Role of Carbon Dots in Polymer Based Bulk Heterojunction Solar Cells to Achieve High Open Circuit Voltage
Carbon quantum dots (C-dots) as replacement for conventional fullerenes has been studied and applied to achieve cost-effective (photovoltaic) PV technology. Synthesis of hydrophobic C-dots was done via carbonization of carbohydrates, in the presence of amine. Hydrophobic C-dots along with polymer form homogeneous and clear dispersion in chloroform. It results in the casting of undisrupted film to work as perfect active layer in polymer based bulk heterojunction (BHJ) solar cells. Photoluminescence quenching was done to study photo induced charge transfer in between polymer (as donor) and C-dots (as acceptor). UV-Vis absorbance depicted better utilization of solar spectrum on adding C-dots into polymer. Contact angle of 110° on ITO, evidenced the hydrophobic nature of synthesized C-dots. Fabrication of BHJ solar cells (in direct configuration) using PFO-DBT as donor and C-dots as acceptor, along with optimization gives significant solar cell J-V characteristics. The power conversion efficiency of nearly 3% with noticeable VOC of 0.85 V has been obtained. Replacement of fullerene with more economic C-dots lead to improvement in cost to performance ratio of polymer solar cells. Additionally, the stability measurement exhibits that the highly stable C-dots maintain high VOC in the device for quite longer duration.
Dr. Rajni is thankful to Council of Scientific and Industrial Research (CSIR) for providing Senior Research Fellowship to carry out the research work for completion of her doctorate under Academy of Scientific Innovation and Research (AcSIR). Also, authors acknowledge the Nano Research Facility (NRF) at IIT Delhi for HRTEM characterization.