Teaching an Old Anchoring Group New Tricks: Enabling Low-Cost, Eco-Friendly Hole-Transporting Materials for Efficient and Stable Perovskite Solar Cells

Abstract

As a key component in perovskite solar cells (PVSCs), hole-transporting materials (HTMs) have been extensively explored and studied. Aiming to meet the requirements for future commercialization of PVSCs, HTMs which can enable excellent device performance with low cost and eco-friendly processability are urgently needed but rarely reported. In this work, a traditional anchoring group (2-cyanoacrylic acid) widely used in molecules for dye-sensitized solar cells is incorporated into donor–acceptor-type HTMs to afford MPA-BT-CA, which enables effective regulation of the frontier molecular orbital energy levels, interfacial modification of an ITO electrode, efficient defect passivation toward the perovskite layer, and more importantly alcohol solubility. Consequently, inverted PVSCs with this low-cost HTM exhibit excellent device performance with a remarkable power conversion efficiency (PCE) of 21.24% and good long-term stability in ambient conditions. More encouragingly, when processing MPA-BT-CA films with the green solvent ethanol, the corresponding PVSCs also deliver a substantial PCE as high as 20.52% with negligible hysteresis. Such molecular design of anchoring group-based materials represents great progress for developing efficient HTMs which combine the advantages of low cost, eco-friendly processability, and high performance. We believe that such design strategy will pave a new path for the exploration of highly efficient HTMs applicable to commercialization of PVSCs.

A Coplanar π‐Extended Quinoxaline Based Hole‐Transporting Material Enabling over 21 % Efficiency for Dopant‐Free Perovskite Solar Cells

“…The 1 H NMR spectra of TQ3 and TQ4 with or without PbI 2 were recorded using [D 6 ]DMSO as solvent. As shown in the Supporting Information, Figure S18, the presence of PbI 2 leads to a slight shift to high‐field for the H atom on quinoxaline core, suggesting a weak intermolecular interactions between quinoxaline core and Pb 2+ [31] . The XPS results further supported such interaction.…”

“…As shown in the Supporting Information, Figure S18, the presence of PbI 2 leads to a slight shift to high-field for the H atom on quinoxaline core, suggesting a weak intermolecular interactions between quinoxaline core and Pb 2+ . [31] The XPS results further supported such interaction. Compared to the pristine perovskite film, the Pb 4f peaks are shifted to higher binding energies after coating a thin TQ4 film on the perovskite (Supporting Information, Figure S19).…”

Intramolecular Electric Field Construction in Metal Phthalocyanine as Dopant‐Free Hole Transporting Material for Stable Perovskite Solar Cells with >21 % Efficiency

“…Thus, the highly hygroscopic Li‐bis(trifluoromethane sulfonyl) imide (Li‐TFSI) and tert‐butylpyridine (tBP) were adopted into these HTMs, [18, 19] which not only increase the production costs of PSCs, but also accelerate the degradation of perovskite layer [20–22] . Thus, seeking for the new dopant‐free and low‐cost HTMs is of vital importance for the fabrication of efficient PSCs [23–28] …”

Efficient Inverted Perovskite Solar Cells with Low Voltage Loss Achieved by a Pyridine‐Based Dopant‐Free Polymer Semiconductor

“…In addition to introducing an additional passivation layer, directly endowing the HTLs with passivation functions should be a more efficient way to reduce the NRR in PVSCs, [30–32] since it can further simplify the device fabrication and avoid hindering charge transfer at the interface. Moreover, since the HTL is deposited before the perovskite layer in inverted devices, the HTL with passivation functions is expected to increase the interface contact and further to improve the crystal quality of perovskite films, leading to the decrease of NRR within the perovskite bulk.…”