Independent humidity engineering of MAPbI3 absorbers and hole transport layers for enhanced performance in perovskite solar cells

This study extends beyond the analysis of performance variations in MAPbI3 fabricated under different relative humidity (RH) conditions by independently preparing the Spiro-OMeTAD hole transport layer (HTL) under decoupled humidity conditions. This approach enables a systematic investigation of the individual impact of RH on each layer. Moderate humidity levels, particularly around 60 % RH, significantly enhance device efficiency by simultaneously improving the crystallinity of the perovskite layer and the electrical conductivity of the HTL. Structural and optoelectronic characterizations indicate that residual PbI2 formed under moderate humidity conditions effectively passivates shallow trap states at the MAPbI3 interface, suppressing non-radiative recombination and facilitating more efficient charge extraction. Moreover, selectively tuning the humidity for each functional layer reveals that humidity-controlled HTL fabrication independently contributes to overall device performance, highlighting the critical role of layer-specific environmental control. In contrast to previous studies that applied uniform humidity conditions across all layers, this work distinguishes the individual effects of humidity modulation during each fabrication step. These findings offer valuable insights for developing scalable, humidity-resilient fabrication strategies aimed at achieving high-efficiency and stable PSCs.