Promising Power Conversion Efficiency Research Articles

High-Polarizability Organic Ferroelectric Materials Doping for Enhancing the Built-In Electric Field of Perovskite Solar Cells Realizing Efficiency over 24.

The built-in electric field (BEF) intensity of silicon heterojunction solar cells can be easily enhanced by selective doping to obtain high power conversion efficiencies (PCEs), while it is challenging for perovskite solar cells (pero-SCs) because of the difficulty in doping perovskites in a controllable way. Herein, an effective method is reported to enhance the BEF of FA0.92 MA0.08 PbI3 perovskite by doping an organic ferroelectric material, poly(vinylidene fluoride):dabcoHReO4 (PVDF:DH) with high polarizability, that can be driven even by the BEF of the device itself. The polarization of PVDF:DH produces an additional electric field, which is maintained permanently, in a direction consistent with that of the BEF of the pero-SC. The BEF superpositioncan more sufficiently drive the charge-carrier transport and extraction, thus suppressing the nonradiative recombination occurring in the pero-SCs. Moreover, the PVDF:DH dopant benefits the formation of a mesoporous PbI2 film, via a typical two-step processing method, thereby promoting perovskite growth with high crystallinity and a few defects. The resulting pero-SC shows a promising PCE of 24.23% for a 0.062 cm2 device (certified PCE of 23.45%), and a remarkable PCE of 22.69% for a 1 cm2 device, along with significantly improved moisture resistances and operational stabilities.

Porphyrin-Based All-Small-Molecule Organic Solar Cells With Absorption-Complementary Nonfullerene Acceptor

It is crucial to minimize the absorption overlap between donor and acceptor for high-efficiency all-small-molecule organic solar cells with high current densities. Considering strong absorption of nonfullerene acceptors 2,2.-((2Z,2?Z)-((4,4,9,9-tetrah exyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b.]dithiophene-2,7-diyl)bis (methanylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IDIC) in the ranges of 650–750 nm, two porphyrin unit-based small molecules containing diketopyrrolopyrrole groups (Dipor and Por) are selected as the electron donor materials because of their weak absorption in this region. Porphyrin dimer Dipor displays a broad photon response from 300 to 1000 nm in the films and its absorption deficiency between the Soret and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -bands could be perfectly compensated by nonfullerene acceptors IDIC, while monomer Por shows partial overlapping absorption to IDIC in ranges of 650–700 nm and its absorption edge locates at ∼900 nm. The higher compatibility of porphyrin dimer Dipor and IDIC results in a promising power conversion efficiency of 8.3% with a high short-circuit current density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_sc</i> ) of 20.2 mA cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> , whereas the devices based on Por: IDIC show a lower power conversion efficiency of 6.3%.

On the role of carboxylated polythiophene in defect passivation of CsPbI 2 Br surface for efficient and stable all‐inorganic perovskite solar cells

Improved film surface is a prerequisite to achieve high photovoltaic performance of inorganic perovskite solar cells because defective (under-coordinated) lead ions derived from imperfect lattice structure of the film surface or grain boundaries the principal nonradiative recombination centers in the inorganic perovskite absorber. In this study, we suggest poly[3-(4-carboxybutyl)thiophene-2,5-diyl] (P3CT), a carboxylated p-type conjugated polymer, as a passivating agent of the CsPbI2Br layer to tailor electronic properties of a perovskite absorber. With the P3CT passivation, the defective sites of the perovskite film surface were improved and stabilized, which can suppress nonradiative recombination to promote charge transport of CsPbI2Br-based all-inorganic perovskite solar cells. Consequently, the P3CT passivation delivers a power conversion efficiency (PCE) of 12.25% and decent long-term stability of CsPbI2Br perovskite solar cells, which surpasses the pristine device without the passivation. The electricity generation capability under indoor light source of the passivated device is also studied, demonstrating a promising PCE of 27.47%. This work unveils the role of P3CT as a passivating agent to passivate the defective sites of CsPbI2Br perovskite film surface and grain boundaries, which facilitates charge transport and reduced carrier recombination of CsPbI2Br absorber in solar cell devices.

Highly Semitransparent Indoor Nonfullerene Organic Solar Cells Based on Benzodithiophene‐Bridged Porphyrin Dimers

Two acceptor‐donor‐acceptor‐based porphyrin dimers, C8TEBDT‐2P and C8TBDT‐2P, are presented as donors for high‐performance semitransparent indoor organic photovoltaics. Both compounds vary in that benzodithiophene (BDT) bridged the two porphyrins at the meso‐carbon directly for the latter with a less planar structure, and via ethynylene for the former with a more planar structure. As a result, the C8TEBDT‐2P exhibits a more red‐shifted absorption profile from 400 to 800 nm than the C8TBDT‐2P from 400 to 700 nm due to stronger π‐conjugation. Using indaceno‐dithiophene‐indene‐dimalononitrile (IDIC) as a nonfullerene acceptor, the blend film C8TEBDT‐2P:IDIC shows a promising power conversion efficiency (PCE) of 12.3% under indoor (300 lux light‐emitting diode) and a PCE of 7.46% under one sun illuminations. The improved efficiency of the device C8TEBDT‐2P: IDIC is mainly due to highly ordered surface morphology, that leads in efficient charge separation, faster charge transport, and less charge recombination. Furthermore, the photopic properties indicate that both devices have good transparency and chromaticity, with an average visible transmittance value of 70% for C8TEBDT‐2P:IDIC and 73% for C8TBDT‐2P:IDIC. This study enriches the pool of porphyrin donors for highly semi‐transparent indoor nonfullerene organic solar.

Donor–Acceptor Type Polymer Bearing Carbazole Side Chain for Efficient Dopant‐Free Perovskite Solar Cells

AbstractIn conventional n–i–p perovskite solar cells (PVSCs), electron donor (D)–acceptor (A) polymers have been found to be potential substitutes for doped spiro‐based small molecule hole‐transporting materials (HTMs) due to their excellent performance in hole mobility, film formability, and stability. Herein, a benzo[1,2‐b:4,5‐b′]dithiophene (BDT)‐benzodithiophene‐4,8‐dione (BDD) copolymer PBDB‐Cz is developed by employing carbazole as the conjugated side chain of BDT. PBDB‐O and PBDB‐T with alkoxy and thiophene as the side chain of BDT, respectively, are also synthesized and studied for comparison. The synergistic effect of the carbazole side chain and the BDT‐BDD backbone to promote hole transport properties is found in PBDB‐Cz. The carbazole side chain enhances both coplanarity and interaction of polymer chains, while simultaneously deepening energy levels and improving the hole mobility of the polymeric HTM. Consequently, PBDB‐Cz outperforms two counterparts, exhibiting a promising power conversion efficiency (PCE) of 22.06%. Notably, the PBDB‐Cz also improves the device stability, and the devices can retain more than 90% of their initial PCEs after being stored at ambient conditions for 100 days. To the best of the authors’ knowledge, this is the first report to incorporate carbazole into D–A polymeric HTM by side chain engineering.

ZrSnO4: A Solution-Processed Robust Electron Transport Layer of Efficient Planar-Heterojunction Perovskite Solar Cells

A robust electron transport layer (ETL) is an essential component in planar-heterojunction perovskite solar cells (PSCs). Herein, a sol-gel-driven ZrSnO4 thin film is synthesized and its optoelectronic properties are systematically investigated. The optimized processing conditions for sol-gel synthesis produce a ZrSnO4 thin film that exhibits high optical transmittance in the UV-Vis-NIR range, a suitable conduction band maximum, and good electrical conductivity, revealing its potential for application in the ETL of planar-heterojunction PSCs. Consequently, the ZrSnO4 ETL-based devices deliver promising power conversion efficiency (PCE) up to 19.05% from CH3NH3PbI3-based planar-heterojunction devices. Furthermore, the optimal ZrSnO4 ETL also contributes to decent long-term stability of the non-encapsulated device for 360 h in an ambient atmosphere (T~25 °C, RH~55%,), suggesting great potential of the sol-gel-driven ZrSnO4 thin film for a robust solution-processed ETL material in high-performance PSCs.

Simple Additive to MAPbI3 Solution that Enhances Film Quality of Mini‐Module Perovskite Solar Cells Fabricated under Moderate Humidity

An additive to perovskite material can play a crucial role in the fabrication of perovskite solar cells (PSCs); the additive treatment investigated herein produces promising overall power conversion efficiency (PCE) enhancements. Currently, the fabrication of PSCs is mainly carried out under the dry air of a glove box to avoid moisture adsorption by methylammonium lead iodide perovskites; these tight restrictions in how PSCs are fabricated hinder the possibility of their commercialization. In this study, a technique that uses C12F4N4 as an additive to the MAPbI3 for the one‐step deposition of perovskite layers under moderate humidity is presented; this approach is able to achieve high‐quality perovskite films despite the adverse condition. The added C12F4N4 bridges the gaps between the MAPbI3 grain boundaries and significantly enhances all the photovoltaic parameters compared to using pristine methylammonium lead iodide; this method even eventually enhances the overall PCE. Both, single‐cell and optimized five‐cell integrated mini‐module devices in moderately humid conditions are fabricated. This facile method presents new possibilities for scaling up PSCs production in humid environments.

Surface Reconstruction for Stable Monolithic All‐Inorganic Perovskite/Organic Tandem Solar Cells with over 21% Efficiency

AbstractThe construction of monolithic two‐terminal tandem solar cells (2T TSCs) offers the possibility of pursuing high power conversion efficiency (PCE) by overcoming the single‐junction Shockley–Queisser limit in photovoltaics. However, little attention is paid to simultaneously improve the stability by utilizing the complementary properties of various photoactive layers. Here, beyond the stacked photoactive layers featuring complementary absorption, all‐inorganic perovskite (CsPbI1.8Br1.2) is chosen as the photoactive layer of the front wide‐bandgap subcell for its intrinsic high thermal stability and ultraviolet (UV)‐filtering function to address the burn‐in and UV degradation of organic rear subcells. To realize their monolithic integration, the charge recombination efficiency in the interconnecting layer (ICL) between the two types of subcells is tentatively improved by surface reconstruction of all‐inorganic perovskite using trimethylammonium chloride. The repaired CsPbI1.8Br1.2 surface enables effective suppression of nonradiative recombination and facilitates hole transport, providing efficient charge recombination in the ICL in the 2T TSC. As a result, the all‐inorganic perovskite/organic 2T TSC delivers a promising PCE of 21.04%, accompanied by an ultrahigh open‐circuit voltage (Voc) of 2.05 V, which is nearly equal to the superposition of the respective Voc values of the subcells. More importantly, the 2T TSC simultaneously shows outstanding operational and UV stabilities.

Triarylborane-BODIPY conjugate: An efficient non-fullerene electron acceptor for bulk heterojunction organic solar cell

A new X-type, structurally twisted, highly soluble TAB-BODIPY based electron acceptor (BDY) is designed and synthesized. Organic solar devices are fabricated using poly(3-hexylthiophene-2,5-diyl) (P3HT) as donor polymer and BDY as an electron acceptor. A promising power conversion efficiency of 4.46% is obtained for this new class of acceptor, which is the first-ever reported on TAB-BODIPY as a non-fullerene acceptor in organic solar cells.

First-principles calculation on electronic properties of Bismuth-halide inorganic perovskites for solar cell

Solar energy is a commonly used alternate source of energy and it can be utilized based on the principle of the photovoltaic effect. The photovoltaic effect converts sun energy into electrical energy using photovoltaic devices (solar cells). A solar cell device should have high efficiency and a long lifetime to be commercially beneficial. Presently, silicon and thin-film solar cells are widely employed. The crystalline solar cells are more efficient but they are also expensive. Thin-film solar cells are formed by placing one or more thin layers of photovoltaic materials on different substrates. Although these cells have a lower cost, they are also less efficient compared to Si-based solar cells. Organic-inorganic hybrid lead halide perovskite solar cells are one of the most promising low-cost power conversion efficiency technologies that could exceed the 26% threshold. However, the lack of environmental stability and of high lead toxicity are the main bottlenecks that impede the future industrialization and commercialization hybrid lead halide perovskite. Hence It is important to achieve high power conversion efficiency while also maintaining stability and non-toxicity in the development of new lead-free perovskite materials.

Flexibility of Room-Temperature-Synthesized Amorphous CdO-In2O3 Alloy Films and Their Application as Transparent Conductors in Solar Cells.

Due to their low-temperature deposition, high mobility (>10 cm2/V·s), and electrical conductivity, amorphous ionic oxide semiconductors (AIOSs) have received much attention for their applications in flexible and/or organic electro-optical devices. Here, we report on a study of the flexibility of CdO-In2O3 alloy thin films, deposited on a polyethylene terephthalate (PET) substrate by radio frequency magnetron sputtering at room temperature. Cd1-xInxO1+δ alloys with the composition of x > 0.6 are amorphous, exhibiting a high electron mobility of 40-50 cm2/V·s, a low resistivity of ∼3 × 10-4 Ω·cm, and high transmittance over a wide spectral window of 350 to >1600 nm. The flexibility of both crystalline and amorphous Cd1-xInxO1+δ films on the PET substrate was investigated by measuring their electrical resistivity after both compressive and tensile bending with a range of bending radii and repeated bending cycles. Under both compressive and tensile bending with Rb = 16.5 mm, no significant degradation was observed for both the crystalline and amorphous films up to 300 bending cycles. For a smaller bending radius, the amorphous film shows much less electrical degradation than the crystalline films under compressive bending due to less film delamination at the bending sites. On the other hand, for a small bending radius (<16 mm), both crystalline and amorphous films degrade after repeated tensile bending, most likely due to the development of microcracks in the films. To demonstrate the application of amorphous Cd1-xInxO1+δ alloy in photovoltaics, we fabricated perovskite and bulk-heterojunction organic solar cells (OSCs) on glass and flexible PET utilizing amorphous Cd1-xInxO1+δ layers as transparent electrodes. The organic-inorganic hybrid perovskite solar cells (PSCs) exhibit a power conversion efficiency (PCE) of ∼11 to 12% under both front and back illumination, demonstrating good bifacial performance with bifaciality factor >90%. The OSCs fabricated on an amorphous Cd1-xInxO1+δ-coated flexible PET substrate achieve a promising PCE of 12.06%. Our results strongly suggest the technological potentials of amorphous Cd1-xInxO1+δ as a reliable and effective transparent conducting material for flexible and organic optoelectronic devices.

In situ synthesis of Ti3C2Tx MXene/CoS nanocomposite as high performance counter electrode materials for quantum dot-sensitized solar cells

Low electrocatalytic activity and/or high charge transfer resistance of counter electrodes (CEs) in quantum-dot-sensitized solar cells (QDSSCs) are the main reasons for the low photovoltaic performance. Herein, the CoS nanoparticles are anchored on the MXene (Ti3C2Tx) via a simple in-situ hydrothermal reaction process. It is the first attempt to use the MXene/CoS as a highly electrocatalytic CE for QDSSCs. The QDSSCs with a MXene/CoS CE shows a significant enhancement in cell performances and yields a promising power conversion efficiency (PCE) of 8.09% compared with that of the QDSSCs with bare CoS (5.77%) and bare MXene (4.25%) CEs. The significant enhancement of PCE value is mainly attributed to the synergistic effects of the unique layered morphology of conductive MXene nanosheets and its cocatalysis with CoS nanoparticles. The coupling of layered MXene with small CoS nanoparticles (~15 nm) provides abundant catalytic active sites. The improved mesoporous morphology contributes a high specific surface area and fast electron transfer channels for Sx2− reduction. Consequently, the MXene/CoS nanocomposite can be utilized as an effective agent to boost up the photovoltaic performance of QDSSCs.

Low-bandgap nonfullerene acceptor based on thieno[3,2-b]indole core for highly efficient binary and ternary organic solar cells

A low-bandgap nonfullerene acceptor (NFA) TIT-2FIC based on thieno[3,2-b]indole-thiophenes core has been developed. Compared with the analogue NFAs DTC(4Ph)-4FIC and IT-4F, TIT-2FIC exhibited remarkably red-shifted absorption, and up-shifted HOMO energy level. In addition, TIT-2FIC showed interesting universal miscibility with the donors nonfluorinated PBDB-T and fluorinated PM6, therefore the corresponding organic solar cells achieved promising power conversion efficiencies (PCEs) of 11.80% and 13.00%, respectively, which are higher compared to the counterpart IT-4F based cells. Furthermore, the ternary PM6:TIT-2FIC:Y6 cell pronounced a high PCE of 17.22%, being significantly improved from that of 16.04% for the binary PM6:Y6 cell. Similar improvement in PCEs from 13.41% to 14.46% was also observed in the ternary PM6:TIT-2FIC:IT-4F cell with TIT-2FIC as the third component. These results indicated that TIT-2FIC is universally applicable as an acceptor with nonfluorinated or fluorinated polymer donor materials in both binary and ternary cells.

Highly Efficient Binary Solvent Additive‐Processed Organic Solar Cells by the Blade‐Coating Method

AbstractBlade‐coating, a prototype tool for slot‐die coating is a promising technique showing high compatibility with large‐area roll‐to‐roll coating. Here, a high‐performance PM6:Y6‐based device is fabricated with chlorobenzene (CB) through a novel binary solvent additive (1‐chloronaphthalene (CN):diphenyl ether (DPE)). It can be found that the binary solvent additive can improve the crystallinity of the acceptor and forms a better phase separation domain, which would promote the effective separation of charge and inhibit charge recombination. As a result, high power conversion efficiency (PCE) of 15.77% can be achieved with the spin‐coating method, which is similar to the best organic solar cells (OSCs) processed with chloroform (CF) solution. Moreover, a blade‐coated OSC is also processed with CB and demonstrates a promising PCE of 11.69% with large‐area device (1.2 cm2). These results are critical for the large‐scale production of highly efficient OSCs.

Fine-tuned crystallinity of polymerized non-fullerene acceptor via molecular engineering towards efficient all-polymer solar cell

Despite remarkable advancement made by virtue of “polymerized non-fullerene acceptor” strategy in all-polymer solar cells (all-PSCs) recently, the tuning of polymer crystallinity via molecular design to optimize the nanostructured blend morphology remains challenging for boosting the short-circuit current density (JSC). Herein, through systematically optimizing the central core and π-spacer, we present a facile method to regulate the solid-state crystallinity of these emerging polymer acceptors. Specifically, we have synthesized a new family of polymerized non-fullerene acceptors named PY-2T and PY-2T2Cl by copolymerizing the Y5-derivative with bithiophene or chlorinated bithiophene. Compared to the previously used IDIC-based polymer named PIDIC-2T, the extended D-A-D fused ring core renders PY-2T with significantly red-shifted optical absorption and up-shifted energy levels, leading to simultaneously improved JSC and open circuit voltage (VOC) in the resultant all-PSCs. More importantly, the chlorinated PY-2T (PY-2T2Cl) endows the desirable phase separated blend morphology with favorable film crystallinity when paired with polymer donor PBDB-T, thus PY-2T2Cl based all-PSCs delivers a promising power conversion efficiency of approaching ~10% with a greatly enhanced JSC of 16.3 mA/cm2 and high VOC of 0.87 eV. This systematic study provides an insight into the effect of central core and π-spacer on the film crystallinity for developing high-performance polymerized non-fullerene acceptors, and also highlights the importance of both absorption and morphology in boosting the desired JSC in all-PSCs.

Modulating Crystallinity and Miscibility via Side‐chain Variation Enable High Performance All‐Small‐Molecule Organic Solar Cells

Main observation and conclusionSide‐chain engineering as one of the most important molecular design strategies has been widely used to improve photovoltaic efficiency of active layer materials. Herein, a series of acceptor‐π‐donor‐π‐acceptor typed small molecule (SM)‐donors (SL1, SL2, SL3, and SL4), on the basis of high‐performance SM‐donor BTTzR (SL1) with thiazolo[5,4‐d]thiazole as the π‐bridging units and 3‐butylrhodanine as the terminal electron‐withdrawing groups, were designed and synthesized to study the effect of the side‐chain substitutions of BDT‐T on the photovoltaic performance. The investigation shows that the side‐chain engineering has no obvious effect on the molecular absorption spectrum and energy levels but significantly influences on the molecular orientation and packing, and the compatibility with the acceptor Y6. Among these SM‐donors neat films, SL1 and SL3 with two mixed branched and straight alkyl chains exhibit stronger crystallization in the face‐on direction, and SL4 with two shorter alkyl chains achieves more compact packing. In the Y6‐based blend films, three SM‐donors (SL1, SL3, and SL4) with double alkyl chains on thienyl of BDT‐T have much better compatibility compared to SL2 with single long alkyl chain, while their compatibility increases with the increase of alkyl chain length. The stronger crystallization, moderate molecular packing, and better blend compatibility of SL1 offer higher Jsc of 23.2 mA·cm–2 and fill factor (FF) of 0.68 in the Y6‐based all‐small‐molecule organic solar cells (all‐SM‐OSCs). Ultimately, the SL1:Y6‐based devices achieved a promising power conversion efficiency of 13.9%, which is much higher than that of 11.5% from the SL2:Y6‐based devices (Jsc = 21.5 mA·cm–2 and FF = 0.60). This work indicates that modulating the side chain of SM‐donors is a promising strategy to obtain efficient all‐SM‐OSCs.

Star-shaped D-π-D hole-transporting materials regulated by molecular planarity and their application in efficient perovskite solar cells

During the molecular design of hole-transporting material (HTM) for perovskite solar cells (PSCs), the planarity is the critical factor, which can regulate multiple properties affecting the photovoltaic performance, including the hole transport and morphology uniformity. Herein, a planar carbazole group is applied as the core unit to obtain a star-shaped HTM CS-43. Owning to the planar core unit, CS-43 shows more negative HOMO level, which is beneficial to obtain high photovoltage, with respect to the twisted HTM CS-42. More importantly, compared with the twisted HTM CS-42, the planar core unit of CS-43 strengthens the trend of intermolecular stacking, thus resulting in the significant improvement in hole mobility. Furthermore, with the planar core unit, the morphology of CS-43 film is also improved. As an overall result of high hole mobility and excellent film morphology, the PSC based on CS-43 present a quite promising power conversion efficiency of 15.87% with long-term stability, which is over 40% higher than that of PSC prepared by twisted CS-42. Accordingly, the planarity improvement in core unit can optimize both the hole transporting and morphology performance, providing us a powerful strategy for the further development of small molecule HTM.

Constructing CdS-Based Electron Transporting Layers With Efficient Electron Extraction for Perovskite Solar Cells

The electron transporting layer (ETL) is a critical component in perovskite solar cells (PSCs) and plays an important role in extracting and transporting electrons. However, the commonly used wide-bandgap metal oxides (TiO2, ZnO, SnO2, etc.) often involve undesirable photocatalytic activity towards perovskite materials under UV light, which would undermine the long-term stability of PSCs. In this article, nonoxide CdS ultra-thin films were deposited onto conducting substrates through chemical bath deposition to serve as ETLs. It is revealed that the subsequent CdCl2 treatment followed by annealing is not essential to CdS ETLs for PSCs; this fact is quite different from the scenario demonstrated for conventional thin-film solar cells. Moreover, a compact TiO2 (c-TiO2) blocking layer was introduced between the conducting substrate and the CdS layer to further enhance the electron extraction capability of ETLs and boost the photovoltaic performance of PSCs. Through careful morphology, optical and electrical characterizations, it is found that the presence of the c-TiO2 underlayer avoids the partially exposure of substrate bumps, enlarges the subsequently deposited perovskite crystals, forms cascade energy level alignments, and accelerates the electron extraction from perovskite to ETLs. Therefore, the shunt current leakage and the charge recombination at the ETL/perovskite interface are significantly suppressed. Eventually, the CH3NH3PbI3 PSC based on the bilayer c-TiO2/CdS ETL yields a promising power conversion efficiency of 15.11%, which is much higher than that of the single-layer CdS-based device. This work delivers one of the few CdS ETL-based PSCs that exhibit efficiencies over 15%.

Regulating the Aggregation of Unfused Non-Fullerene Acceptors via Molecular Engineering towards Efficient Polymer Solar Cells.

Tuning molecular aggregation via structure design to manipulate the film morphology still remains as a challenge for polymer solar cells based on unfused non-fullerene acceptors (UF-NFAs). Herein, a strategy was developed to modulate the aggregation patterns of UF-NFAs by systematically varying the π-bridge (D) unit and central core (A') unit in A-D-A'-D-A framework (A and D refer to electron-withdrawing and electron-donating moieties, respectively). Specifically, the quantified contents of H- or J-aggregation and crystallite disorder of three UF-NFAs (BDIC2F, BCIC2F, and TCIC2F) were analyzed via UV/Vis spectrometry and grazing incidence X-ray scattering. The results showed that the H-aggregate-dominated BCIC2F with less crystallite disorder exhibited a more favorable blend morphology with polymer donor PBDB-T (poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene)-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione)]) relative the other two UF-NFAs, resulting in improved exciton dissociation and charge tranport. Consequently, photovoltaic devices based on BCIC2F delivered a promising power conversion efficiency of 12.4 % with an exceptionally high short-circuit current density of 22.1 mA cm-2 .

Photodegradation of Triple-Cation Perovskite Solar Cells: The Role of Spectrum and Bias Conditions

Despite promising power conversion efficiencies, a key barrier for the future commercialization of perovskite-based solar cells (PSCs) is their lack of stability when exposed to sunlight for extend...