Enhancing Thermal Stability and Lifetime of Solid-State Dye-Sensitized Solar Cells via Molecular Engineering of the Hole-Transporting Material Spiro-OMeTAD

Abstract

Thermal stability of hybrid solar cells containing spiro-OMeTAD as hole-transporting layer is investigated. It is demonstrated that fully symmetrical spiro-OMeTAD is prone to crystallization, and growth of large crystalline domains in the hole-transporting layer is one of the causes of solar cell degradation at elevated temperatures, as crystallization of the material inside the pores or on the interface affects the contact between the absorber and the hole transport. Suppression of the crystal growth in the hole-transporting layer is demonstrated to be a viable tactic to achieve a significant increase in the solar cell resistance to thermal stress and improve the overall lifetime of the device. Findings described in this publication could be applicable to hybrid solar cell research as a number of well-performing architectures rely heavily upon doped spiro-OMeTAD as hole-transporting material.

A Novel Dopant‐Free Triphenylamine Based Molecular “Butterfly” Hole‐Transport Material for Highly Efficient and Stable Perovskite Solar Cells

“…We note that the glass transition temperature of Z1011 is 24 °C higher than spiroOMeTAD, which retards the formation of crystalline domains within the hole-transporter layer during device aging. [38,39] Moreover, preliminary test ( Figure S7, Supporting Information) shows that the Z1011-based device is more resistant to heat stress than the device based on spiro-OMeTAD at 80 °C.…”

Stability Issues on Perovskite Solar Cells

“…Malinauskas et al argued that the fully symmetrical spiro-MeOTAD tends to be easily crystallized, which can affect the contact between the perovskite and the HTM [35]. Local asymmetry was introduced into the spiro-MeOTAD to suppress the crystal growth.…”

Copper oxide as inorganic hole transport material for lead halide perovskite based solar cells

“…However, it is known that spiro-OMETAD causes degradation in the devices performance and the field is still research active (Nogueira et al, 2004;Pudzich et al, 2006). There is some published work dedicated to the HTM layer and its effect on the stability of perovskite solar cells (PSC) (Malinauska et al, 2015;Badia et al, 2014;Nguyen et al, 2014). There is also a reasonable literature on the degradation of the performance of Dye Sensitized cell (DSC) due to the use of spiro-OMETAD O'Brien et al, 1998).…”

“…It is reasonable to expect that the same conclusions apply to PSC as the reported issues are highly associated with the spiro-OMETAD itself. These issues are mainly related to the thermal stress effects (Malinauska et al, 2015;Bailie et al, 2014;O'Brien et al, 1998) and oxidization effects (Badia et al, 2014;Nguyen et al, 2014). Additionally, Snaith et al reported recently TiO 2 -free device that showed stability of the photocurrent over 1000 h of exposure to simulated sunlight .…”