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Plasmonic nanomeshes: their ambivalent role as transparent electrodes in organic solar cells

Scientific Reports, Published online: 15 February 2017; doi:10.1038/srep42530

Publication date: 15 March 2017
Source:Journal of Power Sources, Volume 344
Author(s): Huifeng Zheng, Weiqi Wang, Yangqiao Liu, Jing Sun
Compact, pinhole-free and PbI2-free perovskite films, are desirable for high-performance perovskite solar cells (PSCs), especially if large columnar grains are obtained in which the adverse effects of grain boundaries will be minimized. However, the conventional solid-state reaction methods, originated from the two-step method, failed to grow columnar grains of CH3NH3PbI3 in a facile way. Here, we demonstrate a strategy for growing large columnar grains of CH3NH3PbI3, by less-crystallized nanoporous PbI2 (ln-PbI2) film enhanced solid-state reaction method. We demonstrated columnar grains were obtainable only when ln-PbI2 films were applied. Therefore, the replacement of compact PbI2 by ln-PbI2 in the solid-sate reaction, leads to higher power conversion efficiency, better reproducibility, better stability and less hysteresis. Furthermore, by systematically investigating the effects of annealing temperature and duration, we found that an annealing temperature ≥120 °C was also critical for growing columnar grains. With the optimal process, a champion efficiency of 16.4% was obtained and the average efficiency reached 14.2%. Finally, the mechanism of growing columnar grains was investigated, in which a V P b ″ -assisted hooping model was proposed. This work reveals the origins of grain growth in the solid-state reaction method, which will contribute to preparing high quality perovskite films with much larger columnar grains.

Graphical abstract

Publication date: 15 March 2017
Source:Journal of Power Sources, Volume 344
Author(s): Yuyuan Xue, Ying Wu, Yuan Li
With the dramatic development of the power conversion efficiency (PCE) of perovskite solar cells (PVSCs), device lifetime has become one of the extensive research interests and concerns. To enhance the device durability, developing high performance dopant-free hole transport materials (HTMs) is a promising strategy. Herein, two new C3-symmetric HTMs with phenol core, TCP-OH and TCP-OC 8 are readily prepared and show ultra-wide energy band-gap and excellent film-formation property. PCEs of 16.97% and 15.28% are achieved with pristine TCP-OH and TCP-OC 8 film as HTMs, respectively, even though their hole mobilities are as low as 10⁻⁶ cm² V⁻¹ s⁻¹. Phenol acts as hole trap in traditional concept, however, TCP-OH shows higher hole mobility than that of TCP-OC 8 . Moreover, TCP-OH shows higher glass transition temperature and better matching band alignment than those of TCP-OC 8 . Phenol shows great potential as building block for HTMs as it is beneficial to enhance hole mobility of HTMs. Moreover, our study demonstrates an interesting viewpoint to design HTMs with the balance of hole mobility and electron blocking effect.

Graphical abstract