Boosting Perovskite Solar Cells Performance and Stability through Doping a Poly‐3(hexylthiophene) Hole Transporting Material with Organic Functionalized Carbon Nanostructures

Abstract

Perovskite solar cells (PSCs) are demonstrating great potential to compete with second generation photovoltaics. Nevertheless, the key issue hindering PSCs full exploitation relies on their stability. Among the strategies devised to overcome this problem, the use of carbon nanostructures (CNSs) as hole transporting materials (HTMs) has given impressive results in terms of solar cells stability to moisture, air oxygen, and heat. Here, the use of a HTM based on a poly(3‐hexylthiophene) (P3HT) matrix doped with organic functionalized single walled carbon nanotubes (SWCNTs) and reduced graphene oxide in PSCs is proposed to achieve higher power conversion efficiencies (η = 11% and 7.3%, respectively) and prolonged shelf‐life stabilities (480 h) in comparison with a benchmark PSC fabricated with a bare P3HT HTM (η = 4.3% at 480 h). Further endurance test, i.e., up to 3240 h, has shown the failure of all the PSCs based on undoped P3HT, while, on the contrary, a η of ≈8.7% is still detected from devices containing 2 wt% SWCNT‐doped P3HT as HTM. The increase in photovoltaic performances and stabilities of the P3HT‐CNS‐based solar cell, with respect to the standard P3HT‐based one, is attributed to the improved interfacial contacts between the doped HTM and the adjacent layers.

Interfacial Morphology Addresses Performance of Perovskite Solar Cells Based on Composite Hole Transporting Materials of Functionalized Reduced Graphene Oxide and P3HT

“…An effect of the content of the nanofillers dispersed in the P3HT blend on the final device performance was evidenced by testing HTMs with different loadings of RGO‐PhOMe. The HTM with the highest nanofiller content (4 wt.%) was significantly outperforming the others, suggesting a correlation between CNS wt.% and PSC efficiency, likely through the improvement of the hole extraction process at the perovskite/HTM interface . This was indeed achieved thanks to the homogeneity of dispersion of the RGO‐PhOMe species in P3HT, which allowed to build optimized selective contacts.…”

“…In this regard, resorting to chemical functionalization of pristine CNSs can be useful when the process is sufficiently controllable to avoid an excessive disruption of the native electronic structure . In the past, we have applied a coupled covalent chemical functionalization/sedimentation‐based separation (SBS) strategy to obtain homogeneous dispersion of RGO in a P3HT matrix . The chemical functionalities selected for binding to the RGO flakes surface were the 4‐(methoxy)phenyl groups (thus leading to species named as RGO‐PhOMe), introduced through a Tour‐type direct arylation reaction and previously demonstrated to be able to improve dispersibility of other CNSs in organic solvents and polymers .…”

“…The chemical functionalities selected for binding to the RGO flakes surface were the 4‐(methoxy)phenyl groups (thus leading to species named as RGO‐PhOMe), introduced through a Tour‐type direct arylation reaction and previously demonstrated to be able to improve dispersibility of other CNSs in organic solvents and polymers . RGO‐PhOMe@P3HT blends, enriched in the most soluble fractions of the functionalized RGO derivative thanks to the SBS process, were then employed as hole transporting materials (HTMs) in standard architecture perovskite solar cells, providing increased efficiency and stability to the devices in comparison to the use of a bare P3HT HTM . An effect of the content of the nanofillers dispersed in the P3HT blend on the final device performance was evidenced by testing HTMs with different loadings of RGO‐PhOMe.…”

“…The resulting derivatives have been blended with P3HT applying the previously used SBS protocol, providing different amounts of functionalized RGO homogeneously dispersed in the polymer solution, depending on the substituents grafted on the CNS surface. From each family of RGO derivatives, i.e., the thienyl‐based and the alkyl‐based ones, the blend with the highest wt.% of functionalized RGOs has been selected to be tested as HTMs in PSCs.…”

Nanocarbons as Electron Donors and Acceptors in Photoinduced Electron-Transfer Reactions

“…[113][114][115][116][117] The introduction of SWCNTs into a carbon CE for mesoscopic structured PKSCs enhanced the hole collection efficiency due to its' 1D excellent conduction with a high hole mobility. 118 Transient absorbance measurements indicate that holes are rapidly and efficiently transferred from the MAPbI 3 valence band to the adjacent SWCNT layer, providing mechanistic information regarding the role of SWCNT layers as efficient hole extraction layers in PKSCs. 119 Incorporation of multi-walled carbon nanotubes (MWCNTs) in the bulk of the active layer of PKSCs has been shown to reduce charge recombination and increase the open circuit voltage.…”