MoO3 Nanodots Decorated CdS Nanoribbons for High-Performance, Homojunction Photovoltaic Devices on Flexible Substrates

The p-n homojunctions are essential components for high-efficiency optoelectronic devices. However, the lack of p-type doping in CdS nanostructures hampers the fabrication of efficient photovoltaic (PV) devices from homojunctions. Here we report a facile solution-processed method to achieve efficient p-type doping in CdS nanoribbons (NRs) via a surface charge transfer mechanism by using spin-coated MoO3 nanodots (NDs). The NDs-decorated CdS NRs exhibited a hole concentration as high as 8.5 x 10(19) cm(-3), with the p-type conductivity tunable in a wide range of 7 orders of magnitude. The surface charge transfer mechanism was characterized in detail by X-ray photoelectron spectroscopy, Kelvin probe force microscopy, and first-principle calculations. CdS NR-homojunction PV devices fabricated on a flexible substrate exhibited a power conversion efficiency of 5.48%, which was significantly better than most of the CdS nanostructure-based heterojunction devices, presumably due to minimal junction defects. Devices made by connecting cells in series or in parallel exhibited enhanced power output, demonstrating the promising potential of the homojunction PV devices for device integration. Given the high efficiency of the surface charge transfer doping and the solution-processing capability of the method, our work opens up unique opportunities for high-performance, low-cost optoelectronic devices based on CdS homojunctions.