Improvement in power conversion efficiency of organic photovoltaic devices by using excimer ultraviolet-radiation induced mesoporous silica anti-reflection coating

An anti-reflection thin film with a mesoporous structure is demonstrated to improve the light-collection and photocurrent-generation abilities of organic photovoltaic cells. The mesoporous film was prepared by sol-gel-derived silica with an excimer ultraviolet-radiation removable self-assembling triblock copolymer as the nanostructured template. The method for fabricating this film was much easier than conventional processes used to prepare anti-reflection materials as they involve vacuum or high-temperature conditions. By using this mesoporous film as an anti-reflection coating on the glass side of an indium tin oxide-coated glass substrate, an enhancement of about 6% in the photocurrent generation could be achieved in a device with a poly(3-hexylthiophene):(6,6)-phenyl-C61-butyric acid methyl ester bulk-heterojunction layer. A glass substrate with a coating of the mesoporous anti-reflection film showed an obvious improvement in transmittance for wavelengths extending from the visible-light region to the near-infrared region. The result also indicates that the prepared anti-reflection material is not only compatible with the photoactive materials with wide band gaps but works very well with semiconductors with small band gaps as well, e.g. thieno(3,4-b)-thiophene/benzodithiophene copolymer (PTB7). In this work, ~ 3.6% photocurrent enhancement can also be obtained in PTB7-based solar cells, indicating the wide compatibility of thus-prepared mesoporous film.