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A new class of fluorinated cyclopenta[2,1-b:3,4-b′]dithiophene (CPDT)-based small molecules, namely YC-oF, YC-mF, and YC-H, are demonstrated as hole-transporting materials (HTMs) for high-performance perovskite solar cells (PSCs). PSCs employing YC-oF as the HTM delivered an excellent efficiency of 22.41% with encouraging long-term stability. [ABSTRACT FROM AUTHOR]

Organic small molecular materials with coplanar π-conjugated system as HTMs in perovskite solar cells (PSCs) have attracted considerable attention due to their high charge transport capability and thermal stability. Herein, three novel pentafulvalene-fused derivatives with or without fluorine atoms incorporated (YSH-oF and YSH-mF and YSH-H, respectively) are designed, synthesized, and applied as hole-transporting materials (HTMs) in PSCs fabrication. The fluorinated HTMs, YSH-oF and YSH-mF, exhibited higher hole mobility and better charge extraction at the perovskite/HTM interface than non-fluorinated one do, presumably due to the closer intermolecular π-π packing interactions. As a result, small-area (0.09 cm2) PSCs made with YSH-oF and YSH-mF achieved an impressive power conversion efficiency (PCE) of 23.59% and 22.76% respectively, with negligible hysteresis, in contrast with the 20.57% for the YSH-H-based devices. Furthermore, for large-area (1.00 cm2) devices, the PSCs employing YSH-oF exhibited a PCE of 21.92%. Moreover, excellent long-term device stability is demonstrated for PSCs with F-substituted HTMs (YSH-oF and YSH-mF), presumably due to the higher hydrophobicity. This study shows the great potential of fluorinated pentafulvalene-fused materials as low-cost HTM for efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

In this work, we have successfully synthesized 15 new examples (LLA01‐06; LinLi01‐10) of small‐molecule hole‐transporting materials (HTM) using the less explored indolocarbazole (ICbz) as core moiety. Different from previously reported ICbz HTMs, LinLi01‐10 exhibit new molecular designs in which 3,4‐ethylenedioxythiophene (EDOT) units are inserted as crucial π‐spacers and fluorine atoms are introdcued into end‐group molecules. These substantially improve the materials solubility and device power conversion efficiencies (PCEs) while fabricated in perovskite solar cells (PSC). More importantly, LinLi01‐10 are generated by a sustainable synthetic approach involving the use of straightforward C−H/C−Br couplings as key transformations, thus avoiding additional synthetic transformations including halogenation and borylation reactions called substrate prefunctionalizations usually required in Suzuki reactions. Most HTM molecules can be purified simply by reprecipitations instead of conducting column chromatography. In contrast to LLA01‐06 without additional EDOT moieties, PSC devices using LinLi01‐10 as hole‐transport layers display promising PCEs of up to 17.5 %. Interestingly, PSC devices employing seven of the LinLi01‐10 as hole‐transport molecules, respectively, are all able to show an immediate >10 % PCE (t=0) without any device oxidation/aging process that is necessary for the commercial spiro‐OMeTAD based PSCs. [ABSTRACT FROM AUTHOR]

This study improved quality of CH3NH3PbI3 (MAPbI3) perovskite films by delaying thermal annealing in the spin coating process and introducing KI and I2 to prepare MAPbI3 films that were low in defects for high-efficiency perovskite solar cells. The influences of delayed thermal annealing time after coating the MAPbI3 perovskite layer on the crystallized perovskite, the morphology control of MAPbI3 films, and the photoelectric conversion efficiency of solar cells were investigated. The optimal delayed thermal annealing time was found to be 60 min at room temperature. The effect of KI/I2 additives on the growth of MAPbI3 films and the corresponding optimal delayed thermal annealing time were further investigated. The addition of KI/I2 can improve perovskite crystallinity, and the conductivity and carrier mobility of MAPbI3 films. Under optimized conditions, the photoelectric conversion efficiency of MAPbI3 perovskite solar cells can reach 19.36% under standard AM1.5G solar illumination of 100 mW/cm2. [ABSTRACT FROM AUTHOR]