Strategies of modifying spiro-OMeTAD materials for perovskite solar cells: a review

Abstract

The effects of different doping strategies and corresponding doping mechanisms on the performance and stability of PSCs were reviewed.

The impact of fluorine atoms on a triphenylamine-based dopant-free hole-selective layer for perovskite solar cells

“…One of the most studied HTL is Spiro-OMeTAD in which the poor electrical properties and high cost limit its widespread application. 13,14 Moreover, in the case of Spiro-OMeTAD, it shows absorbance near to 400 nm and competes with the perovskite light absorbance, which can decrease the PCE since in p-i-n based PSCs light passes from the HTL layer first. 15 Arguably, doping can increase the charge extraction to get collected at the contact surface of the HTL and perovskite which triggers high fill factors (FF) and open-circuit voltage (Voc).…”

The Non‐Innocent Role of Hole‐Transporting Materials in Perovskite Solar Cells

“…As discussed previously, the need to use LiTFSI as the dopant to trigger the oxidation of Spiro-based HTM formulations [24] has been shown to be a key issue for device stability, due the hygroscopic quality of the finally obtained layer, causing an undesirable water uptake from the atmosphere that ultimately reaches the perovskite photon absorber, causing its degradation toward the high-bandgap metal halide precursors. [25] While much attention has been addressed to the role of this ionic additive in influencing PSC stability, less was known until few years ago about the possible influence of the second major additive in the Spiro-HTM formulation, namely, the small organic molecule tBP. This additive is generally assumed to provide considerable help in reaching the optimal HTM morphology on top of the perovskite layer, permitting good pinhole passivation.…”

Face-on oriented hydrophobic conjugated polymers as dopant-free hole-transport materials for efficient and stable perovskite solar cells with a fill factor approaching 85%

“…1–9 Molecular 2,2′,7,7′-tetrakis-( N , N -di- p -methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD) catalyzed the initial dramatic development of PSCs in 2012, 2 and nearly surpassed all the newly developed HTMs in realizing all the record efficiencies marked on the NREL chart. 10,11 The recently certified efficiency of 25.2% was also from a device with the n–i–p configuration that employed spiro-OMeTAD as the HTM. 8,9 However, the good performance of spiro-OMeTAD heavily depends on the addition of additives like lithium bis(trifluoromethyl sulfonyl)imide (Li-TFSI) and 4- tert -butylpyridine ( t BP) to overcome the intrinsic low hole mobility and conductivity due to the symmetric globular structure and the resultant weak π–π interactions.…”