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It is of significance to develop high-performance organic/inorganic hybrid thermoelectric (TE) materials for flexible cross-plane TE devices. In this work, we synthesize a flexible and free-standing sandwich-like TE film by depositing Bi2Te3 nanocrystals into a conducting porous PEDOT nanowire scaffold. The mechanically robust Bi2Te3@PEDOT nanowire film exhibits a record Seebeck coefficient of 266.4 μV K−1 with a corresponding power factor of 740.2 μW m−1 K−2 and a zT value of 0.27 at room temperature. Afterwards, we build new types of wearable cross-plane TE generator (TEG) and TE-powered temperature sensor array with a reduced number of electric leads in comparison to traditional designs. The TEG shows a maximum output power density of 3.48 μW cm−2 at a temperature difference of 17.8 K (predicted output power density of 70.6 μW cm−2 at ΔT = 80 K), outperforming most of the organic and organic/inorganic based ones. The conformal TE-powered temperature sensor array exhibits high and stable thermal sensitivity with a resolution of 0.05 K. [ABSTRACT FROM AUTHOR]

Thermoelectric polymers have attracted great attention because of their unique merits including low thermal conductivity, low cost, non- or low toxicity and high mechanical flexibility. However, their thermoelectric properties particularly the Seebeck coefficient should be greatly increased for practical applications. Although dedoping and energy filtering can increase the Seebeck coefficient, they lower the conductivity because the Seebeck coefficient and conductivity are interdependent. Here, we report simultaneous enhancements in the Seebeck coefficient and conductivity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) that is the most popular thermoelectric polymer by adding ferroelectric barium titanate (BaTiO3) nanoparticles. The BaTiO3 nanoparticles can enhance the Seebeck coefficient from 23.8 to 40.7 μV K−1 and the power factor from 34.4 to 117.0 μW m−1 K−2, and the insulating BaTiO3 nanoparticles do not decrease but increase the conductivity of PEDOT:PSS. The conductivity of the continuous PEDOT:PSS phase in the composite films can be enhanced from 587 to 1552 S cm−1. The enhancement in the Seebeck coefficient is ascribed to the energy filtering of low-energy charge carriers in PEDOT:PSS due to the spontaneous electric polarization of BaTiO3, and the increase in the conductivity is attributed to the secondary doping of PEDOT:PSS related to the high dielectric constant of the BaTiO3 nanoparticles. [ABSTRACT FROM AUTHOR]

Perovskite solar cells have attracted much attention due to their high power conversion efficiency and low fabrication cost. The efficiency of the devices depends on the charge transport and charge extraction at the interface between the perovskite and electron or hole transport material. In this study, we use Kelvin probe force microscopy (KPFM) to investigate the charge carrier generation, transport, and extraction mechanism of several different structures with/without the hole/electron interlayers. It was found that the perovskite films exhibited unbalanced charge-carrier transport and extraction in the p-i-n type structure. Meanwhile, the leakage current under bias conditions can be suppressed by using a [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) capping layer. The time-resolved photoluminescence (TR-PL) results reveal that the electrons have a longer lifetime and longer diffusion length than the holes in the perovskite layer. These results suggest that the electron extraction is more efficient than the hole extraction in the planar heterojunction devices of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/perovskite/PCBM. These findings are beneficial for further optimizing the perovskite solar cells. [ABSTRACT FROM AUTHOR]

Hybrid organic–inorganic perovskite solar cells (PSCs) have attracted great interest owing to their low fabrication costs and high power conversion efficiency. Most studies have focused on the devices with methylammonium lead trihalide perovskites. Here, we explore a new perovskite with mixed organic cations and mixed halides, MA1−xFAxPbI3−yCly. MA1−xFAxPbI3−yCly films can be fabricated by annealing at a temperature of 80–110 °C. Planar heterojunction PSCs using this perovskite as the active material can exhibit a high power conversion efficiency (PCE) of up to 18.14% with short-circuit photocurrent density (Jsc) of 21.55 ± 0.55 mA cm−2, open-circuit voltage (Voc) of 1.100 ± 0.010 V, and fill factor (FF) of 0.75 ± 0.02. The PCE is much higher than those of the control devices with other commonly employed perovskites including MAPbI3, MAPbI3−yCly, MAPbI3−yBry, and MA1−xFAxPbI3. The superior performance is mainly attributed to the enhancement of Jsc, which is a result of long charge diffusion lengths due to the presence of mixed organic cations and mixed halides. In addition, there is no obvious hysteresis in the J–V curves along the forward and reverse scan directions. The formation of undesirable δ-phase perovskite that has a band gap of 2.8 eV is not observed in the MA1−xFAxPbI3−yCly films. These findings pave the way for the design of new hybrid perovskites with stronger light absorption over a wide range, lower charge recombination, and improved charge transport properties through compositional engineering. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have attracted great attention due to their high power conversion efficiencies (PCEs) and low fabrication cost. The composition of the precursor solution determines the compositions of perovskite films. Excess precursor(s) may be used in the solution for the fabrication of perovskite films. However, it is still unclear how an excess precursor like PbI2 affects the structure and properties of the perovskite layer and the photovoltaic performance of PSCs. In this work, we investigated the effect of excess PbI2 that has a large bandgap on the electronic structure and properties of perovskite films and the photophysics and photovoltaic performance of PSCs. The presence of slightly excess PbI2 can affect the crystal structure and thus shift the Fermi level of perovskites. It can increase the open-circuit voltage (Voc) and thus the PCE of PSCs. However, the presence of a large amount of excess PbI2 is detrimental to the photovoltaic performance of PSCs. It can shorten the carrier lifetime, increase the resistance of the perovskite films, and decrease the fill factor (FF) and PCE of PSCs. [ABSTRACT FROM AUTHOR]

The device lifetime of an inverted organic solar cell (IOSC) is significantly better compared to standard-architecture OSC under ambient conditions. However, various studies have shown that when an n-type oxide is used as a selective electron transport layer (ETL) in the IOSC, a reversible light-soaking treatment is required. This reversible treatment largely hampers the practicality of the device, especially in outdoor applications, in which the light-soaking time may take hours every morning. In this work, fluorinated TiOx (F-TiOx), prepared by low-temperature solution-processed chemical bath deposition technique, was used as the ETL to significantly reduce the light-soaking time for a P3HT:PCBM based IOSC. Without affecting the device efficiency, more than ten-fold reduction in light-soaking time was observed for fluorinated TiOx (F-TiOx) when compared with conventional sol -- gel TiOx. Ultraviolet photoelectron spectroscopy (UPS) and UV photoconductivity measurements were used to understand the light-soaking time reducing mechanism. From the perspective of ITO/TiOx interface, shift in work function was observed in F-TiOx due to the partial filling of its defective sites by fluorine atoms. Consequently, this process reduces its intrinsic trap state density compared to sol -- gel TiOx even before the light-soaking treatment. As a result, the trap filling action can be completed in a shorter time upon illumination, and thus significantly reduce the duration of the necessary light-soaking. [ABSTRACT FROM AUTHOR]