Diphenylamine‐Substituted Carbazole‐Based Hole Transporting Materials for Perovskite Solar Cells: Influence of Isomeric Derivatives

Abstract

A series of new branched hole transporting materials (HTMs) containing two diphenylamine‐substituted carbazole fragments linked by a nonconjugated methylenebenzene unit is synthesized and tested in perovskite solar cells. Synthesis of the investigated materials is performed by a simple two‐step synthetic procedure providing a target product in high yield. The isolated materials demonstrate good thermal stability and majority of the investigated compounds exist in an amorphous state, which is advantageous as there is no risk of crystallization directly in the film. The highest charge drift mobility of µ0 = 4 × 10−4 cm2 V−1 s−1, measured at weak electric fields, is by ca. one order of magnitude higher than that of Spiro‐OMeTAD under identical conditions. From the perovskite solar cell testing results, it can be seen that performance of two new HTMs (V885 and V911) is on a par with Spiro‐OMeTAD. Due to the ease of synthesis, good thermal, optical and photophysical properties, this type of molecules hold great promise for practical application in commercial perovskite solar cells.

Self‐Assembled Hole Transporting Monolayer for Highly Efficient Perovskite Solar Cells

“…For a PTAA film, spin‐coated from a 2 mg mL −1 toluene solution on ITO, an I p value of 5.18 eV was obtained, which is, within the measurement uncertainty of ≈0.03 eV, the same as a previously reported value of 5.16 eV . Bulk V1036 showed an I p of 5.04 eV, which is a typical value for this chromophore . For the 100% V1036 SAM formed on ITO, I p = 4.98 eV was obtained, which is in good agreement with the bulk material value.…”

Carbazole-Terminated Isomeric Hole-Transporting Materials for Perovskite Solar Cells

“…However, based on the statistical data, V1221 shows the highest reproducibility among the series. Interestingly, the “half” molecule V1207 showed a comparable PCE of 16.44%, which is several times higher than the observed trend between the twin and “half” systems in our previous report . One possible explanation could be that the extension of the π-conjugated system with two extra carbazole units improves the charge transport in the film and facilitates the hole extraction.…”

Molecularly Engineered Low-Cost Organic Hole-Transporting Materials for Perovskite Solar Cells: The Substituent Effect on Non-fused Three-Dimensional Systems

“…Both 3 and 4 show similar T g at 107 °C, while 1 and 2 display at 137 °C that is near to spiro-OMeTAD (125 °C) . The lower T g of 3 and 4 might be attributed to more disordered molecular packing because of the meta substitution and less intermolecular interaction that consecutively leads to a lower compact film formation . Thus, no difference was found in terms of thermal properties between the alkylthio-substituted fluorene and dialkoxy-fluorene moiety.…”