Integrated Design of Organic Hole Transport Materials for Efficient Solid‐State Dye‐Sensitized Solar Cells

Abstract

A series of triphenylamine‐based small molecule organic hole transport materials (HTMs) with low crystallinity and high hole mobility are systematically investigated in solid‐state dye‐sensitized solar cells (ssDSCs). By using the organic dye LEG4 as a photosensitizer, devices with X3 and X35 as the HTMs exhibit desirable power conversion efficiencies (PCEs) of 5.8% and 5.5%, respectively. These values are slightly higher than the PCE of 5.4% obtained by using the state‐of‐the‐art HTM Spiro‐OMeTAD. Meanwhile, transient photovoltage decay measurement is used to gain insight into the complex influences of the HTMs on the performance of devices. The results demonstrate that smaller HTMs induce faster electron recombination in the devices and suggest that the size of a HTM plays a crucial role in device performance, which is reported for the first time.

Tailor-Making Low-Cost Spiro[fluorene-9,9′-xanthene]-Based 3D Oligomers for Perovskite Solar Cells

“…This indicates that X55 might exhibit as fast or even faster hole transport in a solid thin film formed by the compound (Table 1). 35 To investigate the charge-carrier mobility of the three HTMs, we analyzed space-charge-limited currents (SCLCs) and two-contact electrical conductivity; the fitted J-V curves for each material (detailed information can be found in the Supplemental Information), as well as the corresponding hole mobility and conductivity data, are depicted in Figures 2C and 2D and Table 1. Clearly, X55 exhibited a good hole mobility of 6.81 3 10 À4 cm 2 $V À1 $s À1 , which is much higher than that of X54 (8.25 3 10 À5 cm 2 $V À1 $s À1 ) and Spiro-OMeTAD (1.48 3 10 À4 cm 2 $V À1 $s À1 ).…”

Metal-free organic dyes for TiO2 and ZnO dye-sensitized solar cells

“…In metal-free organic dye a donor-acceptor couple, D-π-A, is present, in which the electron donor is not only able to tune the electronic coupling with the acceptor, but also determines the molecule adsorbed state on the titania or zinc oxide nanocrystal in DSSC devices. Several investigations about the donor modification were reported in recent years; in particular, the organic dye D35 18 and derivatives (Y123 19 , LEG4 20 ), featuring phenyl extended triphenyl amine donor, gained popularity because of the prominent performance in DSSC devices. It was reported that, when an extended triphenyl amine is used as the donor group, an up-shift of TiO 2 conduction band (CB) edge (CBE) can be observed on account of the increased net surface dipole moment of the adsorbed dye molecules.…”

“…However, the higher photogenerated electron transport rate contributes to cell performance for ZnO, while in TiO 2 a low recombination rate, combined with higher dye loading and faster electron injection boost η . Due to its large availability and uncountable obtainable low dimension structures, such as nanorods/nanowires 20 44 , nanotubes 45 46 , nanosheets 47 48 , nanoflowers 49 , tetrapods 50 51 52 and hierarchical aggregates 53 54 55 , ZnO is a very interesting alternative to TiO 2 to investigate. Application of these nanostructured ZnO photoanodes in DSSC significantly enhanced η , compared to simple ZnO nanoparticle mesoporous films.…”

Composite Hole‐Transport Materials Based on a Metal‐Organic Copper Complex and Spiro‐OMeTAD for Efficient Perovskite Solar Cells

“…As shown in Figure b, the highest occupied molecular orbital (HOMO) energy level of CuH and Spiro‐OMeTAD are around −5.38 and −5.22 eV, respectively, indicating that both HTMs should work well PSCs effectively extracting holes from the perovskite layer transporting them to the Au counter electrode. The lowest occupied molecular orbital (LUMO) energy levels of CuH (−2.93 eV) and Spiro‐OMeTAD (−2.06 eV) are higher than the conduction band of the perovskite material, which block electron transport from the perovskite layer to Au and hence suppress carrier recombination …”