Metal halide perovskites with the general formula ABX3 (where A: cations, B: Pb, Sn, etc., and X: halides) continue to motivate the researchers in both academia and industry, owing to their excellent photophysical and optoelectronic properties, such as strong and broad absorption, ambipolar charge-carrier mobility, long carrier diffusion length, and solution processability. Organic-inorganic hybrid perovskite solar cells (PSCs) have been widely explored for their potential to be commercialized, which resulted their power conversion efficiencies (PCEs) escalated from ~3% to certified ~22% since year 2009. However, on the way to commercialization, these devices are far from realization due to the several disadvantages such as high synthesis cost, low conductivity, intrinsic acidity, and chemical instability of the standard hole transport materials (HTMs); spiro-OMeTAD (2,2,7,7-tetrakis (N, N -di-p-methoxyphenylamine)-9,9-spirobifluorene) and PEDOT:PSS (poly(3,4-ethylenedioxythiophene):styrenesulfonate). In order for PSCs to reach their full potential, significant advances need to be made in order to overcome the fundamental limitations noted above. Hence, we set out to explore the syntheses of alternative compounds as possible stable and efficient HTMs. In this study, we have designed and synthesized novel organic small molecules SA12, SA13, and SA14 consisting thieno-imidazole core with same donor and different acceptor moities to investigate their electron-withdrawing effects , and characterized for their applications as dopant-free HTMs in inverted PSCs. Characterization of these synthesized compounds involves various measurements including UV-vis absorbance, cyclic voltammetry, thermostability, thermogravimetric analysis, and differential scanning calorimetry. As indicated by the preliminary results, these HTMs are superior than the standard PEDOT:PSS with higher PCEs ~13%. A further optimization of device fabrication conditions is presently under progress and final results will be presented during the conference.

New organic hole transporting materials with various acceptors for efficient inverted (p-i-n) perovskite solar cells

2019 Spring National Meeting

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