Highly Efficient Inorganic-Organic Heterojunction Solar Cells Based On Polymer And Cdx (X = Se, Te) Quantum Dots: An Insight From A Theoretical Study

Using the density functional method, we explore the potentiality of the recently synthesized CdX (X = Se, Te) QD/P3HT composites in solar energy conversion devices. Our study reveals that inorganic/organic hybrid CdXQD/P3HT nanocomposites with larger-size CdX QDs exhibit type-II band alignment, suggesting an efficient charge separation upon photoexcitation. But for smaller-size QDs, the composites show type-I band alignment that are devoid of charge separation and thus are not suitable for solar cell applications. To remove this obstacle, we focus on the chemical modification to polymer P3HT. The substitution of hydrogen at the beta-position of each thiophene ring of polymer by the electron-withdrawing group (CN) results in a type-II band alignment and achieves spatial charge separation even for smaller-size quantum dots (QDs). Finally, we calculated the power conversion efficiency (PCE) of CdXQD-and CN-functionalized P3HT nanocomposites. The maximum calculated PCE value of 10.82% is achieved, which makes the nanocomposites highly competitive with other reported heterojunction solar cells.