Tetrasubstituted Thieno[3,2- b]thiophenes as Hole-Transporting Materials for Perovskite Solar Cells

Three hole-transporting materials (HTMs) were prepared following a straightforward synthetic route by cross-linking arylamine-based ligands with a simple thieno[3,2-b]thiophene (TbT) core. The novel HTMs were fully characterized with standard techniques to gain insight into their optical and electrochemical properties and were incorporated in solution-processed mesoporous (FAPbI3)0.85(MAPbBr3)0.15 perovskite-based solar cells. The similar molecular structure of the synthesized HTMs was leveraged to investigate the role that the bridging units between the conjugated TbT core and the peripheral arylamine units plays on their properties and thereby on the photovoltaic response. A remarkable po…

Isomerism effect on the photovoltaic properties of benzotrithiophene-based hole-transporting materials

Engineering of inorganic–organic lead halide perovskites for photovoltaic applications has experienced significant advances in recent years. However, the use of the relatively expensive spiro-OMeTAD as a hole-transporting material (HTM) poses a challenge due to dopant-induced degradation. Herein we introduce two new three-armed and four-armed HTMs (BTT-4 and BTT-5) based on isomeric forms of benzotrithiophene (BTT). The isomerism impact on the optical, electrochemical and photophysical properties and the photovoltaic performance is systematically investigated. Perovskite solar cells (PSCs) using BTT-4 and BTT-5 as HTMs show remarkable light-to-energy conversion efficiencies of 19.0% and 18.…

Non-Planar and Flexible Hole-Transporting Materials from Bis-Xanthene and Bis-Thioxanthene Units for Perovskite Solar Cells

Two new hole-transporting materials (HTMs), BX-OMeTAD and BTX-OMeTAD, based on xanthene and thioxanthene units, respectively, and bearing p-methoxydiphenylamine peripheral groups, are presented for their use in perovskite solar cells (PSCs). The novelty of the newly designed molecules relies on the use of a single carbon-carbon bond ‘C−C’ as a linker between the two functionalized heterocycles, which increases the flexibility of the molecule compared with the more rigid structure of the widely used HTM spiro-OMeTAD. The new HTMs display a limited absorbance in the visible region, due to the lack of conjugation between the two molecular halves, and the chemical design used has a remarkably i…

Heteroatom Effect on Star-Shaped Hole-Transporting Materials for Perovskite Solar Cells

Improving the Long‐Term Stability of Doped Spiro‐Type Hole‐Transporting Materials in Planar Perovskite Solar Cells

The improvement of the long-term stability of perovskite-based solar cells (PSCs) toward commercialization is closely linked to the development of cutting-edge charge-transporting materials. The progress on the design and the synthesis of new hole-transporting materials (HTMs) is synergistically attaining both top efficiencies and promising stability. Herein, the synthesis and characterization of two doped-HTMs based on electron-rich spiranic cores, namely, 9H-quinolinophenoxazine (spiro-POZ) and 9H-quinolinophenothiazine (spiro-PTZ), are presented. The novel HTMs exhibit excellent solubility, optimal highest occupied molecular orbital energy, and excellent thermal stability with glass tran…

Hole-Transporting Materials for Perovskite Solar Cells Employing an Anthradithiophene Core

A decade after the report of the first efficient perovskite-based solar cell, development of novel hole-transporting materials (HTMs) is still one of the main topics in this research field. Two of the main advance vectors of this topic lie in obtaining materials with enhanced hole-extracting capability and in easing their synthetic cost. The use of anthra[1,9-bc:5,10-b'c']dithiophene (ADT) as a flat π-conjugated frame for bearing arylamine electroactive moieties allows obtaining two novel highly efficient HTMs from very cheap precursors. The solar cells fabricated making use of the mixed composition (FAPbI3)0.85(MAPbBr3)0.15 perovskite and the novel ADT-based HTMs show power conversion effi…

Perovskite Solar Cells: Heteroatom Effect on Star-Shaped Hole-Transporting Materials for Perovskite Solar Cells (Adv. Funct. Mater. 31/2018)

Saddle-like, π-conjugated, cyclooctatetrathiophene-based, hole-transporting material for perovskite solar cells

A flexible, saddle-like, π-conjugated skeleton composed of four fused thiophene rings forming a cyclooctatetrathiophene (CoTh) with four triphenylamines (CoTh-TTPA) is presented as a hole-transporting material (HTM) for perovskite solar cells. The new HTM shows a bright red color stemming from a direct conjugation between the TPA groups and the central CoTh scaffold. This results in a charge transfer band due to the combination of the weak acceptor moiety, the CoTh unit, and the electron-donating p-methoxytriphenylamine groups. CoTh-TTPA exhibits a suitable highest-occupied molecular orbital (HOMO) level in relation to the valence band edge of the perovskite, which ensures efficient hole ex…

Azatruxene‐Based, Dumbbell‐Shaped, Donor–π‐Bridge–Donor Hole‐Transporting Materials for Perovskite Solar Cells

Three novel donor-π-bridge-donor (D-π-D) hole-transporting materials (HTMs) featuring triazatruxene electron-donating units bridged by different 3,4-ethylenedioxythiophene (EDOT) π-conjugated linkers have been synthesized, characterized, and implemented in mesoporous perovskite solar cells (PSCs). The optoelectronic properties of the new dumbbell-shaped derivatives (DTTXs) are highly influenced by the chemical structure of the EDOT-based linker. Red-shifted absorption and emission and a stronger donor ability were observed in passing from DTTX-1 to DTTX-2 due to the extended π-conjugation. DTTX-3 featured an intramolecular charge transfer between the external triazatruxene units and the azo…

CCDC 1813461: Experimental Crystal Structure Determination

Related Article: Inés García-Benito, Iwan Zimmermann, Javier Urieta-Mora, Juan Aragó, Joaquín Calbo, Josefina Perles, Alvaro Serrano, Agustín Molina-Ontoria, Enrique Ortí, Nazario Martín, Mohammad Khaja Nazeeruddin|2018|Adv.Energy Mater.|28|1801734|doi:10.1002/adfm.201801734

CCDC 1813460: Experimental Crystal Structure Determination

Related Article: Inés García-Benito, Iwan Zimmermann, Javier Urieta-Mora, Juan Aragó, Joaquín Calbo, Josefina Perles, Alvaro Serrano, Agustín Molina-Ontoria, Enrique Ortí, Nazario Martín, Mohammad Khaja Nazeeruddin|2018|Adv.Energy Mater.|28|1801734|doi:10.1002/adfm.201801734

CCDC 1813459: Experimental Crystal Structure Determination

Related Article: Inés García-Benito, Iwan Zimmermann, Javier Urieta-Mora, Juan Aragó, Joaquín Calbo, Josefina Perles, Alvaro Serrano, Agustín Molina-Ontoria, Enrique Ortí, Nazario Martín, Mohammad Khaja Nazeeruddin|2018|Adv.Energy Mater.|28|1801734|doi:10.1002/adfm.201801734