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A series of novel polymers (P1–P6) derived from the combination of different units (including thiophene, triarylamine, and spirobifluorene) were successfully synthesized, completely characterized, and used as hole-transporting materials (HTMs) for perovskite solar cells (PSCs). Solar cells with some of these materials as HTMs showed very good performances of almost 13% (12.75% for P4 and 12.38% for P6) even without additives, and devices based on these new HTMs show relatively improved stability against temperature compared to those based on PTAA. The presence of dopant additives has been linked to long-term degradation, which is the main barrier to the large-scale commercialization of this innovative type of solar cell. Obtaining efficient PSCs without using dopants could represent a further step toward improvement of long-term stability and thus their introduction into the market.

This work reports on a new strategy to design low-temperature (≤ 200°C) sintered dye-sensitized solar cells (ltDSSCs) with enhanced charge collection efficiencies (coll), photoconversion efficiencies, and stabilities under continuous operation conditions. This is accomplished by integrating into the electrodes a new class of hybrid mesoporous Ru(II) complex-TiO2 nanoparticles (TiO2_Ru_IS), obtained by in-situ bottom-up construction of dyesensitized titania using the Ru(II) N3 dye as building blocks. The most important assets of the TiO2_Ru_IS hybrid nanoparticles are i) a remarkable dye stability due to the integration of the dye within the anatase network and ii) a small nanoparticle size to enhance charge transport/collection processes. The latter is encouraging for tackling the two main bottlenecks in lt-DSSCs, that is, moderate efficiencies and low device stabilities. Our results evidence that devices with electrodes featuring a mixture of P25 and TiO2_Ru_IS show an enhanced charge transport and reduced electron recombination processes. The incorporation of TiO2_Ru_IS into the electrode leads to an increase ofcoll from 46% for P25 reference up to 60% for P25:TiO2_Ru_IS (80:20 wt%) device. As a final optimization, TiO2_Ru_IS was also applied as a top layer in a multi-layered device architecture, leading to coll of around 74%. The latter result in lt-DSSCs featuring efficiencies of 8.75% and lifetimes of 600 h under device operation conditions.

Naphthalene‐diimide (NDI)‐based molecules have shown an interesting behaviour within the field of perovskite solar cells, thanks to their promising application as electron transporting materials. In this paper, three novel NDI‐containing molecules are synthesized and fully characterized, more specifically two polymers and an analogue small molecule. Each one of the NDI units contains an amine, either tertiary or quaternary, which is a moiety known for improving the conductivity. The newly synthesized compounds are suitable for the use as n‐type buffer layers on the top of PC61BM, thanks to their appropriate energy levels and their solubility in polar solvents. The photovoltaic performances of the NDI‐containing cells are highly comparable to those of the reference cells, which contain bathocuproine (BCP) as buffer layer. Furthermore, the stability of the NDI‐containing cells is higher than that of the BCP reference.