Since the advent of organic–inorganic hybrid methylammonium (MA) lead halide MAPbX3 perovskites as active materials for photovoltaic applications in 2009, the PCE of perovskite-based solar cells (PSCs) has dramatically increased from the initial 3.8% to a recently certified 22.1%. Emerging from this groundbreaking discovery, an unprecedented scientific research has sprouted in the field of photovoltaics due to their exceptional physical properties. Therefore, the development of cost-effective HTMs with high efficiency along with a good stability is an important task to address. Polycyclic aromatic hydrocarbons bearing arylamine moieties have demonstrated to be a successful approach for designing new highly efficient HTMs for PSCs. Conventionally, the π-extended conjugation associated with the planar and electron-rich structure of the fused heterocycles enable them to show strong stacking through intermolecular interactions (π-π, S-S), thereby bestowing enhanced hole-carrier mobilities. This behaviour is beatifully exemplified by anthra[1,2-b:4,3-b′:5,6-b′′:8,7-b′′′]tetrathiophene-based (ATT) HTMs previously reported. On the other hand, three-dimensional (3D) HTMs show excellent solubility in organic solvents, which is beneficial for the formation of the hole transport layer on top of the perovskite layer, leading to remarkable device performance. Here we report a readily available new class of multi-armed hole transporting materials based on 3D extended pi-conjugation of the central cores. Devices were fabricated using state-of-the-art mixed anion mixed halide perovskite composition with the nominal formula [FAPbI3]0.85[MAPbBr3]0.15 (FA = formamidinium, MA = methylammonium). The performance of the solar cells employing the novel HTMs were measured under simulated 1 sun irradiation and conversion efficiencies beyond 18 % were measured.

Tailoring hole-transporting materials for perovskites solar cells

255th National Meeting (2018)

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