Improved photoinduced charge carriers separation in organic-inorganic hybrid photovoltaic devices

Abstract

We demonstrate enhanced performance of a hybrid photovoltaic device, where poly[3-hexylthiophene] (P3HT) is used as active material and a solution-processed thin flat film of ZnO modified by a self-assembled monolayer (SAM) of phenyl-C61-butyric acid (PCBA) is used as electron extracting electrode. Ultraviolet photoemission spectroscopy measurements reveal an increase in the substrate work function from 3.6 to 4.1 eV upon PCBA SAM deposition due to an interfacial dipole pointing away from the ZnO. External quantum efficiency (EQE) of the SAM modified devices reached 9%, greatly improved over the 3% EQE of the unmodified devices. This corresponds to full charge separation of all photoexcitations generated in the P3HT within an exciton diffusion range from the interface.

Nanostructured Organic and Hybrid Solar Cells

“…Due to a similar HOMO and LUMO structure, both effi cient energy and charge transfer should be possible between the P3HT and the polymer dye. Another very promising sensitizer for P3HT-metal oxide devices was presented by Vaynzof et al [ 120 ] By covering fl at ZnO fi lms with a carboxylated PCBM they were able to improve the V OC , I SC and FF compared to non-modifi ed ZnO. Since the combination of P3HT and PCBM is well known to facilitate effi cient charge separation, PCBM-based sensitizers might allow high performance HSCs in the future, especially for carboxylated [6,6]-phenyl C 70 -butyric acid methyl ester (PC 70 BM), which shows a broader absorption in the visible spectrum than PCBM.…”

Amphiphilic fullerene derivative as effective interfacial layer for inverted polymer solar cells

“…However, the drawback of the fullerene-based CBL is the relatively low inherent conductivity. Therefore most of fullerene-based interfacial materials are applied as self-assembled molecular layer (SAM) to modify the zinc oxide (ZnO) but used alone, such as phosphonic acid-anchored C60 [30], carboxylic acid-anchored C60 [25], phenyl-C61-butyric acid$(PCBA) [31] and so on. Although ZnO is a potential CBL with relatively high electron mobility, the compatibility between organic polymer and inorganic metal oxide should not be ignored.…”

Simultaneous enhancement of photocurrent and open circuit voltage in a ZnO based organic solar cell by mixed self-assembled monolayers

“…SAM formation is a process where a single layer or a multilayer of molecules can be organized on a substrate by chemisorption to tailor the surface properties [19]. For example, incorporation of a SAM as the interface of two different materials was reported with enhanced electronic coupling and control over the energy gap at the polymer/inorganic junction, which reduces the interfacial recombination of excitons [20,21]. In addition, SAM between the organic/inorganic layer improves the crystallinity of the polymer thereby improving the hole mobility and overall power conversion efficiency [22].…”