A Comparative Study on the Photovoltaic Properties of ZnX (X=S, Se, Te) QD/CNT Inorganic/Organic Hybrid Nanocomposites

摘要： 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 photovoltaic cell. Using 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 highest occupied molecular orbital of ZnXQD and conduction band minimum of CNT is very small (0.09-0.26 eV), implying huge possibilities of electron-hole recombination at ZnX:CNT interface. To overcome such 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 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.