Doping Strategy for Efficient and Stable Triple Cation Hybrid Perovskite Solar Cells and Module Based on Poly(3-hexylthiophene) Hole Transport Layer

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 ((FA_1-x-y MA_x Cs_y )Pb(I_1-x Br_x )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.