High‐Efficiency Perovskite Solar Cells Using Molecularly Engineered, Thiophene‐Rich, Hole‐Transporting Materials: Influence of Alkyl Chain Length on Power Conversion Efficiency

Abstract

The synthesis and characterization of a series of novel small-molecule hole-transporting materials (HTMs) based on an anthra [1,2-b:4,3-b′:5,6-b′′:8,7-b′′′]tetrathiophene (ATT) core are reported. The new compounds follow an easy synthetic route and have no need of expensive purification steps. The novel HTMs were tested in perovskite solar cells (PSCs) and power conversion efficiencies (PCE) of up to 18.1 % under 1 sun irradiation were 2 measured. This value is comparable with the 17.8 % efficiency obtained using spiroOMeTAD as a reference compound. Similarly, a significant quenching of the Photoluminescence in the first nanosecond is observed, indicative of effective hole transfer.Additionally, the influence of introducing aliphatic alkyl chains acting as solubilizers on the device performance of the ATT molecules is investigated. Replacing the methoxy groups on the triarylamine sites by butoxy-, hexoxy-or decoxy-substituents greatly improved the solubility of the compounds without changing the energy levels, yet at the same time significantly decreasing the conductivity as well as the PCE, 17.3 % for ATT-OBu, 15.7 % for ATT-OHex and 9.7 % for ATT-ODec.

Over 20% PCE perovskite solar cells with superior stability achieved by novel and low-cost hole-transporting materials

“…The LUMO levels of HTMs are calculated to be -2.44 eV,-2.77 eV and -2.12 eV, which are more positive than that of mixperovskite (-3.9 eV). 24 These results agreed well with the trend derived from DFT calculations.…”

Facile Synthesis of Polycyclic Aromatic Hydrocarbon (PAH)–Based Acceptors with Fine‐Tuned Optoelectronic Properties: Toward Efficient Additive‐Free Nonfullerene Organic Solar Cells

“…[12d,17] However, it is difficult to control the ratio of additives accurately and the device performance reproducibility could be affected adversely. [27] Nevertheless, PAHs have been largely overlooked for developing emerging FREAs, and there have been very few reports in the burgeoning field of nonfullerene solar cells based on PAH building blocks (e.g., naphthalene, fluorene, and dithienopicenocarbazole) (Figure 2), [28] lacking systematic investigations on the structure-property-performance correlations of PAHbased FREAs. [19] Therefore, it is imperative to develop new FREAs with facile chemical synthesis and good compatibility with additive-free fabrication protocol when blended with donor materials.…”

Facilely Synthesized spiro[fluorene‐9,9′‐phenanthren‐10′‐one] in Donor–Acceptor–Donor Hole‐Transporting Materials for Perovskite Solar Cells

“…Recently,o rganic-inorganic halide perovskite solar cells (PSCs) have attracted considerable attention because of their outstanding performance in converting sunlight to electricity at al ow cost compared with silicon-based photovoltaict echnology.T he first PSCs, as ana-lyzed by Miyasaka in 2009, had power conversion efficiency (PCE) of 3.8 %. [12][13][14] To overcome these issues, numerouss tudies have focusedo nl ow-costp roduction without as piro-based linkage in the HTM, mainly using acene, [15] carbazole, [16][17][18][19][20][21][22][23] indole, [24][25][26] phenothiazine, [27] phenoxazine, [28] thiophene, [29][30][31][32][33][34][35] triarylamine, [36][37][38][39] triazateuxene, [40][41][42][43] and truxene. [11] In the conventional devicec onfiguration, 2,2',7,7'-tetrakis[N,N-di(4methoxyphenyl)amino]-9,9'-spirobifluorene( Spiro-OMeTAD) is generally used as the hole-transporting material( HTM) and has demonstrated PCEs of 20-21 %i nP SCs.…”