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Comparative Study on the Photovoltaic Properties of ZnX (X=S,Se,Te) QD/CNT Inorganic/Organic Hybrid Nanocomposites
Designing the efficient inorganic/organic hybrid light harvesting systems through understanding of charge generation, separation, and recombination dynamics is an important pathway for improvement of power conversion efficiency (PCE) of the photovoltaic cell. Using the density functional method, we explored the photovoltaic performance of recently synthesized ZnX (X = S, Se, Te) QD/carbon nanotube (CNT) nanocomposites. Interestingly, ZnX QD/CNT nanocomposites exhibit type-II band alignment, where hole and electron charge carriers are localized on ZnX QD and CNT, respectively. However, the energy difference between the highest occupied molecular orbital of ZnX QD and the conduction band minimum of CNT is very small (0.09–0.26 eV), implying huge possibilities of electron–hole recombination at the ZnX:CNT interface. To overcome such an unpleasant situation, we focus on chemical modification of CNT. The CNT is hydrogenated by attachment of atomic hydrogen and, next, the hydrogenated CNT is functionalized by the electron withdrawing group (−CN) in part. We found that ZnX QD and CN-functionalized hydrogenated CNT nanocomposites exhibit intended type-II band alignment and achieve high PCEs in the range of 6.73–8.38%, making them exceptionally competitive with other previously reported hybrid solar cells.