Cost management and toxic waste generation are two key issues that must be addressed before the commercialization of perovskite optoelectronic devices. We report a groundbreaking strategy for eco-friendly and cost-effective fabrication of highly efficient perovskite solar cells. This strategy involves the usage of a high volatility co-solvent, which dilutes perovskite precursors to a lower concentration (<0.5 M) while retaining similar film quality and device performance as a high concentration (>1.4 M) solution. More than 70% of toxic waste and material cost can be reduced. Mechanistic insights reveal ultra-rapid evaporation of the co-solvent together with beneficial alteration of the precursor colloidal chemistry upon dilution with co-solvent, which in-situ studies and theoretical simulations confirm. The co-solvent tuned precursor colloidal properties also contribute to the enhancement of the stability of precursor solution, which extends its processing window thus minimizing the waste. This strategy is universally successful across different perovskite compositions, and scales from small devices to large-scale modules using industrial spin-coating, potentially easing the lab-to-fab translation of perovskite technologies.

As the hole transport layer (HTL) for perovskite solar cells (PSCs), poly(3‐hexylthiophene) (P3HT) has been attracting great interest due to its low‐cost, thermal stability, oxygen impermeability, and strong hydrophobicity. In this work, a new doping strategy is developed for P3HT as the HTL in triple‐cation/double‐halide ((FA1−x−yMAxCsy)Pb(I1−xBrx)3) mesoscopic PSCs. Photovoltaic performance and stability of solar cells show remarkable enhancement using a composition of three dopants Li‐TFSI, TBP, and Co(III)‐TFSI reaching power conversion efficiencies of 19.25% on 0.1 cm2 active area, 16.29% on 1 cm2 active area, and 13.3% on a 43 cm2 active area module without using any additional absorber layer or any interlayer at the PSK/P3HT interface. The results illustrate the positive effect of a cobalt dopant on the band structure of perovskite/P3HT interfaces leading to improved hole extraction and a decrease of trap‐assisted recombination. Non‐encapsulated large area devices show promising air stability through keeping more than 80% of initial efficiency after 1500 h in atmospheric conditions (relative humidity ≈ 60%, r.t.), whereas encapsulated devices show more than >500 h at 85 °C thermal stability (>80%) and 100 h stability against continuous light soaking (>90%). The boosted efficiency and the improved stability make P3HT a good candidate for low‐cost large‐scale PSCs.

In the present work we used some crystallization trends which could be classified as a Crystal Engineering (CE) approach, for deposition of a pure cubic-phase thin film of CH3NH3PbI3 (MAPbI3) on the surface of a mesoporous TiO2 layer.

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