Highly Stable Perovskite Solar Cells Fabricated Under Humid Ambient Conditions

Organometallic perovskite solar cells have gained immense attention due to their rapid increase in efficiency and compatibility with low-cost fabrication methods. However, the material's instability in humid ambient conditions has remained a key challenge for the large-scale fabrication and application of such cells. In this paper, we present devices fabricated under 50% humidity with significantly improved long-term stability through three parallel approaches. First, the small molecule hole transport material, 2,2',7,7'-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-MeOTAD) is replaced by a polymeric material Poly(3-hexylthiophene) (P3HT). Second, the device stability is further enhanced by increasing the thickness of the mesoporous titania scaffold. Finally, tetraethyl orthosilicate (TEOS) is used as a processing additive in the perovskite precursor solution to form an in situ protective layer. On our optimized device, a remarkable long-term device stability of more than 1200 h is achieved. X-ray diffraction patterns suggest more than 2500 h of material stability.