Optimized Doping of Diffusion Blocking Layers and Their Impact on the Performance of Perovskite Photovoltaics

The roll-to-roll printing production process for hybrid organic-inorganic perovskite solar cells (PSCs) demands thick and high-performance solution-based diffusion blocking layers. Inverted (p-i-n) PSCs usually incorporate solution-processed PC₇₀BM as the electron-transporting layer (ETL), which offers good electron charge extraction and passivation of the perovskite active layer grain boundaries. Thick fullerene diffusion blocking layers could benefit the long-term lifetime performance of inverted PSCs. However, the low conductivity of PC₇₀BM significantly limits the thickness of the PC₇₀BM buffer layer for optimized PSC performance. In this work, we show that by applying just enough N-DMBI doping principle, we can maintain the power conversion efficiency (PCE) of inverted PSCs with a thick (200 nm) PC₇₀BM diffusion blocking layer. To better understand the origin of an optimal doping level, we combined the experimental results with simulations adapted to the PSCs reported here. Importantly, just enough 0.3% wt N-DMBI-doped 200 nm PC₇₀BM diffusion blocking layer-based inverted PCSs retain a high thermal stability at 60 °C of up to 1000 h without sacrificing their PCE photovoltaic parameters.