Core Fusion Engineering of Hole-Transporting Materials for Efficient Perovskite Solar Cells

Abstract

In this work, a fused polycyclic aromatic hydrocarbon (PAH) core was introduced to construct hole-transporting materials (HTMs) for perovskite solar cells (PSCs). It was found that with the extended π-conjugation of the fused core, the hole mobility was enhanced along with the better film-forming property for (tetrakis-(hexylphenyl)-dronaphthotetraphenodithiophene)bis(N,N-bis-(methoxyphenyl)aniline) (MPA-DTP) compared to that for (tetrakis-(hexylphenyl)-indacenodithiophene)bis(N,N-bis(methoxyphenyl)aniline) (MPA−IDT). The smooth and condensed film morphology is beneficial for interfacial contact, leading to reduced nonradiative recombination. As a result, planar PSCs based on MPA−DTP displayed a superior efficiency of 19.20%, far exceeding that of the MPA−IDTbased device (15.64%) and slightly higher than those with spiro-OMeTAD (19.11%). We believe that fused core engineering is envisioned as a promising strategy for developing highly efficient HTMs in PSCs.

Deciphering the Reduced Loss in High Fill Factor Inverted Perovskite Solar Cells with Methoxy-Substituted Poly(Triarylamine) as the Hole Selective Contact

“…Perovskite solar cells (PSCs) with inverted (p-i-n) configuration attracted increasing attention due to their low-temperature fabrication, reliable repeatability, and negligible hysteresis. A certified efficiency of over 22% has been reported, which, though, is still inferior to their n-i-p structured counterparts. − To further boost the device performance, researchers endeavored to investigate the origin of the efficiency losses in a complete device under operational conditions. − They generally agreed that the recombination loss, occurring either in the bulk perovskite (PVSK) or at the heterojunction interface, is the primary culprit in hindering a higher power conversion efficiency (PCE). − Especially, recombination at the interface is found to be more severe than in bulk. As Wolfgang Pauli once famously said, “while God created the solids, the Devil created the surfaces.” Huang et al reported that the trap densities of charges at the interfaces are 1–2 orders of magnitude greater than that of the film interior and constitute the predominant pathways contributing to recombination losses in perovskite solar cells …”

Effects of Heteroatom and Extending the Conjugation on Linear Hole-Transporting Materials for Perovskite Solar Cells

“…5,9−11 However, due to its stiff price and complicated multistep synthesis, it is vital to find original HTMs and efficient candidates for spiro-OMeTAD. 12,13 Until now, a great deal of novel alternatives have been widely reported, mainly containing inorganic materials, organic molecules, and polymers. 14−20 Among the organic HTMs, small molecules have been widely studied because of their facile and well-defined molecule structure, easy molecular tailoring, and inessential batch difference.…”

“…So far, the most commonly recognized efficient HTM for PSCs is the 2,2′,7,7′-tetrakis­( N,N -di- p -methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). ,− However, due to its stiff price and complicated multistep synthesis, it is vital to find original HTMs and efficient candidates for spiro-OMeTAD. , Until now, a great deal of novel alternatives have been widely reported, mainly containing inorganic materials, organic molecules, and polymers. − Among the organic HTMs, small molecules have been widely studied because of their facile and well-defined molecule structure, easy molecular tailoring, and inessential batch difference. − Generally, molecular HTMs can be classified as spiro, linear, and star materials according to the shape. Many reports have proved the linear molecules as efficient HTMs for PSCs, ,− and their conjugated bridges exhibit great effects on the device performance. The bridge engineering of linear HTMs has been thought to be the effective method to develop neoteric and efficient HTMs for high-performance PSCs. , …”

Thermally StableD2hSymmetric Donor‐π‐Donor Porphyrins as Hole‐Transporting Materials for Perovskite Solar Cells

“…[14,15] It is, therefore, a hot topic to develop novel, low-cost, stable HTMs with equally high performance as Spiro-OMeTAD. [16][17][18][19][20][21][22][23][24][25] Macrocyclic phthalocyanines and porphyrin derivatives showed great potential as the alternative HTMs due to their high thermal/photochemical stability, easily tailored peripheral/ non-peripheral substituents, and tunable electro/photochemical properties. [26][27][28][29][30][31][32][33][34] In 2016, Yeh and co-workers demonstrated Zn II porphyrin HTM consisting of meso-5,15bis(ethynylaniline) backbones bearing bilateral butyl chains, and the resulted PSCs achieved a promising efficiency of 16.60 %, comparable to that of Spiro-OMeTAD with a PCE of 18.03 %.…”

“…However, Spiro‐OMeTAD suffered from limited hole mobility, low conductivity, lengthy synthetic process, and hazardous reagents involved in the synthesis [14, 15] . It is, therefore, a hot topic to develop novel, low‐cost, stable HTMs with equally high performance as Spiro‐OMeTAD [16–25] . Macrocyclic phthalocyanines and porphyrin derivatives showed great potential as the alternative HTMs due to their high thermal/photochemical stability, easily tailored peripheral/non‐peripheral substituents, and tunable electro/photochemical properties [26–34] .…”