Molecularly Engineered Hole Transporting Materials for High Performance Perovskite Solar Cells

Perovskite solar cells have rapidly revolutionized the photovoltaic research showing an im-pressively dynamic progress on power conversion efficiency from 3.8 to 22% in only several years, a record for a nascent technology. Furthermore, inexpensive precursors and simple fabrication methods of perovskite materials hold a great potential for future low-cost energy generation enabling the global transition to a low-carbon society. The best performing device configuration of perovskite solar cell is composed of an electron transporting material, typi-cally a mesoporous layer of titanium dioxide, which is infiltrated with perovskite material and coated with a hole transporting material. However, although perovskite solar cells have achieved high power conversion efficiency values, there are several challenges limiting the industrial realization of low-cost, stable, and high-efficiency photovoltaic devices. To date, spiro-OMeTAD and PTAA are hole transporting materials of choice in order to main-tain the highest efficiency, however, the prohibitively high price hinders progress towards cheap perovskite solar cell manufacturing and may contribute to more than 30% of the overall module cost. Additionally, such wide bandgap hole transporting materials typically require doping in order to match necessary electrical conductivity and the use of additives is prob-lematic, since hygroscopic nature of doping makes the hole transporting layer highly hydro-philic leading to rapid degradation, negatively influencing the stability of the entire device. In order to overcome these problems, the rational design, synthesis, and characterization of a variety of small molecule-based hole transporting materials have been on a focus of this the-sis. Through judicious molecular engineering four innovative hole transporting materials KR131, KR216, KR374, and DDOF were developed via alternative synthetic schemes with the minimized number of steps and simple workup procedures allowing cost-effective upscale. Employing various characterization methods, the relationship between the molecular struc-ture of the novel hole transporting materials and performance of perovskite solar cells was investigated, leading to a fundamental understanding of the requirements of the hole trans-porting materials and further improvement of the photovoltaic performance. Furthermore, the synthesis of the dopant-free hole transporting materials based on push-pull architecture is presented. Highly ordered characteristic face-on organization of KR321 hole transporting molecules benefits to increased vertical charge carrier transport within a perov-skite solar cell, leading to a power conversion efficiency over 19% with improved durability. The obtained result using pristine hole transporting material is the highest and outperforms most of the other dopant-free hole transporting materials reported to date. Highly hydropho-bic nature of KR321 may serve as a protection of perovskite layer from the moisture and pre-vent the diffusion of external moieties, showing a promising avenue to stabilize perovskite solar cells

Efficiency vs. stability: dopant-free hole transporting materials towards stabilized perovskite solar cells

In the last decade, perovskite solar cells have been considered a promising and burgeoning technology for solar energy conversion with a power conversion efficiency currently exceeding 24%. However, although perovskite solar cells have achieved high power conversion efficiency, there are still several challenges limiting their industrial realization. The actual bottleneck for real uptake in the market still remains the cost-ineffective components and instability, to which doping-induced degradation of charge selective layers may contribute significantly. This article overviews the highest performance molecular and polymeric doped and dopant-free HTMs, showing how small changes in the molecular structure such as different atoms and different functional groups and changes in substitution positions or the length of the pi-conjugated systems can affect photovoltaic performance and long-term stability of perovskite solar cells

In-situ cross-linkable hole transporting triazatruxene monomers for optoelectronic devicestr

The invention discloses a polymerizable triazatruxene-based compound of formula (I), an optoelectronic and/or photoelectrochemical device comprising said compound of formula (I) as hole transporting material in hole transport layer under the form of a polymer, and a method of fabrication thereof

Dispiro-​oxepine​/thiapine derivatives for optoelectronic semiconductors

The dispiro-oxepine/dispiro-thiapine derivatives for optoelectronic semiconductors is a compound based on a structure having a functionalized dispiro compound of formula (Ia) or (Ib) with the core unit being a seven-membered heterocycle oxepine or thiapine, the derivative being formed by combining (Ia) or (Ib): with two moities selected from K1 and K2: The derivative is used as a hole transporting material in an optoelectronic and/or photoelectrochemical device

Diketopyrrolopyrrole-based sensitizers for dye-sensitized solar cell applications: anchor engineering

A series of donor-chromophore-anchor (D-C-A) sensitizers comprising the diketopyrrolopyrrole (DPP) chromophore were synthesized and tested in both I-3(-)/I- and Co[(bpy)](3+/2+) redox shuttle DSC devices. The dye series was strategically designed to elucidate structure-property relationships, concerning overall performance and compatibility with these two electrolytes. Selective fluorine incorporation improved I-3(-)/I--based DSC performance, while hindering performance with the positively charged cobalt-based redox shuttle. Incorporation of a pyridine heterocycle into the DPP chromophore increased spectral breadth, but decreased performance metrics for both electrolyte systems. These results are understood through detailed electrochemical, photophysical, and computational studies

Hole transporting organic molecules containing enamine groups for optoelectronic and photoelectrochemical devices

The present invention relates to a compound of formula (I) based on enamine derivatives and used as organic hole conductors or hole transporting material in an optoelectronic or photoelectrochemical device. The present invention relates to the hole transporting compounds based on enamine derivatives for efficiency perovskite or dye sensitized solar cells and optoelectronic devices, organic light-emitting diode (OLED), field-effect transistors (FET)

Rational design of triazatruxene-based hole conductors for perovskite solar cells

Triazatruxene core based hole transporting materials (HTMs), HMDI (5,10,15-trihexyl-3,8,13-trimethoxy-10,15-dihydro-5H-diindolo[3,2-a: 3',2'-c]carbazole) and HPDI (5,10,15-tris(4-(hexyloxy)phenyl)-10,15-dihydro-5H-diindolo[3,2-a: 3',2'-c]carbazole) were synthesized and exploited in perovskite based solar cells. The energy levels of star-shaped HMDI and HPDI were tuned by symmetrically introducing electron-rich alkoxy side groups. These soluble and easily synthesized materials exhibit optical transparency in the visible region, high thermal stability and have suitable HOMO values with respect to perovskite, making them an ideal HTM candidate for efficient perovskite solar cells. The HPDI molecule-based devices gave competitive power conversion efficiencies of similar to 11% under AM 1.5G illumination. The facile synthetic approach using inexpensive precursor materials will facilitate triazatruxene-based molecules to be further exploited in thin film organic-inorganic perovskite solar cells and needs optimization to enhance power conversion efficiency

Perovskite Solar Cells Employing Molecularly Engineered Zn(II) Phthalocyanines as Hole-transporting Materials

Amino donor groups-substituted zinc(II) phthalocyanines (ZnPcs) BI25, BL07 and BL08 were obtained via cyclotetramerization of suitable phthalonitriles that were synthesized by Pd catalyzed amination reaction between 4-iodophthalonitrile and a selected secondary amine. The BI25, BL07 and BL08 ZnPcs were characterized using spectroscopic and electrochemical methods, and used as hole transporting layer in perovskite solar cells. The open circuit voltage (V-OC) of perovskite solar cell devices reached close to 1 V, and the short-circuit current density (J(SC)) values evaluated from J-V curves were 16.2, 8.42, and 16.9 mA/cm(2), respectively, demonstrating influence of the HOMO levels of ZnPcs. A power conversion efficiency of 11.75% was obtained in the case of BI25, which is the highest value ever reported using ZnPcs as HTMs in perovskite solar cells with traditional device geometry. (C) 2016 Elsevier Ltd. All rights reserved