title: Carrier lifetime extension via the incorporation of robust hole/electron blocking layers in bulk heterojunction polymer solar cells.
abstract: We report the achievement of a power conversion efficiency (PCE) improvement in P3HT:PCBM-based bulk-heterojunction type polymer solar cells using photocrosslinked P3HT (c-P3HT) as the electron blocking/hole extraction layer and titanium oxide nanoparticles (TiO2) as the hole blocking/electron extraction layer. Devices prepared with a 20 nm thick c-P3HT layer showed an improved PCE of 3.4% compared to devices prepared without the c-P3HT layer (PCE = 3.0%). This improvement was attributed to an extension in the carrier lifetime and an enhancement in the carrier mobility. The incorporation of the c-P3HT layer lengthened (by more than a factor of 2) the carrier lifetime and increased (by a factor of 5) the hole mobility. These results suggest that the c-P3HT layer not only prevented non-geminate recombination but it also improved carrier transport. The PCE was further improved to 4.0% through the insertion of a TiO2 layer that acted as an effective hole-blocking layer at the interface between the photoactive layer and the cathode. This work demonstrates that the incorporation of solution-processable hole and electron blocking/extraction layers offers an effective means for preventing nongeminate recombination at the interfaces between a photoactive layer and an electrode in bulk-heterojunction-type polymer solar cells.
authors.affiliation: Photo-electronic Hybrids Research Center, Korea Institute of Science and Technology , Seoul 136-791, Republic of Korea.
authors.forename: Youngwoon
authors.initials: Y
authors.lastname: Yoon
authors.forename: Hyeong Jun
authors.initials: HJ
authors.lastname: Kim
authors.forename: Chul-Hee
authors.initials: CH
authors.lastname: Cho
authors.forename: Seulki
authors.initials: S
authors.lastname: Kim
authors.forename: Hae Jung
authors.initials: HJ
authors.lastname: Son
authors.forename: Min-Jae
authors.initials: MJ
authors.lastname: Ko
authors.forename: Honggon
authors.initials: H
authors.lastname: Kim
authors.forename: Doh-Kwon
authors.initials: DK
authors.lastname: Lee
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Wonmok
authors.initials: W
authors.lastname: Lee
authors.forename: Bumjoon J
authors.initials: BJ
authors.lastname: Kim
authors.forename: BongSoo
authors.initials: B
authors.lastname: Kim