Photovoltaic response of polymer solar cells to the surface-treated NiOx hole transport layers

• Main Authors: Hwa-Wei Shih, 施華偉
• Other Authors: Forest Shih-Sen Chien
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/54173326583422728635

碩士 === 東海大學 === 物理學系 === 101 === Polymer solar cells (PSCs) have attracted great interest in the field of green energy resources. However, the efficiencies of PSCs were relative lower than solid solar cells. In this study, the p-type semiconductor, NiOx thin films were unitized as hole transport layers (HTLs) for PSCs. The NiOx HTLs were optimized in terms of the thickness and O2 flow rate during growth. It was observed that the PSC with 15-nm thick HTL, which was prepared by sputtering with 10% flow rate ratio of O2/(Ar+O2), performed the best photovoltaic performance with a 2.4% of power conversion efficiency (PCE), 8.6 mA/cm2 of short-cirucit current density (Jsc), and a 579 mV of open-circuit voltage. It has been reported that the surface treatments on solid state HTLs/or electron transport layers lead to significant improvement in PCE of PSC. In this study, the surface treatments on NiOx were employed to improve the PCEs of PSCs, including: (1) O2 plasma treatment; (2) H2O2 treatment; (3) Self-assembled monolayer; and (4) AuNPs modification by self-assembled method. From the results of photovoltaic characteristics of PSCs with O2 plasma treated HTLs, it showed that the Jsc increased from 8.5 mA/cm2 to 8.8 mA/cm2 and PCE from 2.4% to 2.6%. It is regard that the work function difference between P3HT and HTL was reduced by the plasma treatment. However, corrosion phenomena of NiOx were observed after the thin film was subject to the H2O2 treatment and MPTMS modification. The PSCs with H2O2 and MPTMS treated HTL presented poor photovoltaic performance because of the corrosion. On the other hand, it was obtained that the PSC with APTMS treated HTL dropped the photovoltaic performance due to bad filling factor. Therefore, the post O2 plasma treatment on APTMS-treated HTL was introduced, and the photovoltaic performance of PSC was improved. To prepare AuNPs onto HTL, the self-assemble monolayer of APTMS was performed. From the transmittance spectrum, there was a absorption peak at ~520 nm of wavelength, which indicated the localized surface plasmon resonance (LSPR) absorption of 50-nm AuNPs. Therefore, the aggregation of AuNPs leads short contact between HTL and Al electrode, and the performance of PSCs dropped badly. A post deposition of 3-nm NiOx was performed to solve the problem. However, no improvement in PCE and IPCE was observed in the photovoltaic characteristic measurements. It is suggested that: the density of AuNPs is too low to induce the LSPR to enhance the absorption of active layer.