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The interface energetics‐modification plays an important role in improving the power conversion efficiency (PCE) among the perovskite solar cells (PSCs). Considering the low carrier mobility caused by defects in PSCs, a double‐layer modification engineering strategy is adopted to introduce the "spiderman" NOBF4 (nitrosonium tetrafluoroborate) between tin dioxide (SnO2 and perovskite layers. NO+, as the interfacial bonding layer, can passivate the oxygen vacancy in SnO2, while BF4− can optimize the defects in the bulk of perovskite. This conclusion is confirmed by theoretical calculation and transmission electron microscopy (TEM). The synergistic effect of NO+ and BF4− distinctly heightens the carrier extraction efficiency, and the PCE of PSCs is 24.04% with a fill factor (FF) of 82.98% and long‐term stability. This study underlines the effectiveness of multifunctional additives in improving interface contact and enhancing PCE of PSCs. [ABSTRACT FROM AUTHOR]

Due to its unique photoelectric properties, MXene has a wide range of potential applications. Herein, different MXene contents (0, 0.10, 0.15, 0.20, 0.25, 0.4 wt%) of SnO2–MXene nanocomposites are used as the electron transport layer. The introduction of MXene not only inhibits SnO2 agglomeration and induces the vertical growth of CsPbIBr2, but also passivates defects of the SnO2/CsPbIBr2 interface. It effectively increases the power conversion efficiency from 8.98% to 11.21%. In addition, even after 1000 h of storage with a relative humidity of more than 50% in the ambient air, the unsealed device still maintains about 92% of its initial efficiency. This strategy provides a promising way to improve the efficiency of solar cells. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2008.11.012 Byline: Pinjiang Li (a)(b), Jihuai Wu (a), Jianming Lin (a), Miaoliang Huang (a), Yunfang Huang (a), Qinghua Li (a) Keywords: Dye-sensitized solar cell; Counter electrode; Platinum; Carbon; Electrochemistry Abstract: Pt/Carbon black counter electrode for dye-sensitized solar cells (DSSCs) was prepared by reducing H.sub.2PtCl.sub.6 with NaBH.sub.4 in carbon black. The Pt/Carbon black electrode had a high electrocatalytic activity for iodide/triiodide redox reaction. Using the Pt/Carbon black counter electrode, DSSC achieved 6.72% energy conversion efficiency under one sun illumination. Pt/Carbon black electrode shows the same energy conversion efficiency and lower cost compared with Pt electrode, which makes it available in DSSCs practical applications. Author Affiliation: (a) Institute of Materials Physical Chemistry, Huaqiao University, Quanzhou, Fujian 362021, China (b) Institute of Surface Micro and NanoMaterials, Xuchang University, Xuchang 461000, China Article History: Received 11 June 2008; Revised 29 October 2008; Accepted 29 November 2008

Perovskite layer, as the origin of optical–electrical conversion of devices, plays a very important role in perovskite solar cells (PSCs). However, lots of lead cations and halogen anions defects inevitably exit in the bulk and surface of the perovskite layer. These defects, serve as nonradiative recombination centers, degrade the performance, and damage the stability of PSCs. Herein, a strategy that anion and cation defects on the interface and in the bulk of perovskites are simultaneously passivated by doping organic molecule 4‐aminomethyl tetrahydropyran (4‐AMPR) and the surface modification with 1‐chlorobutane (1‐CB) in/on the perovskite is demonstrated. The O atoms on 4‐AMPR can coordinate with the Pb vacancy and antisite Pb defects, as well as improve perovskite morphology. The volatilization of low‐boiling 1‐CB can passivate the halogen ion defects and promote the uniform nucleation of perovskite. The PSCs jointly optimized by 4‐AMPR and 1‐CB achieve a power conversion efficiency of 22.74% and retain 90.7% of the initial efficiency after storage in air environment (RH 10 ± 5%, 25 °C) for more than 1000 h. This research demonstrates a promising strategy for simultaneously mitigating anion and cation defects both in bulk and surface of perovskite layer and thus enhancing the performance and stability of the devices. [ABSTRACT FROM AUTHOR]

We present here the successful fabrication of core–shell constructed CdZnSe@ZnSe colloidal alloy quantum dots with tunable optical properties using a hot-injection method, demonstrating great potential in photovoltaic devices. Upon employment as charge extraction materials in all-inorganic perovskite solar cells, an enhanced power conversion efficiency up to 8.65% has been achieved arising from the boosted charge transfer dynamics. [ABSTRACT FROM AUTHOR]

A crucial issue faced by quantum dot solar cells (QDSC) is how to achieve a quantum dot material with high photoluminescence (PL) quantum yield and long excited state lifetime at the same time to maximize charge carrier collection efficiency. Here, we present a new type of Zn 0.9 Cd 0.1 S/ZnSe hetero-nanocrystals that have a staggered band alignment, i.e., a type-II structure by which the wave function overlap between electrons and holes is reduced, thereby leading to a significant enhancement in the PL lifetime. The resultant QD also exhibits a QY up to 75.4%, which is, to the best of our knowledge, the highest one for a type-II QD to date. In particular, we explore the underlying relationship between the broad tunability and energy level alignment of these hetero-nanocrystals, and we highlight the properties that have delivered QDSCs and light-emitting diodes. [ABSTRACT FROM AUTHOR]

Novel and less toxic quantum dot (QD) semiconductors are desired for developing environmentally benign colloidal quantum dot solar cells. Here, the synthesis of novel lead/cadmium-free neodymium chalcogenide Nd2(S, Se, Te)3 QDs via solution-processed method is reported for the first time. The results show that small-bandgap semiconductor QDs with a narrow size distribution ranging from 2 to 8 nm can be produced, and the wide absorption band can be achieved by the redshift owing to the size quantization effect by controlling the initial loading of chalcogenide precursors. By analyzing the band structure of QDs and the energy level alignment between QDs and TiO2, the influence of energy offset between the conduction band edges of QDs and TiO2 on the charge transfer dynamics and photovoltaic performance of QD solar cells (QDSCs) is investigated. It is revealed that among the three types of QDs studied, Nd2Se3 QDSCs with the smallest energy offset exhibit the best performances and a decent power conversion efficiency of 3.19% is achieved. This work clearly demonstrates the promising potentials of novel rare earth chalcogenide quantum dots in photovoltaic applications. [ABSTRACT FROM AUTHOR]

Abstract: Polypyrrole (PPy) nanoparticle was synthesized and coated on a conducting FTO glass to construct PPy counter electrode used in dye-sensitized solar cell (DSSC). Scanning electron microscope images show that PPy with porous and particle diameter in 40–60nm is covered on the FTO glass uniformly and tightly. Cyclic voltammograms of I2/I− system measurement reveals that the PPy electrode has smaller charge-transfer resistance and higher electrocatalytic activity for the I2/I− redox reaction than that Pt electrode does. Overall energy conversion efficiency of the DSSC with the PPy counter electrode reaches 7.66%, which is higher (11%) than that of the DSSC with Pt counter electrode. The excellent photoelectric properties, simple preparation procedure and inexpensive cost allow the PPy electrode to be a credible alternative used in DSSCs. [Copyright &y& Elsevier]

Interface engineering has become the mainstream for improving the performance of perovskite solar cells (PSCs). Interfacial dipole (ID) molecules have emerged as a feasible and effective strategy to alleviate the charge carrier loss and energy loss in PSCs. Here, the three symmetrical donor–acceptor interfacial dipole molecules (named PzT, PzTE, and PzTN) are designed and synthesized with identical hole transport backbone and different anchoring groups. The ID molecule is introduced into the interface between the perovskite layer and the hole transport layer. The dipole moments of ID molecules regulate the surface work function and energy‐level alignment of perovskites, improve charge extraction, and reduce energy loss at the interface. Meanwhile, the anchoring groups of ID molecules coordinate with the defects on the surface of PVK and HTL, reduce interfacial trap state density and charge accumulation, and mitigate the carrier non‐radiative recombination losses. As a result, PzTN‐modified PSC achieved a champion power conversion efficiency of 25.34% with a photovoltage of 1.176 V and a fill factor (FF) of 83.27%, accompanied by almost undetectable hysteresis and excellent operating stability. This research demonstrates a feasible strategy for efficient and stable PSCs by interfacial dipole molecules. [ABSTRACT FROM AUTHOR]

Two N-heteroacene small molecules, P2BT and P2B2 T, with 2,1,3-benzodiathiazole end-capped N-heteroacene unit as the central building block have been designed and synthesized for bulk-heterojunction solar cells. Single-junction devices based on P2B2 T:PC 71 BM have achieved an impressive power conversion efficiency of 7.16% without any special treatment, which is the record efficiency among the N-heteroacene-based photovoltaics. [ABSTRACT FROM AUTHOR]

• • Formamidinium lead halide perovskite quantum dots have been fabricated. • • The charge extraction and transfer at perovskite/carbon interface is accelerated. • • The device yields an enhanced efficiency of 8.55% under one standard solar irradiation. • • The performances are nearly unchanged after storage for 60 days in air atmosphere. Rapid charge extraction and transfer is a crucial prerequisite to achieve high-performance perovskite solar cells, however, the notorious non-radiative recombination pathways limit the further efficiency enhancement owing to the energy barriers between charge transporting layers and perovskite layers. Aiming to realize the accelerated charge extraction and reduced charge loss, in the current work, formamidinium lead halide (FAPbX 3 , X = Cl, Br, or I) perovskite nanocrystals are successfully fabricated using high-melting-point ligands to modify the perovskite/carbon interface in all-inorganic CsPbBr 3 perovskite solar cells, which are regarded as promising photovoltaic device because of their superior stability under rigorous conditions comparing to organic-inorganic hybrid perovskite solar cells. By optimizing the composition of FAPbX 3 perovskite nanocrystals, an elevated power conversion efficiency up to 8.55% is achieved owing to the enhanced charge transfer kinetics and reduced charge recombination loss, demonstrating the importance of interface control in high-performance photovoltaic platforms. [ABSTRACT FROM AUTHOR]

The severe interface charge recombination caused by the large energy difference between perovskite material and carbon electrode significantly limits the further performance improvement of the all-inorganic perovskite solar cells (PSCs). We apply innovatively multilayer of quaternary Ag-In-Ga-S (AIGS) quantum dots (QDs) with cascade-like valence bands as hole-transport materials to assemble all-inorganic PSCs, and the resultant all-inorganic PSCs exhibit a power conversion efficiency (PCE) of 8.46%, which is enhanced by 20.9% in comparison with 7% for the pristine device. The high performance of the PSCs indicates that sequential layers of AIGS QDs with cascade-like energy levels can facilitate the charge separation, reduce the barrier the holes crossing and suppress the charge recombination. Stack of QDs with cascade-like energy levels provide solution-processed PSCs with a new method to enhance device performance. [ABSTRACT FROM AUTHOR]

Polymer gel electrolytes having super catalytic behaviors and robust Pt-free counter electrodes (CEs) are promising for high-efficiency and cost-effective quasi-solid-state dye-sensitized solar cells (DSSCs). We present here the molecular design of polyaniline (polypyrrole)-graphene complex for conducting gel electrolytes and CEs, aiming at reducing their charge-transfer resistance and enhancing catalytic activity. The quasi-solid-stated DSSCs tailored with polyaniline-carbon nanotube and polypyrrole-carbon nanotube complexes yield maximized power conversion efficiencies of 8.23% and 7.69%, respectively. Arising from good encapsulation of three-dimension gel matrix, the photovoltaics are featured with relatively good long-term stability over 15 days. The high-efficiency and reasonable durability make so-called conducting gel electrolytes and Pt-free CEs promising in enhancing comprehensive properties of quasi-solid-state DSSC platforms. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) lifetime of the D-A polymer can ensure that there is enough time for the exciton to reach the interface of donor-acceptor and separate it into free charges. Also, the introduction of electrons withdrawing groups in D-A polymer can effectively adjust the band gap, molecular self-assembly, electron mobility, fluorescence lifetime, and optoelectronic properties. Herein, we use 2,1,3-benzothiadiazole (BT) as an acceptor unit, and indole and benzodithiophene (BDT) as the electron acceptors in the D-A copolymers with different proportions of BT and indole. The ratio of the monomers affect not only the electrochemical structure but also the PL lifetime. Results show that the PL lifetime is obviously changed with the increase of BT. The polymer, possessing a long PL lifetime and outstanding charge transfer capability, exhibits a high power conversion efficiency of hybrid solar cells. [ABSTRACT FROM AUTHOR]

A facile, low-cost and low-temperature fabrication approach of counter electrode is essential for pursuing robust photovoltaic devices. Herein, we develop a hydrothermal in situ growth of Cobalt–Ruthenium (Co–Ru) alloy nanofiber electrode for quantum dot solar cell (QDSC) applications. Colloidal CdS QDs with tunable absorption band edge are synthesized and used as light absorber. After optimizing the QDs with the highest photoluminescence quantum yield accompanied by considerable solar light absorption ability, QDSC based on Co–Ru alloy electrode delivers a much higher power conversion efficiency than its counterparts, i.e., either pure Co or Ru metal electrodes. In detail, Co–Ru alloy electrode exhibits high specific area, excellent electrical behavior, intimate interface contact, and good stability, thus leading to notable improved device performances. The impressive robust function of Co–Ru alloy with simple manufacturing procedure highlights its potential applications in robust QDSCs. [ABSTRACT FROM AUTHOR]

Solution-processed organic/inorganic hybrid solar cells have emerged as a new platform for low-cost optoelectronics. At the heart of photovoltaic devices lies the matching of a junction, which requires the suitable energy level alignment of n-type and p-type semiconductors. Incorporating foreign ions into bulk semiconductors has been largely employed for many decades, yet electronically active doping in energy level control of the hybrid bulk heterojunctions has been rarely involved and the demonstration of robust functional optoelectronic devices had thus far been elusive. Herein, we introduce Ru ions into TiO 2 to decorate the energy level of the acceptor to gain better energy level alignment between the donor and acceptor. By reducing the ‘excess’ energy offset between the n-type and p-type semiconductors, the electron transfer becomes faster, thus leading to a notable enhancement in power conversion efficiency, i.e., from 2.20% to 2.89%. The results demonstrate that the energy level can be controlled effectively by the versatile Ru dopants. This work opens an effective route for accelerating the charge carrier transfer at the interface and achieving high-performance organic/inorganic hybrid optoelectronic devices. [ABSTRACT FROM AUTHOR]

A novel titanium foil substrate strategy for the synthesis of high electrocatalytic activity nickel sulfide/polyaniline/titanium (NiS/PANI/Ti) composite film with one-dimensional (1D) net-work structure by using an in situ electropolymerization route, and proposed as platinum (Pt)-free counter electrode (CE) catalyst for flexible dye-sensitized solar cells (FDSSCs). The photovoltaic performance of the FDSSC based on the NiS/PANI/Ti CE exhibits Jsc of 14.56 mA · cm −2 , Voc of 0.743 V, FF of 0.68, and corresponding to the η of 7.35%, much higher photoelectric conversion efficiency than that of Pt/Ti CE (6.24%). The NiS/PANI/Ti CE with 1D net-work structure is characterized by using the scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization plots. The NiS/PANI/Ti CE presents multiple functions, i.e., excellent conductivity, great electrocatalytic ability for iodine/triiodine, and lower charge transfer resistance of 1.48 ± 0.02 Ω · cm 2 compared to the Pt/Ti electrode (2.25 ± 0.02 Ω · cm 2 ). The photocurrent-photovoltage ( J-V ) character curves are further used to calculate theoretical short-current densities and open-circuit voltage of the devices. Therefore, the NiS/PANI/Ti CE with 1D net-work structure can be considered as a promising and efficient CE for FDSSCs. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we study hybrid solar cells based on blends of the semiconducting polymer poly(3-octylthiophene-2,5-diyl)(P3OT) and [6,6]-phenyl C61 butyric acid methyl (PCBM) coated titanium dioxide (TiO2) nanocrystal film. The Fourier transform infrared spectra (FTIR), UV–vis absorption spectra and PL quenching researches show that the films had a stronger absorption in visible light range. The influence of the PCBM:P3OT ratio were researched and the optimized ratio of PCBM to P3OT (1:1.5) exhibit a short circuit current of 4.42mAcm−2, an open circuit voltage of 0.81V, a fill factor of 0.73 and a light-to-electric conversion efficiency of 2.61% under a simulated solar light irradiation of 100mWcm−2. [Copyright &y& Elsevier]

Abstract: A poly(methyl methacrylate-co-methacrylate acid)/poly(ethylene glycol) [P(MMA-co-MAA)/PEG] polyblend with viscoelasticity was synthesized by a copolymerizing reaction between methyl methacrylate (MMA) and methacrylate acid (MAA) using azobisisobutyronitrile (AIBN) as initiator in poly(ethylene glycol) (PEG) methanol solution. Then, a polyblend gel electrolyte was prepared by adding KI and I 2 to P(MMA-co-MAA)/PEG system. The influence of compositions of the polyblend gel electrolyte on the ionic conductivity and the effect of temperature on photoelectronic performance of quasi-solid state dye-sensitized solar cell (QS-DSSC) were discussed. It was found that the polyblend gel electrolyte was a good candidate as high-temperature electrolyte for QS-DSSCs. Under an optimized condition, the highest conductivity of the polyblend gel electrolyte was 2.70mS/cm2 at 30°C. Based on the polyblend gel electrolyte, a light-to-electricity conversion efficiency of 4.85% for QS-DSSC was achieved under AM 1.5 simulated solar light illumination at 60°C. [Copyright &y& Elsevier]