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

Abstract

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 azomethine–EDOT central scaffold, resulting in a more pronounced redshift. The three new derivatives have been tested in combination with the state‐of‐the‐art triple‐cation perovskite [(FAPbI3)0.87(MAPbBr3)0.13]0.92[CsPbI3]0.08 in standard mesoporous PSCs. Remarkable power conversion efficiencies of 17.48 % and 18.30 % were measured for DTTX‐1 and DTTX‐2, respectively, close to that measured for the benchmarking HTM spiro‐OMeTAD (18.92 %), under 100 mA cm−2 AM 1.5G solar illumination. PSCs with DTTX‐3 reached a PCE value of 12.68 %, which is attributed to the poorer film formation in comparison to DTTX‐1 and DTTX‐2. These PCE values are in perfect agreement with the conductivity and hole mobility values determined for the new compounds and spiro‐OMeTAD. Steady‐state photoluminescence further confirmed the potential of DTTX‐1 and DTTX‐2 for hole‐transport applications as an alternative to spiro‐OMeTAD.

Selenophene‐Based Hole‐Transporting Materials for Perovskite Solar Cells

“…TPASe‐2 ‐based devices reached a lower efficiency than those using TPASe‐1 , due to the significant decrease of the V oc (903 mV) that leads to a smaller FF (0.61) with an enhanced hysteresis. The low homogeneity and uniformity of the selenium‐containing HTM films favors the interfacial charge recombination, which contributes to the low FF values obtained for the novel HTMs [45] . The devices incorporating spiro‐OMeTAD as HTM surpassed the PCE values provided by the selenophene derivatives, reaching a maximum PCE of 17.78 % correlated with the enhanced values of V oc (1056 mV), J sc (23.28 mA cm −2 ), and FF (0.73).…”

“…The low homogeneity and uniformity of the selenium-containing HTM films favors the interfacial charge recombination, which contributes to the low FF values obtained for the novel HTMs. [45] The devices incorporating spiro-OMeTAD as HTM surpassed the PCE values provided by the selenophene derivatives, reaching a maximum PCE of 17.78 % correlated with the enhanced values of V oc (1056 mV), J sc (23.28 mA cm À 2 ), and FF (0.73). Figure 5b displays the external quantum efficiencies (EQEs) of the new selenium-containing HTMs and the reference of spiro-OMeTAD and the integrated photocurrents deduced for TPASe-1 (22.42 mA cm À 2 ), TPASe-2 (22.43 mA cm À 2 ), and spiro-OMeTAD (23.34 mA cm À 2 ) are in good agreement with those obtained from the J-V measurements.…”

From truxenes to heterotruxenes: playing with heteroatoms and the symmetry of molecules

“…255,256 The semi-conductivity of 5,10,15-triazatruxenes can be modulated by increasing their degree of aggregation via peripheral functionalization 228,235,[257][258][259] or the presence of donor subunits (Scheme 29). [260][261][262][263][264] Devices based on functionalized systems can achieve a photocurrent generation efficiency of up to 18.8%. 265 The use of 5,10,15-triazatruxenes in OPVs is not only limited to their semiconductive properties.…”

Synthesis of Hexaazatruxenes by Consecutive N−H/C−H Coupling Using a Hypervalent Iodine Reagent and Evaluation of Their Photophysical Properties

“…The obtained trithio‐ and trioxatruxenes exhibited relatively good quantum yields in the solid state, which was explained by aggregation‐induced emission (AIE) effects. Among the reported heterotruxenes, azatruxenes have been proven to provide high hole mobility, enhancing hole transport and being widely used in hole‐transporting materials (HTMs) of perovskite solar cells (PSCs) and efficient deep‐blue emission OLED [9–14] . Although heteroatom‐containing truxenes are expected to be building blocks with good photophysical properties, to the best of our knowledge, no examples of truxenes containing more than three heteroatoms have been reported.…”