photovoltaic Performance.

To study the impact of introducing fluorine atoms onto the conjugated phenyl side chains of benzo[1,2-b:4,5-b']dithiophene (BDT)-based copolymers, three novel donor-π-acceptor (D-π-A) alternative polymers PE40, PE42, and PE44 were designed and synthesized. The phenyl-substituted-BDT, thieno[3,2-b]thiophene, and benzo[d][1,2,3]triazole (BTA) served as the donor, π-bridge, and acceptor units, respectively, to enable linear polymer backbones. When introducing two or four fluorine atoms into the phenyl side units of PE40, the polymers PE42 and PE44 demonstrate a gradual decrease of energy levels and an increase of crystallinity in the pristine and blend films. It was noted that the increase in fluorine atoms gradually improved the performance parameters of polymer solar cells (PSCs) with Y6 as the acceptor. The PE40:Y6 device yielded a power conversion efficiency (PCE) of up to 7.07% with a short-circuit (JSC) of 21.36 mA cm-2, an open-circuVOC) of 0.65 V, and a fill factor (FF) of 0.51, and PE42:Y6 exhibited a better PCE of 10.11% (JSC = 23.25 mA cm-2, VOC = 0.74 V, and FF = 0.59), while PE44:Y6 exhibited the best PCE of 13.62% (JSC = 25.29 mA cm-2, VOC = 0.82 V, and FF = 0.66). The suitable energy offsets between the donor and the acceptor, high and balanced charge-carrier mobility, and the optimal morphology of the blend film contributed to the high performance of PE44:Y6 combination. Our results demonstrate that introducing more fluorine atoms onto the phenyl side units of BDT is a prospective approach to break the trade-offs between VOC, JSC, and FF, and finally improve the performance of PSCs.

Efficiency enhancement in polymer solar cells using combined plasmonic effects of multi-positional silver nanostructures

Abstract Achieving high absorption enhancement in a broad wavelength range without increasing the thickness of active layer is essential for improving the performance of polymer solar cells. In this work, we report efficiency enhancement in poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno [3,4-b]thiophenediyl}): [6,6]-phenyl C71-butyric acid methyl ester active layer based polymer solar cells by incorporating silver nanostructures simultaneously in cathode buffer layer and active layer. Efficiency of the device was increased from 6.53% to 7.53% after incorporating the nanostructures. The plasmonic devices exhibited superior performance in a broad wavelength range from 450 nm to 750 nm. Photoluminescence measurements were carried out to confirm the improvement in light harvesting capability of the devices. Finite-difference time-domain simulations and Raman spectroscopy were employed to verify the electric field intensity enhancement around the nanostructures. The performance enhancement mechanism was realized based on theoretical simulations and optical measurements.

An Optimized Fibril Network Morphology Enables High-Efficiency and Ambient-Stable Polymer Solar Cells.

Morphological stability is crucially important for the long‐term stability of polymer solar cells (PSCs). Many high‐efficiency PSCs suffer from metastable morphology, resulting in severe device degradation. Here, a series of copolymers is developed by manipulating the content of chlorinated benzodithiophene‐4,8‐dione (T1‐Cl) via a random copolymerization approach. It is found that all the copolymers can self‐assemble into a fibril nanostructure in films. By altering the T1‐Cl content, the polymer crystallinity and fibril width can be effectively controlled. When blended with several nonfullerene acceptors, such as TTPTT‐4F, O‐INIC3, EH‐INIC3, and Y6, the optimized fibril interpenetrating morphology can not only favor charge transport, but also inhibit the unfavorable molecular diffusion and aggregation in active layers, leading to excellent morphological stability. The work demonstrates the importance of optimization of fibril network morphology in realizing high‐efficiency and ambient‐stable PSCs, and also provides new insights into the effect of chemical structure on the fibril network morphology and photovoltaic performance of PSCs.

Developement of highly efficient large area organic photovoltaic module: Effects of nonfullerene acceptor

Abstract To transfer spin-coating based high performance polymer solar cells (PSCs) to large area using roll-to-roll compatible solution process, it is important to understand effect of the processing method and materials on morphology of bulk-heterojunction (BHJ) films. We developed PBDB-T based PSCs modules using PC71BM or nonfullerene acceptor ITIC with blade coating. It is found that crystallization of ITIC and its following aggregation are significantly affected by solvent drying dynamics which is induced by thermal heating whereas PC71BM shows similar BHJ morphology regardless heating temperature. We studied mechanism and effects of acceptors on BHJ film forming during the coating. ITIC-solvent interaction makes ITIC to form high crystalline structures and but, large aggregated domains during slow solvent evaporation at room temperature. Such aggregated morphology of PBDB-T:ITIC is much improved to optimal morphology for effective charge generation and transporting with a 50 °C heating process. As a result, PBDB-T:ITIC photovoltaic module (active area 58.5 cm2) prepared at 50 °C showed much enhanced efficiency of 9.03% than 5.0% of room temperature processed one. This result is among the highest performance of large active-area PSC modules and provides research guidelines for efficient transfer of spin-coating based small cell technology to roll-to-roll based large-area PSC modules.