Improving the Photovoltaic Performance of TiO2/P3HT Hybrid Solar Cell by Interfacial Modification

Abstract

In this paper, highly ordered and vertically oriented one-dimensional TiO2 nanorod arrays were prepared firstly on F-SnO2 (FTO) conductive glass by hydrothermal method, then an amphiphilic organic triphenylamine-type dye 2-(5-(4(diphenylamino)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)acetic acid (M for short) was adsorbed on its surface. After spin-coating organic polymer poly(3-hexylthiophene) (P3HT for short), we fabricated the modified hybrid solar cell device with the structure of FTO/TiO2/M/P3HT/PEDOT:PSS/Au. The transient photocurrent of the electrodes reflects the pn heterojunction is existent indeed in the hybrid electrode. The contact angle changes from 13.9° for pure TiO2 to 112.6° for M-modified sample. This hydrophobic surface facilitates TiO2 further contacting with polymer P3HT. The steady state photoluminescence (PL) emission spectra shows stronger quenching of PL intensity, and PL lifetime fitted from the PL decay curves decreased for the M-modified hybrid film. These conclusions implie the effective charge transfer between P3HT and TiO2, which could suppress the charge recombination. Electrochemical impedance analysis showed that the electron recombination resistance and electron lifetime were increased after interfacial modification. The photovoltaic performance of the modified hybrid cell along with the unmodified one was tested. The open-circuit voltage (Voc), short-circuit current (Jsc), fill factor (FF) are increased for the modified device, and resulting the power conversion efficiency (η) of 1.61%. In addition, the mechanism of the cell and the charge transfer process were investigated preliminarily. The interfacial modifier might be functioned as a “bridge” to transfer electrons to inorganic semiconductor, and transfer holes to polymer also. The modifier could possibly mediate charge transfer in one direction from P3HT to TiO2 for electron accepting and result in more efficient charge separation due to the cascaded energy levels. This work may provide a useful method for increasing the performance of hybrid solar cells by interface modification.