Buried MoO x /Ag Electrode Enables High-Efficiency Organic/Silicon Heterojunction Solar Cells with a High Fill Factor.

Silicon (Si)/organic heterojunction solar cells based on poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) and n-type Si have attracted wide interests because they promise cost-effective and high-efficiency. However, the limited conductivity of PEDOT:PSS leads to an inefficient hole transport efficiency for the heterojunction device. Therefore, a high dense top-contact metal grid electrode is required to assure the efficient charge collection efficiency. Unfortunately, the large metal grid coverage ratio electrode would lead to undesirable optical loss. Here, we develop a strategy to balance PEDOT:PSS conductivity and grid optical transmittance via a buried molybdenum oxide/silver grid electrode. In addition, grid electrode coverage ratio is optimized to reduce its light shading effect. The buried electrode dramatically reduces the device series resistance, which leads to a higher fill factor (FF). With the optimized buried electrode, a record FF of 80% is achieved for a flat Si/PEDOT:PSS heterojunction devices. With further enhancement adhesion between PEDOT:PSS film and Si substrate by a chemical cross-linkable silance, a power conversion efficiency (PCE) of 16.3% for organic/textured Si heterojunction devices is achieved. Our results provide a path to overcome the inferior organic semiconductor property to enhance organic-Si heterojunction solar cell.