Perovskite solar cell with a fluoroalkyl phosphate ionic liquid additive drives a conducting polymer based electrochromic device

Abstract

A durable and cost-effective perovskite (PSK) solar cell was assembled, featuring a configuration of FTO/c-TiO₂/m-TiO₂-CsFAPbI₃ ​+ ​fluoroalkyl phosphate (FAP)-ionic liquid (IL)/p-type carbon. This marks the first utilization of the FAP-IL chemical additive, specifically 1-hexyl-2,3-dimethyl-imidazolium tris(pentafluoroethyl) trifluorophosphate, in the preparation of the PSK layer. This novel addition not only enhances the hydrophobic characteristics of the PSK layer, safeguarding it against moisture-induced deterioration and preserving its α-phase, but also ensures defect passivation via hydrogen bonds formed between N and F atoms in the IL with the organic cation of the PSK, thus preventing the migration of organic cations to grain boundaries. Furthermore, the lone pairs on neutral nitrogens are easily donated to under-coordinated Pb²⁺ cations, resulting in the stabilization of the PSK crystal structure. This configuration is further augmented by the attributes of carbon paste such as a high electrical conductivity (∼0.75 ​S ​cm⁻¹) and substantial hole density exceeding 10¹⁶/cm³, resulting in impressive performance metrics, with a power conversion efficiency (PCE) of ∼7.5% and prolonged stability in air. The electrical current and photovoltage generated by the PSK ​+ ​FAP-IL solar cell under illumination switch a low cost, easily processable and robust electrochromic device (ECD) based on poly (indole-6-carboxylic acid) (PICA) and poly (3,4-propylenedioxythiophene (PProDOT) layers from a yellow-green hue to a deep blue state. While the standalone PProDOT//PICA ECD delivers a transmission modulation (ΔT) of 48.8% over visible region, a coloration efficiency of 356 ​cm² ​C⁻¹ and sustains 2300+ cycles with no loss in optical contrast, but when harnessed to a PSK ​+ ​FAP-IL solar cell and exposed to 1 sun irradiance achieves a ΔT of 36.6% and a photo-coloration efficiency (η) of 14.9 ​cm² ​min⁻¹ W⁻¹, without the application of any external bias or current. This cost-effective integrated system, comprising a PSK ​+ ​FAP-IL solar cell and an ECD, not only effectively harvests solar energy but also serves as an intelligent window.