Air-stable inverted structure of hybrid solar cells using a cesium-doped ZnO electron transport layer prepared by a sol-gel process

Seungchul Kwon, Kyung Geun Lim, Myungsun Shim, Hong Chul Moon, Jicheol Park, Gumhye Jeon, Jihyun Shin, Kilwon Cho, Tae Woo Lee, Jin Kon Kim

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

We have developed an air-stable inverted structure of poly(3- hexylthiophene) (P3HT):cadmium selenide (CdSe) hybrid solar cells using a cesium-doped ZnO (ZnO:Cs) electron transport layer. The ZnO:Cs layer was simply prepared at low temperature by the sol-gel process using a ZnO solution containing cesium carbonate (Cs2CO3). With increasing Cs-doping concentration, the conduction band edge of ZnO is decreased, as confirmed by scanning Kelvin probe microscopy. The energy level of ZnO:Cs is effective for electron transport from CdSe. Consequently, the power conversion efficiency (PCE) of the inverted P3HT:CdSe hybrid solar cells using the ZnO:Cs electron transport layer is 1.14%, which is significantly improved over that (0.43%) of another device without Cs. X-ray photoelectron spectroscopy analysis revealed that the amount of CdSe on the substrate (or the bottom surface) is larger compared with the air (or top) surface regardless of the P3HT:CdSe weight ratio. The vertically inhomogeneous distribution of CdSe in the hybrid solar cells gives better charge transport from CdSe to ZnO:Cs in the inverted structure of the device compared with that in the normal structure. As a result, the inverted hybrid solar cell consisting of 1:4 (wt/wt) P3HT:CdSe shows the best efficiency, while the best efficiency of a normal hybrid solar cell is achieved at 1:9 (wt/wt) P3HT:CdSe.

Original languageEnglish (US)
Pages (from-to)11802-11808
Number of pages7
JournalJournal of Materials Chemistry A
Volume1
Issue number38
DOIs
StatePublished - Oct 14 2013

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