Correlating Interface Heterostructure, Charge Recombination, and Device Efficiency of Poly(3-hexyl thiophene)/TiO2 Nanorod Solar Cell

• Published in: Langmuir Vol. 27; no. 24; pp. 15255 - 15260
• Main Authors: Zeng, Tsung-Wei, Ho, Chun-Chih, Tu, Yu-Chieh, Tu, Guan-Yao, Wang, Lee-Yih, Su, Wei-Fang
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 20.12.2011
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Materials: Nano-and Mesostructured Materials, Polymers, Gels, Liquid Crystals, Composites; Surface physical chemistry; Atomic force microscopy; Modification; Binary compound; Five membered ring; Surface charge; Recombination; Dyes; Film; Device; Transition element compounds; Boiling point; Thiophene; Conversion; Resistance; Sulfur heterocycle; Lifetime; Efficiency; Morphology; Phase separation; Force microscopy; Impedance; Titanium oxide; Molecular mass; Interface
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la203533u

The charge recombination rate in poly(3-hexyl thiophene)/TiO2 nanorod solar cells is demonstrated to correlate to the morphology of the bulk heterojunction (BHJ) and the interfacial properties between poly(3-hexyl thiophene) (P3HT) and TiO2. The recombination resistance is obtained in P3HT/TiO2 nanorod devices by impedance spectroscopy. Surface morphology and phase separation of the bulk heterojunction are characterized by atomic force microscopy (AFM). The surface charge of bulk heterojunction is investigated by Kelvin probe force microscopy (KPFM). Lower charge recombination rate and lifetime have been observed for the charge carriers in appropriate heterostructures of hybrid P3HT/TiO2 nanorod processed via high boiling point solvent and made of high molecular weight P3HT. Additionally, through surface modification on TiO2 nan,orod, decreased recombination rate and longer charge carrier lifetime are obtained owing to creation of a barrier between the donor phases (P3HT) and the acceptor phases (TiO2). The effect of the film morphology of hybrid and interfacial properties on charge carrier recombination finally leads to different outcome of photovoltaic I–V characteristics. The BHJ fabricated from dye-modified TiO2 blended with P3HT exhibits 2.6 times increase in power conversion efficiency due to the decrease of recombination rate by almost 2 orders of magnitude as compared with the BHJ made with unmodified TiO2. In addition, the interface heterostructure, charge lifetime, and device efficiency of P3HT/TiO2 nanorod solar cells are correlated.