Theoretical Study of the Effects of Carrier Transport, Capture, and Escape Processes on Solar Cells with Embedded Nanostructures

Chin-Yi Tsai

doi:10.1155/2014/972597

Abstract

A theoretical model is proposed to study the effects of carrier transport, escape, and capture processes on solar cells with embedded nanostructures. The theoretical results clearly indicate that the carrier transport, escape, and capture times are important physical quantities affecting the performance of solar cells with embedded nanostructures and they should be fully considered in device design, such as the selection of the optimal band-gap energy of the nanostructures. The beneficial results from the embedded nanostructures cannot be warranted. Slow escape processes and long transport time will make the nanostructures act as gigantic recombination sites and cause a detrimental effect on the bulk solar cell. The results show that solar cells embedded with nanostructures of very small band-gap energy materials will suffer from extremely slow escape processes due to a very large potential difference between the nanostructures and the bulk host material; therefore, their output photocurrent could be inferior to their bulk counterparts without the nanostructures. The beneficial results from the embedded nanostructures to the solar cells can only be realized by their long carrier lifetime and fast escape time.

Highlights

There exist ongoing efforts to improve the efficiency of solar cells
Solar cells embedded with nanostructures are even inferior to their bulk counterparts, and the inclusion of nanostructures will only degrade the efficiency of the device and totally lose its purpose
A theoretical model is proposed to study the effects of carrier transport, capture, and escape processes on solar cells with embedded nanostructures

Summary

Introduction

Solar cells embedded with nanostructures of smaller band-gap energy to form various quantum structures, such as quantum wells, wires, or dots, undoubtedly provide an interesting subject worth of more investigations [1, 2]. Using different materials to absorb different spectral portions of sunlight is a well-known practice for improving the efficiency of solar-cells. It can be achieved by using various methods and configurations, such as beam-splitting, mechanically stacking, heterojunction, and tandem structures. The effects of carrier transport, capture, and escape processes on solar cells embedded with nanostructures are not well studied yet [5,6,7]

Theoretical Model

Results and Discussion

Conclusion