Source materials grain size effect on electrode microstructure and its effect on conventional bulk hetero-junction photovoltaics

- Effect of cathode microstructure on the device performance was studied.
- Schottky diode showed enhancement in current density.
- Enhanced JSC and PCE were observed for SolarCell-S.
- Grain size matching at metal/semiconductor interface is important better charge transfer.

In this work, the effect of silver cathode on the polymer diode and organic photovoltaic device (OPV) performance was investigated. The electron collecting contacts in diode and OPV device have been deposited from both silver pellet and nanoparticles form. Diode was fabricated by sandwiching poly(3-hexylthiophane-2,5-diyl) between ITO and Ag electrodes. It is observed that diode fabricated using Ag nanoparticles showed significant current density improvement. The enhancement in diode performance was studied by C-V measurements. Further, OPV cells fabricated using Ag nanoparticles showed improvement in current density which results in improved power conversion efficiency (PCE). The observed performance enhancements in diode and OPV device have been correlated with electrode microstructure and its interface properties. The performance enhancement in diode and OPV cells is evaluated by various electrical parameters such carrier concentration (N), density of trap states, trap distribution width (ω) and current density. These data indicate that the electrode grain size matching with the semiconductor morphology across metal/semiconductor interface is more critical for better charge transfer. Matching the roughness of the interface across the junction by use of appropriate starting material particle/grain size can help in extracting the maximum performance of an organic device.