Efficient All-polymer Solar Cells Research Articles

Highly Efficient All-Polymer Solar Cells Enabled by p-Doping of the Polymer Donor

In this study, we report all-polymer solar cells enabled by a joint effect of p-doping and ternary blend strategies. We apply the p-doping strategy for two material systems based on a new polymer d...

Organoboron Polymer for 10% Efficiency All-Polymer Solar Cells

Optoelectronic polymers are always π-conjugated polymers consisting of C, H, N, S, and O elements. The main group element chemistry is a new tool to tune the optoelectronic properties of polymers. ...

Synergistic effects of the processing solvent and additive on the production of efficient all-polymer solar cells.

Ideal morphological features are of particular importance to produce high performance all-polymer solar cells (all-PSCs), in which active blends generally involve unfavorable phase separation due to complicated intermixing. Developing a suitable processing solvent and additive is an effective and versatile approach to manipulate the morphology of the blends. This study demonstrates the synergistic effects of the processing solvent and additive on the photovoltaic performances of all-PSCs composed of a conjugated copolymer J71 donor and a typical N2200 acceptor. A low boiling point chloroform (CF) solvent combined with 1% 1,8-diiodoctane (DIO) additive was identified as the optimal processing condition to treat the J71:N2200 blends. Consequently, the all-PSCs prepared from CF + 1% DIO processing achieved an outstanding efficiency of 9.34% with an ultrahigh fill factor of 77.86%, which is among the top values for the current all-PSC systems. Owing to the low JSC, just a moderate efficiency of 7.28% was achieved for the device prepared from chlorobenzene (CB) + 1% DIO processing despite its high FF. The electron microscopy tests revealed that the CF solvent was superior to the CB solvent to obtain uniform morphologies and the addition of the DIO additive could further lead to more favorable phase separation and domain size. Moreover, the results of charge generation, transport, and recombination analysis correlate well with the remarkable photovoltaic properties. Our results highlight the critical significance of selecting the appropriate processing solvent and additive to produce high performance all-PSCs.

Over 14% efficiency all-polymer solar cells enabled by a low bandgap polymer acceptor with low energy loss and efficient charge separation

A low bandgap polymer acceptor PF5-Y5 was synthesized and its all-PSCs achieved an impressive device efficiency of 14.45% with both high Voc and Jsc due to the excellent absorption coverage, small energy loss, and efficient charge separation.

Efficient all-polymer solar cells based on a narrow-bandgap polymer acceptor

A new narrow-bandgap polymerized small molecule acceptor, namely PG1, was designed and synthesized. The optimal all-polymer solar cells (all-PSCs) based PBDB-T:PG1 achieved an outstanding PCE of 11.5% with a high Voc of 0.94 V.

Bicomponent Random Approach for the Synthesis of Donor Polymers for Efficient All-Polymer Solar Cells Processed from A Green Solvent.

All-polymer solar cells (all-PSCs) can offer unique merits of high morphological stability to thermal and mechanical stress. To realize their full potential as flexible or wearable devices, it is highly desirable that the all-PSCs can be fabricated from a green solvent with simple post-treatment to avoid thermal annealing on the flexible substrate. This posed a severe challenge on material design to tune their properties with suitable solubility, aggregation, and morphology. To address this challenge, here, a simple bicomponent random approach on a D-A-type polymer donor was developed by just varying the D-A molar ratio. Under this approach, a series of new random polymers PBDTa-TPDb with different molar ratios of the D component of 2D-benzo[1,2-b:4,5-b']dithiophene (BDT) and A component of thieno[3,4-c]pyrrole-4,6-dione (TPD) were designed and synthesized. The energy levels, light absorption, solubility, and packing structure of random donors PBDTa-TPDb were found to vary substantially with the various D-A molar ratios. The devices based on PBDTa-TPDb/P(NDI2HD-T) were fabricated to explore the synergistic effects of the processing solvent and composition of D-A-type random polymers. The results show that nanoscale morphology, balanced miscibility/crystallinity of blend, and photovoltaic properties could be rationally optimized by tuning the composition of random donors. As a result, as-cast all-PSC-based optimal donor PBDT5-TPD4 achieves the best power conversion efficiency (PCE) of 8.20% processed from a green solvent, which performs better than that the reference polymer (PCE: 6.41%). This efficiency is the highest value for all-PSCs from BDT-TPD-based donors. Moreover, the optimized devices were relatively insensitive to the thickness of the active layer and exhibited good stability.

Achieving Optimal Bulk Heterojunction in All-Polymer Solar Cells by Sequential Processing with Nonorthogonal Solvents.

Developing efficient all-polymer solar cells (all-PSCs) has always been a long-standing challenge due to the unfavorable morphology caused by conventional blend casting (BC). Here, we first employ the methodology of sequential processing (SP) with nonorthogonal solvents to fabricate facilely all-PSCs. A highly crystalline polymer donor, PBDB-T, is used to construct a well-organized underlying film, while a new polymer, FPDI-BT1, is selected as the acceptor to be intercalated into the amorphous or semicrystalline regions of PBDB-T during the secondary deposition. By tuning the solvent composition for FPDI-BT1 processing, a bulk heterojunction-like configuration, rather than a traditional bilayer device, is obtained facilely without the need of further processing treatment. The extremely boosted power conversion efficiency of 7.15% from the SP device is achieved, which is more than twice as efficient as the BC analogue (3.57%). The results demonstrate that SP is a promising strategy to fabricate high-performance all-PSCs with tunable configurations of active layers.

Simple perylene diimide based polymer acceptor with tuned aggregation for efficient all-polymer solar cells

Polymer acceptors for organic solar cells have got increased attention and becoming a strong candidate to replace small molecular electron acceptors. Here, a polymer acceptor (PBDTβNPDI) was constructed with naphthyl substituted asymmetric benzo [1,2-b:4,5-b']dithiophene (BDTβN) as donor unit and simple N,N′-Bis(1-propylbutyl)-1,7-dibromoperylene-3,4:9,10-tetracarbox- diimide (PDI) as acceptor unit. The designed polymer has broad absorption spectrum and tuned aggregation with asymmetric donor unit. Then all-polymer solar cells based on PTBTz-2 electron donor and PBDTβNPDI electron acceptor were prepared. The results exhibit that the device has matched energy levels, complementary absorption spectra, and desirable crystallites and nanoscale phase separation, which result in balanced mobility, low weak bimolecular recombination, and thus obtain a remarkable power conversion efficiency of 6.14% with high short circuit current density of 13.89 mA cm−2 and decent open circuit voltage of 0.88 V. The results indicate that rational regulation of PDI polymers by asymmetric strategies can obtain ideal polymer accepters, and it has a strong potential to get better results with our in-depth research.

Efficient all-polymer solar cells based on thiazole-bridged middle band-gap polymer donor: The influence of alkyl side chain on polymer-polymer miscibility and photovoltaic performance

Abstract In this work, three middle band-gap (Eg≈1.70 eV) polymer donors featuring thiazole moiety as π bridge while different alkyl side chain modification were synthesized for all-polymer solar cell (APSC) application. The influence of the configuration of alkyl side chain (linear, branched and alkylthio) on polymer-polymer miscibility and resulting photovoltaic performance was systemically investigated. The results indicated that the miscibility of polymer-polymer pair was sensitive to the solubility of resultant polymers, which was caused by diverse alkyl side chain modification. Since then, the most soluble one (P1, modified by 2-ethylhexyl side chain) could produce efficient as-cast APSC device with best PCE of 6.42%, accompanying with high Voc of 0.88 V and Jsc of 14.22 mA cm−2. This work revealed that while the incorporation of thiazole π bridge into quinoid-based polymer proves to be an efficient molecule design strategy, suitable alkyl side chain modification is also important to enhance polymer-polymer miscibility.

Vertical Distribution to Optimize Active Layer Morphology for Efficient All-Polymer Solar Cells by J71 as a Compatibilizer

From the miscibility viewpoint, the mechanism of how the third polymer influences the morphology evolution of an active layer composed of a polymer donor and a polymer acceptor remains to be unknow...

11.2% Efficiency all-polymer solar cells with high open-circuit voltage

Herein, we fabricated all-polymer solar cells (all-PSCs) based on a fluorinated wide-bandgap p-type conjugated polymer PM6 as the donor, and a narrow bandgap n-type conjugated polymer PZ1 as the acceptor. In addition to the complementary absorption and matching energy levels, the optimized blend films possess high cystallinity, predominantly face-on stacking, and a suitable phase separated morphology. With this active layer, the devices exhibited a high V oc of 0.96 V, a superior J sc of 17.1 mA cm−2, a fine fill factor (FF) of 68.2%, and thus an excellent power conversion efficiency (PCE) of 11.2%, which is the highest value reported to date for single-junction all-PSCs. Furthermore, the devices showed good storage stability. After 80 d of storage in the N2-filled glovebox, the PCE still remained over 90% of the original value. Large-area devices (1.1 cm2) also demonstrated an outstanding performance with a PCE of 9.2%, among the highest values for the reported large-area all-PSCs. These results indicate that the PM6 : PZ1 blend is a promising candidate for scale-up production of large area high-performance all-PSCs.

New Random Copolymer Acceptors Enable Additive-Free Processing of 10.1% Efficient All-Polymer Solar Cells with Near-Unity Internal Quantum Efficiency

Finding effective molecular design strategies to optimize the active layer blend morphology is among the long-standing challenges in developing efficient all-polymer solar cells (all-PSCs). Here we show that new biselenophene/selenophene-linked naphthalene diimide random copolymer acceptors BSSx (x = 10, 20, 50) facilitate the achievement of high-performance all-PSCs without the use of any solution processing additive. Blends of BSS10 with donor polymer PBDB-T combined 10.1% power conversion efficiency with 97% internal quantum efficiency and 0.59 eV optical band gap energy loss (Eloss). BSS10- and BSS20-based devices have the best combination of high external quantum efficiency (>85%) and small Eloss (<0.6 eV) among all-PSCs yet reported. The results demonstrate that the blend morphology, charge carrier mobilities, and photovoltaic properties of all-PSCs could be rationally optimized by means of a synthetic variable—the random copolymer composition.

Efficient All-Polymer Solar Cells based on a New Polymer Acceptor Achieving 10.3% Power Conversion Efficiency

Here we demonstrate efficient all-polymer solar cells (all-PSCs) based on a polymer acceptor named PFBDT-IDTIC. By combining PFBDT-IDTIC with a fluorinated donor polymer (PM6), a high power conversion efficiency of 10.3% can be achieved, which is the highest value reported to date for single-junction all-PSCs. This performance can be attributed to its good absorption property (absorption coefficient: 2.74 × 105 cm–1) and high electron mobility of PFBDT-IDTIC. It is also found that the choice of donor polymer has major impacts on the performance of the cell. By replacing PBDB-T with its fluorinated counterpart, PM6, the VOC, JSC, and FF of the devices were all improved, which can be attributed to the deeper HOMO level of PM6 and more crystalline and pure domains of the active layer blends. Our study provides a promising polymer acceptor for all-PSCs and also shows that selecting a matching donor polymer is important in achieving the optimal all-PSC performance.

Understanding the impact of side-chains on photovoltaic performance in efficient all-polymer solar cells

We performed side-chain fluorination and alkylthio substituent in a template conjugated polymer and further investigate their impact on polymer–polymer solar cell performance.

Double B←N bridged bipyridine-containing polymer acceptors with enhanced electron mobility for all-polymer solar cells

Two novel polymer electron acceptors based on double B←N bridged bipyridine with enhanced electron mobilities were synthesized for efficient all-polymer solar cells.

Poly(naphthalene diimide-alt-bithiophene) Prepared by Direct (Hetero)arylation Polymerization for Efficient All-Polymer Solar Cells

A high molecular weight alternating naphthalene diimide–bithiophene copolymer (poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (PNDIOD-T2)) has been prepared by direct (hetero)arylation polymerization (DHAP). Its structure and properties were investigated in comparison with the Stille-prepared commercial analog, N2200. It was found that the new DHAP-derived PNDIOD-T2 and known N2200 have similar optical absorption spectra and HOMO/LUMO energy levels but slightly different 1H NMR spectra. Inverted all-polymer solar cells using PNDIOD-T2 as the acceptor and PCE12 or PCE10 as the donor polymer showed slightly superior performances compared to similar N2200 devices. All-polymer solar cells with 7.3% efficiency could be achieved with PNDIOD-T2 blends without the use of a processing additive. These results demonstrate that low-cost and eco-friendly DHAP-based n-type semiconducting polymers are promising for developing high performance all-polymer sola...

8.0% Efficient all-polymer solar cells based on novel starburst polymer acceptors

The polymer N2200, with its π-conjugated backbone composed of alternating naphthalene diimide (NDI) and bithiophene (DT) units, has been widely used as an acceptor for all-polymer solar cells (all-PSCs) owing to its high electron mobility and suitable ionization potential and electron affinity. Here, we developed two naphthalene diimide derivatives by modifying the molecular geometry of N2200 through the incorporation of a truxene unit as the core and NDI-DT as the branches. These starburst polymers exhibited absorption spectra and molecular orbital energy levels that were comparable to N2200. These copolymers were paired with the wide-bandgap polymer donor PTzBI-O to fabricate all-polymer solar cells (all-PSCs), which displayed impressive power conversion efficiencies up to 8.00%. The improved photovoltaic performances of all-PSCs based on these newly developed starburst acceptors can be ascribed to the combination of increased charge carrier mobilities, reduced bimolecular recombination, and formation of more favorable film morphology. These findings demonstrate that the construction of starburst polymer acceptors is a feasible strategy for the fabrication of high-performance all-PSCs.

Cross-conjugated n-type polymer acceptors for efficient all-polymer solar cells.

We designed and synthesized a series of n-type cross-conjugated polymers with a donor-π-bridge-acceptor structure (D-π-bridge-A) which can be used as electron-accepting materials to construct efficient all-polymer solar cells (all-PSCs). The two-dimensional architecture allows for the formation of cross-conjugation, which is favorable for charge carrier transport and light harvesting. Bulk-heterojunction all-PSCs based on these cross-conjugated electron-accepting polymers and PTB7-Th as the electron-donating polymer achieve an impressive power conversion efficiency of 5.55%. This cross-conjugated architecture provides a new molecular design strategy for n-type conjugated polymers.

Novel perylene diimide-based polymers with electron-deficient segments as the comonomer for efficient all-polymer solar cells

Two novel acceptor–acceptor (A–A) type polymeric electron acceptors, PPDI-DTBT and PFPDI-DTBT, which contain perylene diimide (PDI) and fused PDI (FPDI) with electron deficient 4,7-dithienyl-2,1,3-benzothiadiazole (DTBT) units, respectively, are designed and synthesized to investigate their application in all-polymer solar cells (all-PSCs).

All-Polymer Solar Cells Based on a Conjugated Polymer Containing Siloxane-Functionalized Side Chains with Efficiency over 10.

A novel wide-bandgap conjugated copolymer based on an imide-functionalized benzotriazole building block containing a siloxane-terminated side-chain is developed. This copolymer is successfully used to fabricate highly efficient all-polymer solar cells (all-PSCs) processed at room temperature with the green-solvent 2-methyl-tetrahydrofuran. When paired with a naphthalene diimide-based polymer electron-acceptor, the all-PSC exhibits a maximum power conversion efficiency (PCE) of 10.1%, which is the highest value so far reported for an all-PSC. Of particular interest is that the PCE remains 9.4% after thermal annealing at 80 °C for 24 h. The resulting high efficiency is attributed to a combination of high and balanced bulky charge carrier mobility, favorable face-on orientation, and high crystallinity. These observations indicate that the resulting copolymer can be a promising candidate toward high-performance all-PSCs for practical applications.