Efficient bulk heterojunction hybrid solar cells with graphene-silver nanoparticles composite synthesized by microwave-assisted reduction

Herein, we present a simple, eco-friendly one-step microwave-assisted reduction (MWAR) that can produce silver nanoparticles (Ag NPs) and reduced graphene oxide (rGO) in the form of Ag-rGO composites for application in heterojunction hybrid solar cells. The field-effect transistor fabricated with the MWAR Ag-rGO composite showed p-type behavior with a high mobility of 3.3×10⁵ cm² V⁻¹ s⁻¹ and conductivity of 9×10⁶ S/m which is one-order of magnitude greater than pristine graphene (i.e., 1.59×10⁵ S/m). As-synthesized Ag-rGO composite was introduced into the active layer of bulk heterojunction solar cell based on P3HT:PCBM. Compared to the P3HT:PCBM only device (i.e., control device), the Ag-rGO implemented device showed a power conversion efficiency (PCE) of 4.23%, which is about 42% increase over the control device (i.e. PCE=2.98%). This dramatic increase in PCE was found to be mainly due to an increase in short-circuit current (J_sc) from 9.55 to 12.76 mA/cm² (about 33% increase), suggesting that the incorporation of p-type Ag-rGO into the active layer enhances the charge carrier generation and fast extraction of holes to the electrode. Furthermore, the Ag-rGO composite based solar cells without encapsulation showed remarkable air stability with retaining ~90% of its original PCE and ~93% of J_sc for 30 days under ambient environment, attributed to gas barrier feature of the randomly distributed graphene sheets.