Transparent heat mirrors for solar-energy applications

Area of Science:

• Materials Science
• Optics
• Renewable Energy

Background:

• Transparent heat-mirror films are crucial for efficient solar energy utilization.
• These films selectively transmit solar radiation and reflect infrared thermal radiation.
• Applications include solar-thermal-electric conversion, solar heating, photovoltaics, and window insulation.

Purpose of the Study:

• To prepare and characterize transparent heat-mirror films using radio frequency (rf) sputtering.
• To evaluate the performance of TiO(2)/Ag/TiO(2) and Sn-doped In(2)O(3) films for solar energy collection.
• To define and assess effective solar absorptivity (alpha(eff)) and effective infrared emissivity (epsilon(eff)).

Main Methods:

• Radio frequency (rf) sputtering was employed to deposit two types of thin films: TiO(2)/Ag/TiO(2) and Sn-doped In(2)O(3).
• The optical properties of the prepared films were characterized to determine their performance as heat mirrors.
• Key parameters, effective solar absorptivity (alpha(eff)) and effective infrared emissivity (epsilon(eff)), were defined and measured.

Main Results:

• Sn-doped In(2)O(3) films exhibited an alpha(eff)/epsilon(eff) ratio comparable to leading selective absorbers.
• TiO(2)/Ag/TiO(2) films demonstrated even higher alpha(eff)/epsilon(eff) values, indicating superior performance.
• The developed films show significant potential for enhancing solar energy collection efficiency.

Conclusions:

• Both Sn-doped In(2)O(3) and TiO(2)/Ag/TiO(2) films are promising candidates for transparent heat-mirror applications.
• The TiO(2)/Ag/TiO(2) films present a particularly high performance ratio for solar energy applications.
• These findings contribute to the advancement of materials for efficient solar energy harvesting and thermal management.