wangzhaowei

Fullerene-free polymer solar cell devices based on a new acceptor, H-tri-PDI that is connected by three perylene diimide (PDI) units via imide position shows a power conversation efficiency of 7.25% with a short circuit current density of 16.5 mA cm⁻². Thus H-tri-PDI molecules and the method of connecting multiple PDI units via imide position provide a reliable guide for the further development of PDI-based acceptors.

The influence of monovalent cation halide additives on the optical, excitonic, and electrical properties of CH₃NH₃PbI₃ perovskite is reported. Monovalent cation halide with similar ionic radii to Pb²⁺, including Cu⁺, Na⁺, and Ag⁺, have been added to explore the possibility of doping. Significant reduction of sub-bandgap optical absorption and lower energetic disorder along with a shift in the Fermi level of the perovskite in the presence of these cations has been observed. The bulk hole mobility of the additive-based perovskites as estimated using the space charge limited current method exhibits an increase of up to an order of magnitude compared to the pristine perovskites with a significant decrease in the activation energy. Consequentially, enhancement in the photovoltaic parameters of additive-based solar cells is achieved. An increase in open circuit voltage for AgI (≈1.02 vs 0.95 V for the pristine) and photocurrent density for NaI- and CuBr-based solar cells (≈23 vs 21 mA cm⁻² for the pristine) has been observed. This enhanced photovoltaic performance can be attributed to the formation of uniform and continuous perovskite film, better conversion, and loading of perovskite, as well as the enhancement in the bulk charge transport along with a minimization of disorder, pointing towards possible surface passivation.

Incorporation of monovalent cation halide additives improve the semiconductor behavior and photovoltaic performance of CH₃NH₃PbI₃ perovskite through the formation of uniform and continuous perovskite film, better conversion and loading of CH₃NH₃PbI_3, and possible passivation of defect states at the crystallite surfaces, as well as the enhancement in the bulk charge transport along with a minimization of disorder.

The degradation of sexithiophene cascade organic solar cells is studied. Glass–glass encapsulated devices on indium tin oxide as transparent electrode show efficiencies of 6.6% and degrade within 500 h in illuminated 38 °C/50% RH climate. Fully flexible devices with silver nanowire electrode and alumina barrier achieve 5% efficiency and degrade within 30 h due to electrode failure.

An approach to fabricate high-efficiency inverted planar perovskites solar cells using solution-processed organic small molecules hole transporting layer is reported. Devices using CH₃NH₃PbI₃ as photoactive layer and PC₆₀BM as electron transport layer show power conversion efficiencies exceeding 12% and open-circuit voltages (V_OC) higher than 1 V.

A series of anionic self-doped conjugated polyelectrolytes (CPEs) by copolymerization of a 1,4-bis(4-sulfonatobutoxy)benzene moiety with different counter monomers of thiophene, bithiophene, and terthiophene is reported. The CPEs show high conductivity of ≈10⁻⁴ S cm⁻¹ due to being self-doped in a neutral state and exhibit excellent hole transporting property in the out-of-plane direction, compared with poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS). Moreover, the CPE incorporating a less electron-donating unit from terthiophene to thiophene exhibits a higher work function and therefore, PhNa-1T incorporating thiophene shows a relatively high work function of 5.21 eV than 4.97 eV of PEDOT:PSS. This can induce a higher internal field in the solar cell device, facilitating efficient charge collection to the electrode. As a result, polymer solar cell devices incorporating the CPEs as a hole transporting layer achieve enhanced photovoltaic performances from those of the conventional PEDOT:PSS-based devices. The solar cell efficiency reaches up to 9.89%, which is among the highest values demonstrated by PCE-10-based normal-type organic solar cells.

A series of anionic self-doped conjugated polyelectrolytes is synthesized by copolymerizing dibromo-1,4-bis(4-sulfonatobutoxy)benzene with borate compounds of thiophene, bithiophene, and terthiophene (ThCPEs). Organic solar cells using ThCPEs as the hole-transporting layer show higher photovoltaic performances than the device derived from poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) because the ThCPEs exhibit better hole-transporting properties in the out-of-plane direction and higher work functions than PEDOT:PSS.

With the advances in organic photovoltaics (OPVs), the invention of model polymers with superior properties and wide applicability is of vital importance to both the academic and industrial communities. The recent inspiring advances in OPV research have included the emergence of poly(benzodithiophene-co-thieno[3,4-b]thiophene) (PBDTTT)-based materials. Through the combined efforts on PBDTTT polymers, over 10% efficiencies have been realized recently in various types of OPV devices. This review attempts to critically summarize the recent advances with respect to five well-known PBDTTT polymers and their design considerations, basic properties, photovoltaic performance, as well as device application in conventional, inverted, tandem solar cells. These PBDTTT polymers also make great contributions to the rapid advances in the field of emerging ternary blends and fullerene-free OPVs with top performances. Addtionally, new challenges in developing novel photovoltaic polymers with more superior properties are prospected. More importantly, the research of highly efficient PBDTTT-based polymers provides useful insights and builds fundamentals for new types of OPV applications with various architectures.

Well-known PBDTTT polymers are the subject of considerable attention in the field of organic photovoltaics (OPVs). These photovoltaic polymers possess excellent absorption and hole mobility and show great potential in single- or multiple-junction, ternary blend, and fullerene-free OPV devices. Owing to the integrated morphology and device efforts, over 10% efficiencies have been realized in these novel OPV devices.

Ni₃FeN nanoparticles with a particle size of ≈100 nm and a thickness of ≈9 nm are successfully synthesized by thermal ammonolysis of ultrathin NiFe-layered double hydroxide ultrathin nanosheets. The Ni₃FeN nanoparticles exhibit excellent catalytic performance and high stability in electrochemical overall water splitting.

Morphological modification using solvent vapor annealing (SVA) provides a simple and widely used fabrication option for improving the power conversion efficiencies of solution-processed bulk heterojunction (BHJ) small molecule solar cells. Previous reports on SVA have shown that this strategy influences the degree of donor/acceptor phase separation and also improves molecular donor ordering. A blend composed of a dithienopyrrole containing oligothiophene as donor (named UU07) and [6,6]-phenyl-C61-butyric acid methyl ester as acceptor is investigated with respect to SVA treatment to explore the dynamics of the BHJ evolution as a function of annealing time. A systematic study of the time dependence of morphology evolution clarifies the fundamental mechanisms behind SVA and builds the structure–property relation to the related device performance. The following two-stage mechanism is identified: Initially, as SVA time increases, donor crystallinity is improved, along with enhanced domain purity resulting in improved charge transport properties and reduced recombination losses. However, further extending SVA time results in domains that are too large and a few large donor crystallites, depleting donor component in the mixed domain. Moreover, the larger domain microstructure suffers from enhanced recombination and overall lower bulk mobility. This not only reveals the importance of precisely controlling SVA time on gaining morphological control, but also provides a path toward rational optimization of device performance.

Time-dependent morphology evolution of solution-processed small molecule solar cells during solvent vapor annealing is systematically and methodically investigated. This not only reveals the importance of precisely controlling SVA time on gaining morphological control, but also provides a path toward the rational optimization of device performance.