Hybrid Solar Cells Comprising Inorganic and Organic Materials Through Vapor Phase Infiltration

The development of inorganic, organic and perovskite solar cells (SCs), has witnessed considerable progress over the past decade. Perovskite SCs, while highly efficient, encounter stability and toxicity concerns. Inorganic SCs outperform their organic counterparts in efficiency and durability but lack mechanical flexibility, motivating exploration of alternative technologies. In contrast, organic SCs offer the desired flexibility, but face the mentioned lower efficiency challenges. Despite the inherent limitations of each SC type, they have their own merits, promising a grand step forward if synergy is achieved. Combining the adaptability of organic SCs with the efficiency of inorganic ones may yield a hybrid versatile alternative. Herein, we are introducing new hybrid solar cell materials by applying vapor phase infiltration (VPI) to polymers.
We present a completely new hybrid materials set obtained after growing Sb₂S₃ and Sb₂Se₃ by VPI inside the bulk and atop of diverse polymers including Poly(3-hexylthiophene-2,5-diyl) (P3HT), poly(triaryl amine) (PTAA), Poly[N,N’-bis(4-butylphenyl)-N,N’-bisphenylbenzidine] (PolyTPD) and Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). PTAA, PolyTPD and PEDOT:PSS are excellent hole-transporting semiconducting materials, while P3HT is an efficient light absorber in the visible range. Metal chalcogenide light absorbent materials, such as Sb₂S₃ and Sb₂Se₃, have huge potential in photovoltaics owing to the suitable bandgap of 1.7 and 1.3 eV, and high light absorption coefficient above 10⁴ and 10⁵ cm⁻¹, respectively. For the VPI growth of Sb₂S₃ and Sb₂Se₃, SbCl₃/H₂S and SbCl₃/(Me₃Si)₂Se precursors were used, respectively. The hybridization process was monitored in-situ with a Quartz Crystal Microbalance (QCM). The monitoring allowed studying the saturation behavior of the VPI process and quantitatively controlling the loading of the inorganic precursors into the polymer. Scanning electron microscopy (SEM) showed infiltration in form of Sb₂S₃ and Sb₂Se₃ crystal growth throughout the whole polymer depth. TEM was used to examine the structure of the crystalline phase of the Sb₂S₃ and Sb₂Se₃ grown in the bulk and on top of the polymer.
With the fabricated polymer-inorganic hybrid materials as base, planar p-i-n SCs devices with following structures were fabricated: ITO glass/polymer-Sb₂S₃//Sb₂Se₃ /ETL/Ag and ITO glass/polymer-Sb₂S₃//Sb₂Se₃/perovskite/ETL/Ag. C60/BCP was used as an electron transport layer (ETL). With those devices, a complete photovoltaic characterization of the new set of hybrid materials was done in 16 ITO pins SCs, including the current density–voltage (J–V) characteristic under illumination, power conversion efficiencies (PCEs) and the external quantum efficiency (EQE). The results are very encouraging and offer new solutions for the design of future flexible and highly efficient SCs.