RESUMEN
Defects, inevitably produced within bulk and at perovskite-transport layer interfaces (PTLIs), are detrimental to power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). It is demonstrated that a crosslinkable organic small molecule thioctic acid (TA), which can simultaneously be chemically anchored to the surface of TiO2 and methylammonium lead iodide (MAPbI3 ) through coordination effects and then in situ crosslinked to form a robust continuous polymer (Poly(TA)) network after thermal treatment, can be introduced into PSCs as a new bifacial passivation agent for greatly passivating the defects. It is also discovered that Poly(TA) can additionally enhance the charge extraction efficiency and the water-resisting and light-resisting abilities of perovskite film. These newly discovered features of Poly(TA) make PSCs herein achieve among the best PCE of 20.4% ever reported for MAPbI3 with negligible hysteresis, along with much enhanced ultraviolet, air, and operational stabilities. Density functional theory calculations reveal that the passivation of MAPbI3 bulk and PTLIs by Poly(TA) occurs through the interaction of functional groups (COOH, CS) in Poly(TA) with under-coordinated Pb2+ in MAPbI3 and Ti4+ in TiO2 , which is supported by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.
RESUMEN
Minimization of defects and ion migration in organic-inorganic lead halide perovskite films is desirable for obtaining photovoltaic devices with high power conversion efficiency (PCE) and long-term stability. However, achieving this target is still a challenge due to the lack of efficient multifunctional passivators. Herein, to address this issue, n-type goethite (FeOOH) quantum dots (QDs) are introduced into the perovskite light-absorption layer for achieving efficient and stable perovskite solar cells (PSCs). It is found that the iron, oxygen, and hydroxyl of FeOOH QDs can interact with iodine, lead, and methylamine, respectively. As a result, the crystallization kinetics process can be retarded, thereby resulting in high quality perovskite films with large grain size. Meanwhile, the trap states of perovskite can be effectively passivated via interaction with the under-coordinated metal (Pb) cations, halide (I) anions on the perovskite crystal surface. Consequently, the PSCs with FeOOH QDs achieve a high efficiency close to 20% with negligible hysteresis. Most strikingly, the long-term stability of PSCs is significantly enhanced. Furthermore, compared with the CH3 NH3 PbI3 -based device, a higher PCE of 21.0% is achieved for the device assembled with a Cs0.05 FA0.81 MA0.14 PbBr0.45 I2.55 perovskite layer.
RESUMEN
The quality of perovskite films is a crucial factor governing the photovoltaic performance of perovskite solar cells. However, perovskite films fabricated by the conventional one-step spin-coating procedure are far from ideal due to uncontrollable crystal growth. Herein, we report a facile recrystallization procedure using a thiazole additive coupled with vapor annealing to simultaneously modulate the perovskite crystal growth and suppress the surface defects. High quality perovskite films with no pin holes, high crystallinity, large grain size, and low roughness were obtained. Moreover, using the space charge limited current method, we observe that the defect density of the as-prepared perovskite films with the thiazole additive was decreased by 40% when compared with the film without thiazole. The lower defect density of these perovskite films enables the achievement of a final power conversion efficiency of 18% and an exceptionally high fill factor of 0.82, which correspond to a 25% enhancement compared with the control device. Our results reveal a novel and facile path to modulate the perovskite crystal growth and simultaneously suppress the film defect density and increasing efficiency in perovskite photovoltaics and related optoelectronic applications.
RESUMEN
The carbon nanotube aerogel (CNA) with an ultra-low density, three-dimensional network nanostructure, superior electronic conductivity and large surface area is being widely employed as a catalytic electrode and catalytic support. Impressively, dye-sensitized solar cells (DSSCs) assembled with a CNA counter electrode (CE) achieved a maximum power conversion efficiency (PCE) of 8.28%, which exceeded that of the conventional platinum (Pt)-based DSSC (7.20%) under the same conditions. Furthermore, highly dispersed CoS2 nanoparticles endowed with excellent intrinsic catalytic activity were hydrothermally incorporated to form a CNA-supported CoS2 (CNA-CoS2) CE, which was due to the large number of catalytically active sites and sufficient connections between CoS2 and the CNA. The electrocatalytic ability and stability were systematically evaluated by cyclic voltammetry (CV), electrochemical impedance spectra (EIS) and Tafel polarization, which confirmed that the resultant CNA-CoS2 hybrid CE exhibited a remarkably higher electrocatalytic activity toward I3- reduction, and faster ion diffusion and electron transfer than the pure CNA CE. Such cost-effective DSSCs assembled with an optimized CNA-CoS2 CE yielded an enhanced PCE of 8.92%, comparable to that of the cell fabricated with the CNA-Pt hybrid CE reported in our published literature (9.04%). These results indicate that the CNA-CoS2 CE can be considered as a promising candidate for Pt-free CEs used in low-cost and high-performance DSSCs.
RESUMEN
An excellent ternary composite photocatalyst consisting of silver orthophosphate (Ag3PO4), attapulgite (ATP), and TiO2 was synthesized, in which heterojunction was formed between dissimilar semiconductors to promote the separation of photo-generated charges. The ATP/TiO2/Ag3PO4 composite was characterized by SEM, XRD, and UV-vis diffuse reflectance spectroscopy. The co-deposition of Ag3PO4 and TiO2 nanoparticles onto the surface of ATP forms a lath-particle structure. Compared with composite photocatalysts consisting of two phases, ATP/TiO2/Ag3PO4 ternary composite exhibits greatly improved photocatalytic activity for degradation of rhodamine B under simulated solar irradiation. Such ternary composite not only improves the stability of Ag3PO4, but also lowers the cost by reducing application amount of Ag3PO4, which provides guidance for the design of Ag3PO4- and Ag-based composites for photocatalytic applications.
RESUMEN
Thermoelectric NaCo2 O4 /TiO2 coaxial nanofibers are prepared and distributed in the perovskite solar cells. Under illumination, p-type NaCo2 O4 can convert unwanted heat to thermal voltage, and thus promote the electron extraction and transport with the action of electrostatic force. These advantages collectively contribute to an overall power conversion efficiency improvement of ≈20% (15.14% vs 12.65%).
RESUMEN
Nb-doped SrTiO3 ceramics doped with the surface modification of nanosized titania was prepared via liquid phase deposition approach and subsequent sintered in an Ar atmosphere. The surface modification of nanosized titania significantly improved the ratio of the electrical conductivity to thermal conductivity of SrTiO3 ceramic doped with Nb, and has little impact on the Seebeck coefficient, thus obviously improving the dimensionless thermoelectric figure of merit (ZT value). The surface modification of nanosized titania is a much better method to lower the thermal conductivity and to enhance the electrical conductivity than the mechanical mixing process of nanosized titania. The highest ZT value of 0.33 at 900 K was obtained. The reason for the improved thermoelectric performances by the surface modification of nano-sized titania was preliminary investigated.
RESUMEN
Organometal halide perovskite (CH3NH3PbI3) could be crystallized by exposing PbI2 to either CH3NH3I solution or CH3NH3I vapor. Though high performance was achieved in both approaches, it was still not clear which approach would be more desirable for device performance in principle. Herein, we addressed this issue by investigating the influence of crystallization condition on perovskite morphology, and subsequently on device performances. We found that vapor-crystallized perovskite devices demonstrated smoother surface morphology, better light absorption, lower charge recombination, and thus much higher conversion efficiency than solution-crystallized devices, which would give some useful enlightenment to develop high-performance planar perovskite solar cells.
RESUMEN
Authors reported an effective path to increase the electrical conductivity while to decrease the thermal conductivity, and thus to enhance the ZT value by nano-inclusions. By this method, the ZT value of Nb-doped SrTiO3 was enhanced 9-fold by yttria stabilized zirconia (YSZ) nano-inclusions. YSZ inclusions, located inside grain and in triple junction, can reduce the thermal conductivity by effective interface phonon scattering, enhance the electrical conductivity by promoting the abnormal grain growth, and thus lead to the obvious enhancement of ZT value, which strongly suggests that, it is possible to not only reduce the thermal conductivity, but also increase the electrical conductivity by nano-inclusions with low thermal conductivity. This study will give some useful enlightenment to the preparation of high-performance oxide thermoelectric materials.