Simulation-guided design of ETL-Free and HTL-Free all-polymer solar cells: Front and back work function engineering

• For the first time, designs without the electron-transporting layer (ETL) and without the hole-transporting layer (HTL) are proposed utilizing this all-polymer solar cell. • Optimizing the front contact featuring a work function of 3.6 eV in the ETL-free cell, and the back contact featuring a work function of 5.4 eV in the HTL-free cell resulted in boosting the PCE up to 20.99% and 27.23%, respectively. • This study highlights the significance of optimizing charge transport pathways in APSCs, providing a novel approach to enhance efficiency while simplifying device architecture. Recently, all-polymer solar cells (APSCs) have shown competitive output performance parameters amongst thin film solar cells. In this work, N-type PBDB:T and P-type PZT:C1 polymers are utilized as a blend, forming the absorber photoactive film for suggested charge transport layer (CTL)-free APSCs. Previous experimental results demonstrated 14.91% power conversion efficiency (PCE) using a device with stacked nanoscale thin film layers PEDOT:PSS/PBDB:T/PZT:C1/PFN-Br APSC, with ITO and Ag as the front and back contacts, respectively. For the first time, designs without the electron-transporting layer (ETL) and without the hole-transporting layer (HTL) are proposed utilizing this all-polymer solar cell. In order to engineer the band alignment across the APSC, the role of the front contact in the ETL-free cell, and the role of the rear contact in the HTL-free cell are investigated. Optimizing the front contact featuring a work function of 3.6 eV in the ETL-free cell, and the back contact featuring a work function of 5.4 eV in the HTL-free cell resulted in boosting the PCE up to 20.99% and 27.23%, respectively. To validate and simulate the proposed designs, SCAPS-1D simulations were employed, offering valuable insights into energy band alignment and charge transport mechanisms. This study highlights the significance of optimizing charge transport pathways in APSCs, providing a novel approach to enhance efficiency while simplifying device architecture.