NDLI: Role of single walled carbon nanotubes in improving the efficiency of P3HT:PCBM solar cells - impedance spectroscopy and morphology studies

Content Provider	IEEE Xplore Digital Library
Author	Mallajosyula, A.T. Iyer, S.S.K. Mazhari, B.
Copyright Year	2010
Description	Author affiliation: Department of Electrical Engineering and Samtel Centre for Display Technologies, Indian Institute of Technology Kanpur, Uttar Pradesh, India (Mallajosyula, A.T.; Iyer, S.S.K.; Mazhari, B.)
Abstract	Bulk heterojunction (BHJ) solar cells of P3HT:PCBM doped with SWNTs were fabricated which doubled the efficiency over the undoped devices. No surface modifications of SWNTs were done during fabrication. Absorption and photoluminescence spectra along with photocurrent and spectral response of the devices show that SWNTs do not result in any significant charge generation at the P3HT:SWNT interface indicating that possible type-II heterojunctions between s-SWNTs and P3HT were dominated by the effects due to metallic tubes. At an optimum concentration of 0.75 wt% SWNTs, a 10% improvement in effective mobility was observed. In the voltage range of solar cell operation, two orders increase in injected current density is observed which has an Ohmic behavior. From the peak voltage of the capacitance-voltage characteristics, it was inferred that SWNTs reduce the V of the devices by only 60 mV. From the Cole-Cole in the diffusion transport regime, it was observed that the injected carrier life time gets lowered from 0.628 ms to 0.125 ms with SWNTs. A negative capacitance was observed in reverse bias in devices with SWNTs at low frequencies which has similar dependence on applied field as that in forward bias. This is attributed to the large reverse current injected through SWNT energy levels, making the effects of space charge, trapping, and recombination significant. The surface roughness and volume were more than doubled with SWNTs which resulted in increased cathode coverage area affecting the charge collection efficiency. Charge extraction efficiency is analyzed using the photocurrent loss normalized to the dark current where two orders of magnitude improvement is observed with SWNTs.
Starting Page	000095
Ending Page	000101
File Size	1406393
Page Count	7
File Format	PDF
ISBN	9781424458905
ISSN	01608371
e-ISBN	9781424458929
DOI	10.1109/PVSC.2010.5614483
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2010-06-20
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Films Photovoltaic cells Surface roughness Rough surfaces Cathodes Capacitance-voltage characteristics Photoconductivity
Content Type	Text
Resource Type	Article
Subject	Industrial and Manufacturing Engineering Control and Systems Engineering Electrical and Electronic Engineering

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