Performance Improvement in Polymer/ZnO Nanoarray Hybrid Solar Cells by Formation of ZnO/CdS-Core/Shell Heterostructures

Abstract

In this paper, performance in hybrid solar cells based on ZnO nanorod array (ZnO-NA) is significantly improved by formation of a heterostructured ZnO/CdScore/shell nanorod array (ZnO-CdS-NA), the CdS shell effects on device performance including charge transport and recombination dynamics are discussed, and a model concerning ineffective polymer phase is proposed for understanding the charge generation upon CdS shell formation. The ZnO-CdS-NAs with varied CdS shell thickness (L) were prepared by depositing CdS quantum dots on the ZnO nanorods in the ZnO-NA. Solar cells were prepared by filling the interspaces between the nanorods in ZnO-NA or ZnO-CdS-NAs with poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV). Compared to MEH-PPV/ZnO-NA devices, both open-circuit voltage (V oc ) and short-circuit current (J sc ) in MEH-PPV/ZnO-CdS-NA solar cells were dramatically improved depending on L,resulting in a peak efficiency of ca. 1.23% under AM 1.5 illumination (100 mW/cm 2 ) with a 7-fold increment for L = 6 nm. In particular, the experimental L-dependence of J sc agreed with the expectation from the proposed model and the V oc was improved from ca. 0.4 V for ZnO-NA up to around 0.8 V. Results demonstrate that in the MEH-PPV/ZnO-CdS-NA devices, the J sc correlates mainly with the charge generation subjected to the exciton generation altered by CdS shell formation, in which the polymer absorption is dominantly contributive; however, the V oc is determined by the energy difference between the highest occupied molecular orbital level of MEH-PPV and the conduction band edge of ZnO but significantly correlates with the quasi-Fermi levels of the electrons in ZnO nanorods.

Solution-processed solar cells based on inorganic bulk heterojunctions with evident hole contribution to photocurrent generation

“…80 mV is observed for increasing T c from 350 to 400 1C ( Table 1). [67][68][69][70] However, the PL data (Fig. 66 The electrons trapped by these defect states will have lower quasi-Fermi levels than in the conduction band.…”

Recent Progress in Piezo‐Phototronic Effect Enhanced Solar Cells

“…The polymer/inorganic semiconductor configuration is also a potential PV technology with versatile and flexible applicability . Yang et al studied the strain‐modulated solar cell manufactured with poly(3‐hexylthiophene) (p‐P3HT) and n‐ZnO NW .…”

Two-dimensional CdS intercalated ZnO nanorods: a concise study on interfacial band structure modification

“…11 Additionally, the successive intercalation of CdS nanoparticle on ZnO nanorod was further proved by the emerged peak of element Cd and S ( Fig. 2D and E).…”

“…9 There are some works reporting that incorporation of CdS into metal oxide framework could lead to the ultraviolet photoconductivity enhancement. 10,11 However, the concise study on band structure modification in interlayer CdS/ZnO nanorod arrays is yet discussed in most of the research findings.…”