Overcoming the thickness paradox: Systematical optimization of inverted polymer solar cells

• Thickness of functional layers are key factors for solar cell device performance.
• The paradox in inverted device are overcome by rationally controlling layer thickness.
• A synergistic effect on promoting the overall photovoltaic behaviors are obtained.
• The interaction between device performance and layer thickness are in-depth explored.

Inverted structure comes out to be a promising alternative for making polymer solar cells (PSC) with high efficiency and long-term stability. Vertically stacked functional layers with planar shapes often suffer contradictions in holding high optical absorption and excellent charge transfer/hindrance capability to construct well performed inverted PSC devices. Here, we give an example of rational control of the thickness of electron transport layer (ETL), hole transport layer (HTL) and organic active layer (OAL) to achieve a synergistic effect on promoting the overall photovoltaic behaviors. With in-depth exploration of the interaction between device performance and layer thickness, we obtain the optimized device ITO/ZnO Ncs (45 nm)/P3HT:PCBM (70 nm)/MoO3 (1 nm)/Ag (70 nm) exhibiting an Voc of 0.63 V, Jsc of 12.52 mA/cm2, FF of 54% and PCE of 4.26%.