Influence of Donor Groups of Organic D−π–A Dyes on Open-Circuit Voltage in Solid-State Dye-Sensitized Solar Cells

Abstract

In solid-state dye-sensitized solar cells (ssDSCs), the poor pore filling of the mesoporous semiconductor and the short diffusion length of charge carriers in the hole-transport material (HTM) have limited the mesoscopic titania layer to a thickness of 2–3 μm. To increase the amount of light harvested by ssDSCs, organic dyes with high molar extinction coefficients are of great importance and have been the focus of intensive research. Here we investigate ssDSCs using an organic D−π–A dye, coded Y123, and 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene as a hole-transport material, exhibiting 934 mV open-circuit potential and 6.9% efficiency at standard solar conditions (AM1.5G, 100 mW cm–2), which is a significant improvement compared to the analogue dyes C218, C220, and JK2 (V oc values of 795, 781, and 914 mV, respectively). An upward shift in the conduction band edge was observed from photovoltage transient decay and impedance spectroscopy measurements for devices sensitized with Y123 and JK2 dyes compared to the device using C220 as sensitizer, in agreement with the high photovoltage response of the corresponding ssDSCs. This work highlights the importance of the interaction between the HTM and the dye-sensitized TiO2 surface for the design of ssDSCs.

Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO2: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J–V Hysteresis

“…However, the recombination lifetimes in solid state DSSCs, which also have mpTiO 2 /SOT contact, are on the order of 1 ms, 100 times longer than the slow decay seen here. 38,39,46 Other Possible Sources of Fast TPV Decays…”

Molecular Engineering of Organic Dyes with a Hole‐Extending Donor Tail for Efficient All‐Solid‐State Dye‐Sensitized Solar Cells

“…Ourr esultsi ndicate that the newly designed HPT unit can extendh ole propagation of the dye relative to those of the alkyl or 2,4-bis(hexyloxy)benzene donor terminusest om aintain the spiro-OMeTAD + remote from the e(TiO 2 )b eyondt he minimum distance ( % 2nm) that spiro-OMeTADc an approach to the TiO 2 surface. [7,39,46] Thus, our TASr esultsj ustify the molecular design with the HPTa saholeextended tail in the D-A-p-A configuration to form ac ompact surface-blocking layer for the retardation of CR kinetics to enhance the V OC of the device. [47,48] The internal acceptorB TD in OD9 also plays an important role to decrease the rate of charge recombination between TiO 2 and spiro-OMeTAD to obtain the largest V OC in this series of metalfree organic sensitizers.…”

“…[38] The absorption band in the wavelength region 350-450nm arises from the p-p*t ransition, for which the wavelength of the absorption maximum is affected by the HBT or the HPT long chain at the terminus of the donor group. [39] For example, OD5 and OD6 exhibit similar spectral features in the CT transition (e % 310 4 Lmol À1 cm À1 at l = 515 nm), butt he maximum of the p-p*t ransition of OD6 is blue-shifted by approximately 10 nm with respect to that of OD5 (Table 1), which shows the effect of p conjugation between the HBT and the HPT terminal groups at the donor site. In contrast, OD7 shows spectralf eatures similart o those of OD6, which indicates that the two thiophene units in OD7 are not coplanar to affect the pconjugation.D ye OD8 showsasignificantly redshifted CT band.…”

Investigation of novel anthracene-bridged carbazoles as sensitizers and Co-sensitizers for dye-sensitized solar cells

“…The dye is a crucial component of DSSCs, greatly influencing the power conversion efficiency and stability of the device [4,5]. Several metal-free organic dyes, including triarylamine dyes [6][7][8][9][10][11], coumarin dyes [12][13][14][15][16], carbazole dyes [17][18][19][20][21], indoline dyes [22][23][24][25], heteroanthracene dyes [26][27][28], tetrahydroquinoline dyes [29,30], N,N-dialkylaniline dyes [31][32][33][34], merocyanine dyes [35,36], hemicyanine dyes [37,38], squarine dyes [39][40][41], perylene dyes [42,43], anthraquinone dyes [44], oligothiophene dyes [45], and boradiazaindacene (BODIPY) dyes [46][47][48], have been tested in DSSCs. These metal free organic dyes are commonly designed in the donor-π-conjugation-acceptor (D-π-A) configuration.…”