Thickness dependent photocurrent spectra and current-voltage characteristics of P3HT:PCBM photovoltaic devices

AbstractWe report the fabrication of photovoltaic devices by the anodization of microcrystalline silicon films on single crystal silicon substrates. The porosity of the films was varied from 20% to 60% by changing the anodization conditions. An unetched μc-Si based device was used for reference. The influence of the porosity on the series resistance (Rs), the reflectance, and the spectral response of the devices was studied in detail. In order to determine Rs, the current-voltage characteristics were analyzed, both in the dark and under illumination. We observed that the value of Rs increased from 3.1 Ω to 97 Ω and the value of the reflectance decreased from 24% to 7% when the porosity increased from 20% to 60%. Initially, an optimum device performance (fill factor of 0.53 and efficiency of 7.2%) was achieved for a porosity of 40%, which was about a 40% improvement as compared to the reference (unetched) μc-si based device. Due to a further reduction in Rs by using an intermediate ITO layer and a superior grid-contact architecture, a device efficiency of 10% has been recently achieved.

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Thickness Effect on F8T2/C60Bilayer Photovoltaic Devices

Journal of Nanotechnology ◽

10.1155/2012/513457 ◽

2012 ◽

Vol 2012 ◽

pp. 1-5

Author(s):

Natasha A. D. Yamamoto ◽

Andreia G. Macedo ◽

Lucimara S. Roman

Keyword(s):

Thermal Treatment ◽

Power Conversion Efficiency ◽

Variable Thickness ◽

Series Resistance ◽

Power Conversion ◽

Thickness Effect ◽

Photovoltaic Devices ◽

Current Voltage ◽

Current Voltage Characteristics ◽

Bilayer Devices

Copolymers based on fluorene-thiophene units have presented promising efficiencies in photovoltaic devices applications. They present good transport properties mainly after thermal treatment of the polymer films. Here, we investigate the properties of bilayer devices formed by the heterojunction of the polymer F8T2 with variable thickness and the fullerene. The series resistance of the equivalent circuit associated with the device increases as the polymer film gets thicker. The current-voltage characteristics of the bilayer devices follow the Mott-Gurney law of SCLC. For the best performing device we measured 2.1% of power conversion efficiency.

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Correlation among the ionization potential, built-in potential, and the open-circuit voltage of multi-layered organic photovoltaic devices

MRS Proceedings ◽

10.1557/opl.2011.233 ◽

2011 ◽

Vol 1286 ◽

Author(s):

Eiji Itoh ◽

Toshiki Shirotori

Keyword(s):

Ionization Potential ◽

Open Circuit Voltage ◽

Energy Difference ◽

Open Circuit ◽

Photovoltaic Devices ◽

Organic Photovoltaic Devices ◽

Extraction Buffer ◽

Current Voltage ◽

Current Voltage Characteristics ◽

P Type

ABSTRACTWe have investigated the current-voltage characteristics of the multi-layered photovoltaic devices consisting of ITO/oxide /p-type (donor)/fullerene/ bathocuproine (BCP)/ Al structures. We chose various p-type (donors) small molecules and polymers in order to tune the values of ionization potential (IP) of donor molecules. The open-circuit voltage (Voc) increases with the increment of IP of donor materials. However, VOC was limited at ~0.6-0.7V for the devices without oxide layer. On the other hand, the VOC increases up to 0.9V for the devices with NiO and to ~ 1.1V for the devices with MoOX as a hole extraction buffer layer, respectively. We also estimated the work-function differences between Al and the oxide as 0.7, 0.9-1.0, and 1.2-1.3 eV for the device without oxide, with NiO, and with MoOX, respectively. We therefore concluded the value of VOC is limited by the lower part of VOC and energy difference between the LUMO of fullerene and the HOMO of donor ΔE.

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