Improved interfacial property by small molecule ethanediamine for high performance inverted planar perovskite solar cells

We report a simple and effective method to realize desirable interfacial property for inverted planar perovskite solar cells(PSCs)by using small molecule ethanediamine for the construction of a novel polyelectrolyte hole transport material(P3CT-ED HTM).It is found that P3CT-ED can not only improve the hole transport property of P3CT-K but also improve the crystallinity of adjacent perovskite film.In addition,the introduction of ethanediamine into P3CT realigns the conduction and valence bands upwards,passivates surface defects and reduces nonradiative recombination.As a consequence,compared to P3CT-K hole transport layer(HTL)based devices,the average power conversion efficiency(PCE)is boosted from17.2% to 19.6% for the counterparts with P3CT-ED,with simultaneous enhancement in open circuit voltage and fill factor.The resultant device displays a champion PCE of 20.5% with negligible hysteresis.     

Recent progress of hybrid cathode interface layer for organic solar cells

Organic solar cells(OSCs) have gained conspicuous progress during the past few decades due to the development of materials and upgrading of the device structure. The power conversion efficiency(PCE) of the single-junction device had surpassed 19%. The cathode interface layer(CIL), by optimizing the connection between the active layer and the cathode electrode, has become a momentous part to strengthen the performances of the OSCs. Simultaneously, CIL is also indispensable to illustrating the wor...     

Heating induced aggregation in non-fullerene organic solar cells towards high performance

Molecular ordering within the photoactive layer plays a crucial role in determining the device performance of organic solar cells(OSCs).However,the simultaneous molecular ordering processes of polymer donors and non-fullerene acceptors(NFAs)during solution casting usually bring confinement effect,leading to insufficient structural order of photovoltaic components.Herein,the molecular packing of mINPOIC NFA is effectively formed through a heating induced aggregation strategy,with the aggregation of PBDB-T,which has a strong temperature dependence,is retarded by casting on a preheated substrate to reduce its interference toward m-INPOIC.A sequent thermal annealing treatment is then applied to promote the ordering of PBDB-T and achieve balanced aggregation of both donors and acceptors,resulting in the achievement of a maximum efficiency of 13.9% of PBDB-T:m-INPOIC binary OSCs.This work disentangles the interactions of donor polymer and NFA during the solution casting process and develops a rational strategy to enhance the molecular packing of NFAs to boost device performance.     

Mesoporous carbon material as cathode for high performance lithium-ion capacitor

The mesoporous carbon material with large pore volume and high surface area by a simple situ MgO template method is synthesized, which is utilized as cathode to assemble a high performance lithium ion capacitor.     

Development of small-molecule materials for high-performance organic solar cells

With the rapid development in recent years, small-molecule organic solar cell is challenging the dominance of its counterpart, polymer solar cell. The top power conversion efficiencies of both single and tandem solar cells based on small molecules have surpassed 9%. In this mini review, achievements of small molecules with impressive photovoltaic performance especially reported in the last two years were highlighted. The relationship between molecular structure and device performance was analyzed, which draws some rules for rational molecular design. Five series of p- and n-type small molecules were selected based on the consideration of their competitiveness of power conversion efficiencies.     

Progress of the key materials for organic solar cells

Organic solar cells have attracted academic and industrial interests due to the advantages like lightweight, flexibility and roll-to-roll fabrication. Nowadays, 18% power conversion efficiency has been achieved in the state-of-the-art organic solar cells. The recent rapid progress in organic solar cells relies on the continuously emerging new materials and device fabrication technologies, and the deep understanding on film morphology, molecular packing and device physics. Donor and acceptor materials are the key materials for organic solar cells since they determine the device performance. The past 25 years have witnessed an odyssey in developing high-performance donors and acceptors. In this review, we focus on those star materials and milestone work, and introduce the molecular structure evolution of key materials. These key materials include homopolymer donors, D-A copolymer donors, A-D-A small molecular donors, fullerene acceptors and nonfullerene acceptors. At last, we outlook the challenges and very important directions in key materials development.     

Naphthodithiophene-based donor materials for solution processed organic solar cells

As an emerging donor building block, naphthodithiophene (NDT) is causing more concerns in the field of organic semiconductors. With the rigid and coplanar molecule structure, NDT will exhibit more application space relying on its own advantage for facilitating the charge carrier transport. In this review article, we have summarized the development progress on the NDT-based donor materials for solution processed organic solar cells. Discussions and comments on those representative NDT type materials about structure and property are also presented.     

Incremental optimization in donor polymers for bulk heterojunction organic solar cells exhibiting high performance

The power conversion efficiency of an organic solar cell has now exceeded the 10% mark, which is a significant improvement in the last decade. This has been made possible due to the development of low-band-gap polymers with tunable electron affinity, ionization potential, solubility, and miscibility with the fullerene acceptor, and the improved understanding of the factors affecting the critical device parameters such as the V_OC and the J_SC. This review examines the latest strategies, results, and trends that have evolved in the design of solar cells with better efficiency and durability. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

The evolution of organic materials for efficient dye-sensitized solar cells

In the past three decades, dye-sensitized solar cells (DSSCs) have gained increased recognition as a potential substitute for inexpensive photovoltaic (PV) devices, and their maximum efficiency has grown from 7% to 14.3%. Recent developments in DSSCs have attracted a plethora of research activities geared at realizing their full potential. DSSCs have seen a revival as the finest technology for specific applications with unique features such as low-cost, non-toxic, colourful, transparent, ease of fabrication, flexibility, and efficient indoor light operation. Several organic materials are being explored and employed in DSSCs to enhance their performance, robustness, and lower production costs to be viable alternatives in the solar cell markets. This review provides a concise summary of the developments in the field over the past decade, with a special focus on the incorporation of organic materials into DSSCs. It covers all elements of the DSSC technology, including practical approaches and novel materials. Finally, the emerging applications of DSSCs, and their future promise are also discussed.     

A random copolymer based on dithienothiophene and diketopyrrolopyrrole units for high performance organic solar cells

A random donor-acceptor semiconducting copolymer based on diketopyrrolopyrrole as the acceptor unit and dithienothiophene as the donor unit has been synthesized and characterized. Preliminary studies of BHJ solar cells based on this polymer with PC(71)BM showed a high PCE of above 5% under 100 mW cm(-2) AM1.5 solar illumination.     

Modulating morphology via side-chain engineering of fused ring electron acceptors for high performance organic solar cells

In this work, four fused ring electron acceptors(FREAs), 2F-C5, 2F-C6, 2F-C8 and 2F-C10, are developed to investigate the effect of side-chain size on the molecular properties and photovoltaic performance of FREA systematically. The elongation of side-chains in the FREAs not only improves their solubility in the processing solvent, but also enhances their miscibility with the donor PBDB-T. It helps the FREA diffuse into the donor PBDB-T during film-formation, thus leading to the decrease in domain size and domain purity from PBDB-T:2F-C5 to PBDB-T:2F-C10 blend films in sequence. The smaller domain size affords more D/A interfaces to benefit exciton dissociation and inhibit monomolecular recombination. However, severe bimolecular recombination occurs when the domain purity decreases to a critical point. Due to the dual function of the increment of side-chain length, both short-circuit current density(J_(SC)) and fill factor(FF) of devices exhibit an evolution of first increasing then decreasing from 2F-C5, 2F-C6, 2F-C8 to 2F-C10 based OSCs. The PBDB-T:2F-C8 based OSCs get a fine balance in morphology with moderate domain size as well as high domain purity simultaneously for the least charge carrier recombination, thus achieving the highest power conversion efficiency of 12.28% with the best J_(SC)(21.27 mA cm~(-2)) and FF(71.96%).     

Latest progress on fully non-fused electron acceptors for high-performance organic solar cells

Benefitting from the development of non-fullerene acceptors(NFAs), remarkable advances have been achieved with the power conversion efficiency(PCE) exceeding 19% over the last few years. However, the major achievement comes from fused ring electron acceptors(FREAs) with complex structures, leading to high cost. Hence, it is urgent to design new materials to resolve the cost issues concerning basic commercial requirements of organic solar cells. Recently, great progress has been made in fully non...     

Fullerene derivative acceptors for high performance polymer solar cells

Polymer solar cells (PSCs) are composed of a blend film of a conjugated polymer donor and a soluble fullerene derivative acceptor sandwiched between a PEDOT?:?PSS coated ITO positive electrode and a low workfunction metal negative electrode. The conjugated polymer donor and the fullerene derivative acceptor are the key photovoltaic materials for high performance PSCs. For the acceptors, although [6,6]-phenyl-C(61)-butyric acid methyl ester (PC(60)BM) and its corresponding C(70) derivative PC(70)BM are dominantly used as the acceptors in PSC at present, several series of new fullerene derivatives with higher-lying LUMO energy level and better solubility were reported in recent years for further improving the power conversion efficiency of the PSCs. In this perspective paper, we reviewed the recent research progress on the new fullerene derivative acceptors, including various PC(60)BM-like C(60) derivatives, PC(60)BM bisadduct, PC(70)BM bisadduct, indene-C(60) bisadduct and indene-C(70) bisadduct, trimetallic nitride endohedral fullerenes and other C(60) derivatives with multi side chains. The synthesis and physicochemical properties of PC(60)BM and PC(70)BM were also introduced considering the importance of the two fullerene acceptors.     

Single-wall carbon nanotube-based proton exchange membrane assembly for hydrogen fuel cells

A membrane electrode assembly (MEA) for hydrogen fuel cells has been fabricated using single-walled carbon nanotubes (SWCNTs) support and platinum catalyst. Films of SWCNTs and commercial platinum (Pt) black were sequentially cast on a carbon fiber electrode (CFE) using a simple electrophoretic deposition procedure. Scanning electron microscopy and Raman spectroscopy showed that the nanotubes and the platinum retained their nanostructure morphology on the carbon fiber surface. Electrochemical impedance spectroscopy (EIS) revealed that the carbon nanotube-based electrodes exhibited an order of magnitude lower charge-transfer reaction resistance (R(ct)) for the hydrogen evolution reaction (HER) than did the commercial carbon black (CB)-based electrodes. The proton exchange membrane (PEM) assembly fabricated using the CFE/SWCNT/Pt electrodes was evaluated using a fuel cell testing unit operating with H(2) and O(2) as input fuels at 25 and 60 degrees C. The maximum power density obtained using CFE/SWCNT/Pt electrodes as both the anode and the cathode was approximately 20% better than that using the CFE/CB/Pt electrodes.     

Inorganic p-type semiconductors and carbon materials based hole transport materials for perovskite solar cells

Incorporation of proper inorganic p-type semiconductors as hole transport layer has great potential to increase long-term stability while maintaining high power conversion efficiency of perovskite solar cells with low material cost.     

Material structure-composite morphology-photovoltaic performance relationship for organic bulk heterojunction solar cells

Conjugated PPV-PPE copolymer has been investigated in organic solar cells in combination with twelve different fullerene derivatives. It was shown that the length of solubilizing alkyl chains in the fullerene derivative structures correlates well with the performance of photovoltaic cells.     

D-A structural protean small molecule donor materials for solution-processed organic solar cells

This review summarizes the high performance small molecule donors of organic solar cells in various classes of typical donor-acceptor (D-A) structures and discusses their relationships briefly.     

Self-doped n-type small molecular electron transport materials for high-performance organic solar cells

Two naphthalene diimide (NDI) and perylene diimide (PDI) based n-type water/alcohol soluble small molecules (NFN and PFP) are designed and utilized as electron transport layers (ETLs) for organic solar cells (OSCs). NFN and PFP are synthesized by using Sonogashira coupling from alkynyl modified fluorene with mono-bromo substituted NDI and PDI. Density functional theory study results of NFN and PFP show that they possess excellent planarity due to the employment of triple bonds as connection units. Moreover, it was shown by electron paramagnetic resonance study that both NFN and PFP possess obvious self-doping behaviors, which may effectively enhance their charge transporting capability as ETLs in OSCs. Power conversion efficiencies of 8.59% and 9.80% can be achieved for OSCs with NFN and PFP as ETLs, respectively. The higher power conversion efficiency (PCE) of PFP based photovoltaic device is originated from the stronger doping property and higher mobility of PFP.     

Thieno[3,4-c]pyrrole-4,6-dione based copolymers for high performance organic solar cells and organic field effect transistors

Donor-acceptor type copolymers have wide applications in organic field-effect transistors and organic photovoltaic devices. Thieno[3,4-c]pyrrole-4,6-dione (TPD), as an electron-withdrawing unit, has been widely used in D-A type copolymers recently. Till now, the highest power conversion efficiency and mobility of TPD-based copolymers are over 8% and 1.0 cm² V^-1 s^-1 respectively. In this review, the recent progress of TPD-based copolymers in organic solar cells and organic transistors is summarized.