Introduction of P3HT-based gradient heterojunction layer to improve optoelectronic performance of low-cost carbon-based perovskite solar cell

Abstract Perovskite solar cells (PSC) have achieved great success in the last decade in photovoltaic applications. The power conversion efficiency (PCE) has rapidly improved from 3.8% in 2009 to 25.6% in 2021. Despite this growth spurt in efficiency, PSCs are still plagued with problems related to long term operational stability which limits its commercial scalability. One of the main problems associated with PSC is the formation of charge defects and interfacial traps arising due to uncoordinated lead ions in the perovskite interface. The stability of perovskite layer is crucial for better charge extraction of PSC. In the present study, we have devised a method to passivate the perovskite layer with a P3HT based gradient heterojunction layer (GHL) introduced between perovskite and hole transport layer under ambient conditions. This type of GHL when introduced into perovskite interface would passivate the uncoordinated Pb2+ ions, reduce the non-radioactive recombination losses and improve the hydrophobicity of perovskite solar cell for better resistance against heat and moisture stressors. The PSCs with P3HT-based GHL based had a higher PCE as compared to pristine PSC, longer recombination lifetime and lesser pinholes and charge defects. Additionally, PSCs with P3HT-based GHL performed well under accelerated ageing conditions of high humidity and sudden rise and fall in temperature.