An acrylated fullerene derivative for efficient and thermally stable polymer solar cells

The continuous microstructure evolution occurring in active layers of polymer-fullerene solar cells is one of the main causes for their device instability. With aim to tackle it, this work developed a new polymerizable fullerene acceptor, [6,6]-phenyl-C₆₁-butyl acrylate (PC₆₁BA). It was found that PC₆₁BA has similar light-absorption properties and HOMO and LUMO energy levels as [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM), and can be converted into insoluble oligomers upon heating at 150 °C. Polymer-fullerene solar cells using poly(3-hexylthiophene) (P3HT) as donor and PC₆₁BA as acceptor exhibited an optimized efficiency of 3.54%, the performance comparable to P3HT/PC₆₁BM cells (optimized efficiency: 3.70%). But, the former possess much better thermal stability than the latter owing to aggregation suppression by the polymerized PC₆₁BA. These results indicate that PC₆₁BA, unlike most previous reported, is a unique polymerizable fullerene derivative that can be used alone as acceptor to achieve both efficient and thermally stable polymer solar cells.     

Improved photovoltaic performance from high quality perovskite thin film grown with the assistance of PC<Subscript>71</Subscript>BM

The strategy of sequentially spin-coating a perovskite film from the perovskite precursor and an electron transporting layer of [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) is developed to simplify the fabrication procedure of perovskite solar cells. X-ray diffraction and scanning electron microscopy indicate that PC₇₁BM film on perovskite layer can retard the evaporation of dimethyl sulfoxide (DMSO) efficiently, thus prolonging the transformation of intermediate phase to perovskite crystals, leading to a high quality perovskite thin film. The solar cells with the structure of indium tin oxides (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/CH₃NH₃PbI₃/PC₇₁BM/bathocuproine (BCP)/Ag made from this simplified method exhibit a higher efficiency (12.68%) than those from the conventional one-step method (9.49%).     

The phase behavior of a polymer‐fullerene bulk heterojunction system that contains bimolecular crystals

Polymer:fullerene blends have been widely studied as an inexpensive alternative to traditional silicon solar cells. Some polymer:fullerene blends, such as blends of poly(2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene (pBTTT) with phenyl‐c71‐butyric acid methyl ester (PC₇₁BM), form bimolecular crystals due to fullerene intercalation between the polymer side chains. Here we present the determination of the eutectic pBTTT:PC₇₁BM phase diagram using differential scanning calorimetry (DSC) and two‐dimensional grazing incidence X‐ray scattering (2D GIXS) with in‐situ thermal annealing. The phase diagram explains why the most efficient pBTTT:PC₇₁BM solar cells have 75–80 wt % PC₇₁BM since these blends lie in the center of the only room‐temperature phase region containing both electron‐conducting (PC₇₁BM) and hole‐conducting (bimolecular crystal) phases. We show that intercalation can be suppressed in 50:50 pBTTT:PC₇₁BM blends by using rapid thermal annealing to heat the blends above the eutectic temperature, which forces PC₇₁BM out of the bimolecular crystal, followed by quick cooling to kinetically trap the pure PC₇₁BM phase. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

聚(3-己基噻吩)作为光谱增感层在有机太阳电池光谱响应增强中的应用

报道了利用聚(3-己基噻吩)(P3HT)作为前置缓冲层来弥补(4,8-双-(2-乙基己氧基)-苯并[1,2-b:4,5-b']二噻吩)-(4-氟代噻并[3,4-b]噻吩(PBDT-TT-F):[6,6]-苯基-C₆₁-丁酸甲酯(PC₆₁BM)共混体相异质结(BHJ)电池对450-600 nm处光谱响应不足的新的器件结构设计思路. 光谱带隙为1.8 eV的PBDT-TT-F 在550-700 nm处有很强的光谱吸收, 在有机太阳电池器件上有很好的应用潜能. 但其在350-550 nm处的吸收不强, 影响了器件对太阳光谱的利用效率. 与此相比, P3HT薄膜的光谱吸收主要在450-600 nm范围内, 同PBDT-TT-F 形成良好的互补关系. 新设计的器件外量子效率(EQE)研究结果表明, 利用P3HT 作为前置缓冲层可以与PBDT-TT-F:PC₆₁BM薄膜中的PC₆₁BM形成平面异质结, 从而拓展了器件在450-600 nm处的光谱响应范围,实现光谱增感作用. 优化P3HT的厚度为20 nm左右, 器件对外输出的短路光电流密度从11.42 mA·cm^-2提高到12.15 mA·cm^-2, 达到了6.3%的提升.     

An Oligothiophene–Fullerene Molecule with a Balanced Donor–Acceptor Backbone for High‐Performance Single‐Component Organic Solar Cells

A new balanced donor–acceptor molecule, namely, benzodithiophene (BDT)‐rhodanine‐[6,6]‐phenyl‐C₇₁ butyric acid methyl ester (Rh‐PC₇₁BM) comprising two covalently linked blocks, a p‐type oligothiophene‐containing BDT‐based moiety and an n‐type PC₇₁BM unit was designed and synthesized. The single‐component organic solar cell (SCOSC) fabricated from Rh‐PC₇₁BM molecules showed a power conversion efficiency (PCE) of 3.22 % with an open‐circuit voltage (V_oc) of 0.98 V. These results rank are among the highest values for SCOSCs based on a monomolecular material. In particular, the one‐molecule Rh‐PC₇₁BM device exhibits excellent thermal stability compared to reference Rh‐OH:PC₇₁BM device. The success of our monomolecular strategy can provide a new way to develop high‐performance SCOSCs.     

Ternary Blend Strategy for Achieving High-Efficiency Organic Photovoltaic Devices for Indoor Applications

Monomeric perylene diimide (PDI) small molecules display a high absorption coefficient and crystallinity in solid-state thin films due to strong π–π interactions between the molecules. To take advantage of these exciting properties of PDIs, N,N'-bis(1-ethylpropyl)perylene-3,4,9,10-tetracarboxylic diimide (EP-PDI) was mixed with a binary blend of PTB7 and PC₇₁BM to fabricate an efficient ternary blend, which were in turn used to produce organic photovoltaic (OPV) devices well suited to indoor applications (PTB7=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}), PC₇₁BM=[6,6]-phenyl-C₇₁-butyric acid methyl ester). We varied the PC₇₁BM/EP-PDI weight ratio to investigate the influence of EP-PDI on the optical, electrical, and morphological properties of the PTB7:PC₇₁BM:EP-PDI ternary blend. Compared with the reference PTB7:PC₇₁BM binary blend, the ternary blends showed strong optical absorption in the wavelength range in which the spectra of indoor LED lamps show their strongest peaks. The addition of EP-PDI to the binary blend was found to play an important role in altering the morphology of the blend in such a way as to facilitate charge transport in the resulting ternary blend. Apparently, as a result, the optimal PTB7:PC₇₁BM:EP-PDI-based inverted OPV device exhibited a power conversion efficiency (PCE) of 15.68 %, a fill factor (FF) of 68.5 %, and short-circuit current density (J_SC) of 56.7 μA cm⁻² under 500 lx (ca. 0.17 mW cm⁻²) indoor LED light conditions.     

Synthesis and investigation of photovoltaic properties for polymer semiconductors based on porphyrin compounds as light-harvesting units

We reported on two polymer semiconducting copolymers based on porphyrin compounds, poly[9,9-dioctylfluorene-co-5,15-bis(hexoxybenzyl)-10,20-bis(benzo-4-yl)porphyrin] (PFPor) and poly[9-(heptadecan-9-yl)carbazole-co-5,15-bis(hexoxybenzyl)-10,20-bis(benzo-4-yl)porphyrin] (PCPor), for use as organic photovoltaic materials. The thermal, optical, electrochemical, and photovoltaic properties of the two polymers were investigated. In addition, PC₆₁BM and PC₇₁BM were introduced as acceptor materials to confirm the acceptor effect in bulk heterojunction photovoltaic devices. Moreover, in order to establish acceptor effects, morphologies of polymer/PCBM blend films were analyzed through atomic force microscopy (AFM). PFPor and PCPor exhibited the best device performance with power conversion efficiencies (PCE) of 0.62% and 0.76%, respectively, upon the introduction of PC₇₁BM as the acceptor in the device where 86 wt.% of the PC₇₁BM was contained in the active layer (pol:PC₇₁BM = 1:6, w/w).     

Tailorable PC71BM Isomers: Using the Most Prevalent Electron Acceptor to Obtain High‐Performance Polymer Solar Cells

Despite being widely used as electron acceptor in polymer solar cells, commercially available PC₇₁BM (phenyl‐C₇₁‐butyric acid methyl ester) usually has a “random” composition of mixed regioisomers or stereoisomers. Here PC₇₁BM has been isolated into three typical isomers, α‐, β₁‐ and β₂‐PC₇₁BM, to establish the isomer‐dependent photovoltaic performance on changing the ternary composition of α‐, β₁‐ and β₂‐PC₇₁BM. Mixing the isomers in a ratio of α/β₁/β₂=8:1:1 resulted in the best power conversion efficiency (PCE) of 7.67 % for the polymer solar cells with PTB7:PC₇₁BM as photoactive layer (PTB7=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]]). The three typical PC₇₁BM isomers, even though sharing similar LUMO energy levels and light absorption, render starkly different photovoltaic performances with average‐performing PCE of 1.28–7.44 % due to diverse self‐aggregation of individual or mixed PC₇₁BM isomers in the otherwise same polymer solar cells.     

Donor–acceptor photovoltaic polymers based on 1,4‐dithienyl‐2,5‐dialkoxybenzene with intramolecular noncovalent interactions

Donor–acceptor (D–A) conjugated polymers bearing non‐covalent configurationally locked backbones have a high potential to be good photovoltaic materials. Since 1,4‐dithienyl‐2,5‐dialkoxybenzene ( TBT ) is a typical moiety possessing intramolecular S…O interactions and thus a restricted planar configuration, it was used in this work as an electron‐donating unit to combine with the following electron‐accepting units: 3‐fluorothieno[3,4‐b]thiophene ( TFT ), thieno‐[3,4‐c]pyrrole‐4,6‐dione ( TPD ), and diketopyrrolopyrrole ( DPP ) for the construction of such D–A conjugated polymers. Therefore, the so‐designed three polymers, PTBTTFT , PTBTTPD , and PTBTDPP , were synthesized and investigated on their basic optoelectronic properties in detail. Moreover, using [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) as acceptor material, polymer solar cells (PSCs) were fabricated for studying photovoltaic performances of these polymers. It was found that the optimized PTBTTPD cell gave the best performance with a power conversion efficiency (PCE) of 4.49%, while that of PTBTTFT displayed the poorest one (PCE = 1.96%). The good photovoltaic behaviors of PTBTTPD come from its lowest‐lying energy level of the highest occupied molecular orbital (HOMO) among the three polymers, and good hole mobility and favorable morphology for its PC₇₁BM‐blended film. Although PTBTDPP displayed the widest absorption spectrum, the largest hole mobility, and regular chain packing structure when blended with PC₇₁BM, its unmatched HOMO energy level and disfavored blend film morphology finally limited its solar cell performance to a moderate level (PCE: 3.91%). © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 689–698     

Isoindigo‐3,4‐Difluorothiophene Polymer Acceptors Yield “All‐Polymer” Bulk‐Heterojunction Solar Cells with over 7 % Efficiency

Poly(isoindigo‐alt‐3,4‐difluorothiophene) (PIID[2F]T) analogues used as “polymer acceptors” in bulk‐heterojunction (BHJ) solar cells achieve >7 % efficiency when used in conjunction with the polymer donor PBFTAZ (model system; copolymer of benzo[1,2‐b:4,5‐b′]dithiophene and 5,6‐difluorobenzotriazole). Considering that most efficient polymer‐acceptor alternatives to fullerenes (e.g. PC₆₁BM or its C₇₁ derivative) are based on perylenediimide or naphthalenediimide motifs thus far, branched alkyl‐substituted PIID[2F]T polymers are particularly promising non‐fullerene candidates for “all‐polymer” BHJ solar cells.     

Morphological study of an intrinsically stretchable photovoltaic bulk heterojunction

Thin‐film polymer solar cell consisting of [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC₇₁BM) and 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]] (PTB7) demonstrates elastic stretchability with the aid of a high boiling point additive, 1,8‐diiodooctane (DIO). The usage of DIO not only helps to form uniformly distributed nanocrystalline grains, but may also create free volumes between the nano‐grains that allow for relative sliding between the nano‐grains. The relative sliding can accommodate large external deformation. Large dichroic ratios of the optical absorption of both PC₇₁BM and PTB7 were observed under large‐strain deformation, indicating reorientation of the nanocrystalline PC₇₁BM and PTB7 polymer chains along stretching direction. The dichroic ratio decreases to nearly 1.0 as the blend was relaxed to 0% strain. Therefore, the nanometer‐size grain blending morphology provides an approach to impart stretchability to organic semiconductors that are otherwise un‐stretchable. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 814–820     

Thiazolothiazole‐containing polythiophenes with low HOMO level and high hole mobility for polymer solar cells

Two regiochemically defined polythiophenes containing thiazolothiazole acceptor unit were synthesized by palladium(0)‐catalyzed Stille coupling reaction. The thermal, electrochemical, optical, charge transport, and photovoltaic properties of these copolymers were examined. Compared to P1 with head‐to‐head coupling of two middle thiophenes, P2 with head‐to‐tail coupling of two middle thiophenes exhibits 40 nm red shift of absorption spectrum in film and 0.3 eV higher HOMO level. Both polymers exhibit field‐effect hole mobility as high as 0.02 cm² V^?1 s^?1. Polymer solar cells (PSCs) were fabricated based on the blend of the polymers and methanofullerene[6,6]‐phenyl C71‐butyric acid methyl ester (PC₇₁BM). The PSC based on P1 :PC₇₁BM (1:2, w/w) exhibits a power conversion efficiency of 2.7% under AM 1.5, 100 mW cm^?2, two times of that based on P2 :PC₇₁BM. The higher efficiency is attributed to lower HOMO (?5.6 eV) and smaller phase separation scale in P1 :PC₇₁BM blend. Tiny change in thiophene connection of P1 and P2 lead to great difference in HOMO, phase separation scale, and efficiency of their photovoltaic devices. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of D-A copolymers based on thiadiazole and thiazolothiazole acceptor units and their applications in ternary polymer solar cells

We have designed and synthesized two wide bandgap new donor-acceptor (D-A) copolymers consisting of the same alkylthiazole-substituted benzo[1,2-b;4,5-b′]dithiophene (BDTTz) donor unit and but different acceptor units, i.e., thiazolo[5,4-d]thiazole (TT_Z) ( P122 ) and 1,3,-4 thiadiazole (TDz) ( P123 ) and investigated their optical and electrochemical properties. We have employed these copolymers as donor and fullerene (PC ₇₁ BM) and narrow bandgap non-fullerene (Y6) as acceptor, to fabricate binary and ternary bulk heterojunction polymer solar cells (PSCs). The overall power conversion efficiency (PCE) of optimized binary bulk heterojunction PSCs based on P122 :Y6 and P123 :Y6 is 12.60% and 13.16%, respectively. The higher PCE for PSCs based on P123 than P122 counterparts may be associated with the broader absorption profile of the P123 and more charge carrier mobilities than that for the P122 active layer. With the incorporation of small amount of PC₇₁BM into either P122 :Y6 or P123 :Y6 binary blend, the corresponding ternary PSCs showed an overall PCE of 14.89% and 15.52%, respectively, which is higher than the binary counterparts using either Y6 or PC₇₁BM as acceptor. Incorporating the PC₇₁BM in the binary host blend increases the absorption in the 300–500 nm wavelength region, generating more excitons in the active ternary layer and helping to dissociate the excitons into free charge carriers more effectively. The more appropriate nanoscale phase separation in the active ternary layer than the binary counterpart may be one of the reasons for higher PCE.     

Carbazole‐based conjugated polymers incorporating push/pull organic dyes: Synthesis,characterization, and photovoltaic applications

We have synthesized and characterized two new carbazole‐based conjugated polymers, PCDCN and PCDTA , incorporating two strong light‐absorbing organic dyes. These polymers exhibit relatively low band gaps (～1.5 eV) and broad absorption ranges (from 300 to 700 nm). We fabricated polymer solar cells incorporating these polymers as donors and [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) as the acceptor. At a blending ratio of 1:4, we obtained power conversion efficiencies, under simulated AM 1.5 (100 mW/cm²) conditions, of 2.31% and 2.47% for the PCDCN ‐ and PCDTA ‐based devices, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and applications of cyano‐vinylene‐based polymers containing cyclopentadithiophene and dithienosilole units for photovoltaic cells

Two β‐cyano‐thiophenevinylene‐based polymers containing cyclopentadithiophene ( CPDT‐CN ) and dithienosilole ( DTS‐CN ) units were synthesized via Stille coupling reaction with Pd(PPh₃)₄ as a catalyst. The effects of the bridged atoms (C and Si) and cyano‐vinylene groups on their thermal, optical, electrochemical, charge transporting, and photovoltaic properties were investigated. Both polymers possessed the highest occupied molecular orbital (HOMO) levels of about ?5.30 eV and the lowest unoccupied molecular orbital (LUMO) levels of about ?3.60 eV, and covered broad absorption ranges with narrow optical band gaps (ca. 1.6 eV). The bulk heterojunction polymer solar cell (PSC) devices containing an active layer of electron‐donor polymers ( CPDT‐CN and DTS‐CN ) blended with an electron‐acceptor, that is, [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) or [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM), in different weight ratios were explored under 100 mW/cm² of AM 1.5 white‐light illumination. The PSC device based on DTS‐CN: PC₇₁BM (1:2 w/w) exhibited a best power conversion efficiency (PCE) value of 2.25% with V_oc = 0.74 V, J_sc = 8.39 mA/cm², and FF = 0.36. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Efficient P3HT:PC61BM solar cells employing 1,2,4-trichlorobenzene as the processing additives

The efficiency of the poly(3-hexylthiophene)(P3HT) and [6,6]-phenyl C_(61)-butyric acid methyl ester(PC_(61)BM) based organic solar cells was enhanced by using 1,2,4-trichlorobenzene(TCB) as a processing additive to control the blend morphology. The addition of TCB improved the arrangement of P3HT which resulted in good phase separated blend films. Correspondingly, the optimized solar cells showed a power conversion efficiency(PCE) of 4.17% with a fill factor(FF) of 0.69, which were higher than those of common thermal annealing devices(PCE 3.84%, FF 0.67). The efficiency was further improved to 4.74% by thermal annealing at 150 °C for 10 min with a higher FF of 0.74.     

A‐D‐A Type Small Molecules Based on Boron Dipyrromethene for Solution‐Processed Organic Solar Cells

The unique properties of boron dipyrromethene (BODIPY) dyes including facile synthesis, high absorption coefficients, and delocalized molecular orbitals as well as excellent photochemical and thermal stability, make them promising as materials for organic solar cells. Accordingly, in this study three A‐D ‐A structural small molecules of BDTT‐BODIPY, FL‐BODIPY, and TT‐BODIPY have been synthesized, in which two BODIPY acceptor units are symmetrically conjugated to 4,8‐bis(5‐(2‐ethylhexyl) thiophen‐2‐yl)benzo[1,2‐b:4,5‐b]dithiophene (BDTT), 9,9‐dioctyl‐9H‐fluorene (FL), and thieno[3,2‐b]thiophene (TT) donor cores, respectively. The manipulation of the structural parameters significantly improves the performances of the BHJ OSCs, which show power conversion efficiencies of 4.75 %, 1.51 %, and 1.67 % based on [6,6]‐phenyl C₇₁‐butyric acid methyl ester (PC₇₁BM) as the acceptor material and BDTT‐BODIPY, FL‐BODIPY, and TT‐BODIPY as the donor materials, respectively.     

Synthesis and characterization of cyclic P3HT as a donor polymer for organic solar cells

In this study, cyclic poly(3‐hexylthiophene‐2,5‐diyl) (c‐P3HT) with a controlled M_n was synthesized by the intramolecular cyclization of α‐bromo‐ω‐ethynyl‐functionalized P3HT via the Sonogashira coupling reaction. The effect of the cyclic structure, which does not have terminal groups of polymers, on the photoelectric conversion characteristics was investigated in comparison to linear P3HT (l‐P3HT). c‐P3HT was successfully synthesized with M_n ≈ 17,000, dispersity ≈ 1.2, and regioregularity ≈ 99%. The hole mobility was determined to be 5.1 × 10^?4 cm² V^?1 s^?1 by time‐of‐flight (TOF) experiment. This was comparable to that of l‐P3HT of 5.6 × 10^?4 cm² V^?1 s^?1. Organic solar cell systems were fabricated with each polymer by blending them with [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM). The l‐P3HT:PC₇₁BM system showed a dispersive TOF photocurrent profile for electron transport, whereas a nondispersive profile was observed for c‐P3HT:PC₇₁BM. In addition, an amount of collected electrons in c‐P3HT:PC₇₁BM was greater than that in l‐P3HT:PC₇₁BM for TOF experiments. The photoelectric conversion characteristics were improved by using c‐P3HT rather than l‐P3HT (power conversion efficiency [PCE] = 4.05% vs 3.23%), reflecting the nondispersive transport and the improvement of electron collection. PCEs will be much improved by applying this cyclic concept to highly‐efficient OSC polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 266–271     

Performance Enhancement of Bulk Heterojunction Solar Cells with Direct Growth of CdS‐Cluster‐Decorated Graphene Nanosheets

Two‐dimensional graphene–CdS (G–CdS) semiconductor hybrid nanosheets were synthesized in situ by graphene oxide (GO) quantum wells and a metal–xanthate precursor through a one‐step growth process. Incorporation of G–CdS nanosheets into a photoactive film consisting of poly[4,8‐bis‐(2‐ethyl‐hexyl‐thiophene‐5‐yl)‐benzo[1,2‐b:4,5‐b]dithiophene‐2,6‐diyl]‐alt‐[2‐(2‐ethyl‐hexanoyl)‐thieno[3,4‐b]thiophen‐4,6‐diyl] (PBDTTT‐C‐T) and [6,6]‐phenyl C₇₀ butyric acid methyl ester (PC₇₀BM) effectively decreases the exciton lifetime to accelerate exciton dissociation. More importantly, the decreasing energy levels of PBDTTT‐C‐T, PC₇₀BM, and G–CdS produces versatile heterojunction interfaces of PBDTTT‐C‐T:PC₇₀BM, PBDTTT‐C‐T:G–CdS, and PBDTTT‐C‐T:PC₇₀BM:G–CdS; this offers multi‐charge‐transfer channels for more efficient charge separation and transfer. The charge transfer in the blend film also depends on the G–CdS nanosheet loadings. In addition, G–CdS nanosheets improve light utilization and charge mobility in the photoactive layer. As a result, by incorporation of G–CdS nanosheets into the active layer, the power‐conversion efficiency of inverted solar cells based on PBDTTT‐C‐T and PC₇₁BM is improved from 6.0 % for a reference device without G–CdS nanosheets to 7.5 % for the device with 1.5wt % G–CdS nanosheets, due to the dramatically enhanced short‐circuit current. Combined with the advantageous mechanical properties of the PBDTTT‐C‐T:PC₇₀BM:G–CdS active layer, the novel CdS‐cluster‐decorated graphene hybrid nanomaterials provide a promising approach to improve the device performance.     

Cove‐Edge Nanoribbon Materials for Efficient Inverted Halide Perovskite Solar Cells

Two cove‐edge graphene nanoribbons hPDI2‐Pyr‐hPDI2 ( 1 ) and hPDI3‐Pyr‐hPDI3 ( 2 ) are used as efficient electron‐transporting materials (ETMs) in inverted planar perovskite solar cells (PSCs). Devices based on the new graphene nanoribbons exhibit maximum power‐conversion efficiencies (PCEs) of 15.6 % and 16.5 % for 1 and 2 , respectively, while a maximum PCE of 14.9 % is achieved with devices based on [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM). The interfacial effects induced by these new materials are studied using photoluminescence (PL), and we find that 1 and 2 act as efficient electron‐extraction materials. Additionally, compared with PC₆₁BM, these new materials are more hydrophobic and have slightly higher LUMO energy levels, thus providing better device performance and higher device stability.