Fabrication of Mesoporous Titania Nanoparticles with Controlled Porosity and Connectivity for Studying the Photovoltaic Properties in Perovskite Solar Cells

Abstract

Mesoporous titania (TiO2) nanoparticles (NPs) were synthesized by treating prehydrolyzed titanium precursors with polyethylene glycol (PEG). By varying the amount of PEG, their different physical properties were tuned appropriately in terms of surface area, pore size/volume, and electrical conductivity. By increasing the amount of PEG in TiO2, the surface area and pore volume of mesoporous TiO2 increased, and no direct correlation with the photovoltaic performance of perovskite solar cells was observed. In comparison, the pore size of mesoporous TiO2 first increased greatly before quickly decreasing, and a similar trend was also observed for electrical conductivity. These implied that the interparticle interaction became much stronger with an optimum amount of PEG added to form mesoporous TiO2 NPs. With an optimum molar ratio of PEG/Ti precursor at 0.75, greatly improved conductivity of mesoporous TiO2 NPs with interconnection as compared to that prepared in the absence of PEG, which was used as an electron transport layer, improved the power conversion efficiency of perovskite solar cells by ≈36%. Their greatly reduced photoluminescence after incorporating the perovskite also revealed a difference in the electron‐injection properties from the perovskite into mesoporous TiO2. This strategy highlights a versatile tool to tune mesoporous structures to achieve a cooperative effect for studying photovoltaic properties in perovskite solar cells.

On the Morphology of Nanostructured TiO2 for Energy Applications: The Shape of the Ubiquitous Nanomaterial

“…It was indeed demonstrated that the porosity of the titania scaffold, which mainly depends on the dimensions of spherical nanoparticles, determines both the perovskite coverage and crystallinity [ 98 , 99 , 100 , 101 , 102 , 103 ]. Improved coverage of the titania scaffold, obtained by increasing the porosity, gives rise to better light harvesting capabilities and hence results in higher short circuit current density generation [ 101 , 102 , 104 ]. Another consequence of the improvement of the TiO 2 scaffold coverage is the reduction of undesired electron–hole recombination, which occurs at the interface between electron and hole-transport layers; accordingly, a more effective capability of charge extraction from the perovskite was demonstrated by measuring the photoluminescence intensity, which decreases for increased titania film porosity while maintaining the same thickness.…”

“…Another consequence of the improvement of the TiO 2 scaffold coverage is the reduction of undesired electron–hole recombination, which occurs at the interface between electron and hole-transport layers; accordingly, a more effective capability of charge extraction from the perovskite was demonstrated by measuring the photoluminescence intensity, which decreases for increased titania film porosity while maintaining the same thickness. It was also reported that when maintaining the same morphology, when the titania film thickness exceeds an optimal value, the transport characteristics of the electrode [ 104 ] degrade because the perovskite coverage decreases, allowing recombination processes, and also, as widely discussed above, the number of interparticles connections decreases, lengthening the electron path. Moreover, many papers report on the impact of the perovskite grain size on the charge recombination processes not explicitly addressing the role of the titania scaffold morphology [ 100 , 105 , 106 ] but showing the improved performance of cells with larger grains, which are less affected by trap-assisted recombination at the grain boundaries.…”

Advances in Cellulose-Based Composites for Energy Applications

“…Renewable resources are produced in abundance on Earth, and include hydropower [ 71 , 72 ], wind power [ 73 ], and solar power [ 74 , 75 ]. However, harvesting these energies often requires large and complex infrastructures, which make it challenging to harness renewable energy sources in miniaturized and portable electronics.…”

Perovskite Solar Cells with Carbon‐Based Electrodes – Quantification of Losses and Strategies to Overcome Them

“…Up to now, only few reports have focused on optimizing the pore size of mesoscopic layers to improve the photovoltaic performance of the PSCs [73,74] and this strategy needs to be further explored. Naturally, methods to passivate the GBs and reduce trap densities there also represent a promising approach to reduce the V OC gap with the radiative limit.…”