Harnessing nano-particles on thin film CIGS solar cells studied by ultrabroadband pump-probe spectroscopy

• Main Authors: Li, Jia-Xing, 李嘉興
• Other Authors: 吳光雄
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/6gu8vh

碩士 === 國立交通大學 === 電子物理系所 === 104 === In this study, we have employed the ultrabroadband pump-probe spectroscopy to investigate the enhancement of efficiency in CIGS thin film solar cells via nanoparticles. Using the plasmonic effect of gold nano-partilce is an approach to improve the efficiency of CIGS solar cells. Another way is utilizing the down-shifting effect of CdSe quantum dots to enhance the photocurrent. We have performed the ultrabroadband femtosecond pump-probe spectroscopy of CuIn1-xGaxSe2 (CIGS) thin films with and without Au nanoparticles (NPs) incorporation， and elaborately analyzed the lifetimes and zero momentum for the hot carrier relaxation. The signals of enhanced photobleach (PB) and waned photoinduced absorption (PIA) attributed to surface plasmon resonance (SPR) of Au NPs were observed in the transient differential absorption spectrum. This result has suggested the carriers can be considerably excited from ground state to lower energy level. The improvements of electrical transport by suppressing the surface recombination of photoinduced carriers via enhanced local electromagnetic field (LEMF) was also confirmed by extracted hot carrier lifetime and calculated electromagnetic field distribution. Finally， the theoretical calculation for resonant energy transfer (RET)-induced enhancement in probability of exciting electron-hole pairs was conducted and the result is well corresponding to the enhanced PB peak of transient differential absorption in plasmonic CIGS. In CdSe quantum dots CIGS solar cells was observed by an external quantum efficiency， we confirmed the success of the photon down conversion mechanism to enhance optical conversion efficiency. These result has suggested that Surface Plasma Resonance and photon down-conversion mechanism are viable approachs to boosting high-efficiency CIGS solar cells.