Scientists from Syracuse University, South Dakota State University and Huzhou University have examined the use of polyaniline as a material for improved perovskite solar cells. The team demonstrated a facile, low-cost fabrication route for polyaniline hole transport mechanisms that display enhanced power conversion efficiency compared to conventional PEDOT:PSS hole transport layers in perovskites. This could provide a route toward low-cost, high-efficiency perovskite solar cells.
PEDOT:PSS is a commonly used material in perovskites, used as a hole transport layer between the photoactive perovskite layer and indium tin oxide layer. Using PEDOT:PSS improves the power conversion efficiency of perovskite solar cells. However, several issues have been observed with PEDOT:PSS. One of the fundamental issues is the degradation of active layers and defect formation associated with the large particle size of this material. Moreover, the use of this material as a hole transport layer is hindered by issues with low electrical conductivity limits and cost.
Due to these issues, research has recently focused on using alternative materials as hole transport layers. Several inorganic materials have shown promise for this purpose, such as CuI, CuSCN, NiOx, MoS2, and CuOx. Another strategy that has been demonstrated to produce favorable power conversion efficiencies is using CPE-K in inverted perovskite solar cells.
Other materials explored as promising candidates include transparent conducting polymers, which display enhanced conductivity and stability. Amongst these polymeric materials, polyaniline (PANI) has shown particular promise. Polyaniline has several beneficial attributes such as low cost, environmental stability, high performance, facile synthesis methods, thin film transparency, superior processibility, and high purity. These make it an ideal candidate for use in perovskite solar cell hole transport layers.
Several studies have investigated the benefits of polyaniline, which can be easily synthesized from aniline by chemical, photochemical, electrochemical, and enzyme-catalyzed routes. Doping polyaniline with various chemicals has produced devices with promising power conversion efficiencies. Researchers have developed large-area polyaniline films for the production of optoelectronic modules.
The new paper has proposed a method for preparing polyaniline films for use in perovskites. The authors have prepared a p-type doped polyaniline-based hole transport layer using cyclic voltammetry.
High electrical conductivity was demonstrated in the synthesized polyaniline electrode using nitric acid doping. Experimental analysis and comparative photovoltaic studies demonstrated an enhanced power conversion efficiency of 16.94% in inverted perovskite solar cells, higher than previously reported with polyaniline-based hole transport mechanisms.
Preparing the inverted polyaniline-based perovskite solar cell via electrochemical methods produced a device with lower Voc and FF and higher Jsc compared to conventional PEDOT:PSS devices. The authors have attributed this to the lower work function of polyaniline compared to PEDOT:PSS. Voc is decreased, but hole extraction is enhanced. Work function was increased using LiTFSI doping of the electrolyte solution.