Application of Single-Wall Carbon Nanotubes as Transparent Electrodes in Cu(In,Ga)Se2-Based Solar Cells

Abstract

We present a new thin-film solar cell structure in which the traditional transparent conductive oxide electrode (ZnO) is replaced by a transparent conductive coating consisting of a network of bundled single-wall carbon nanotubes. Optical transmission properties of these coatings are presented in relation to their electrical properties (sheet resistance), along with preliminary solar cell results from devices made using CuIn1-xGaxSe2 thinfilm absorber materials. Achieving an energy conversion efficiency of >12% and a quantum efficiency of~80% demonstrate the feasibility of the concept. A discussion of the device structures will be presented considering the physical properties of the new electrodes comparing current-voltage results from the new solar cell structure and those from standard ZnO/CdS/Cu(In,Ga)Se2/Mo solar cells.

Anode material based on SWCNT for infrared quantum dot light-emitting devices

“…The outcoupling efficiency of the device based on SWCNT anode improved more than 3.99 times relative to the device based on ITO anode. We attributed the improvement in the outcoupling efficiency to the superior IR transmission of CNT compared to ITO (Contreras et al 2006), also the high refractive index of SWCNT (n ∼ 1.99 at 1,550 nm) which lower the mismatch with high refractive index PbSe QD (n ∼ 4.6) (Wehrenberg et al 2002). Figure 3 shows a comparison between the effects of varying the wavelength on the optical characteristics of IR QD-LED based on ITO anode (Fig.…”

“…ITO is relatively brittle, which degrades its performance on flexible substrates (Green and Hersam 2008). Strong free-carrier absorption of infrared (IR) photons, which limits the device photo generated current in thin film photovoltaic (PV) devices (Contreras et al 2006). Also, ITO shows high reflectivity in the IR region (Kim et al 1999) and only transmits 70% at 1,500 nm (Steckel 2003).…”

“…The SWCNT-based electrodes are highly conductive in thin layers, and optical measurements indicate superior optical transmission (>80%) in the IR (wavelengths > 1,200 nm) compared to traditional ITO, in addition to the absence of free-carrier absorption in that region (Contreras et al 2006). These characteristics of SWCNT layer are a significant qualitative difference as compared to ITO.…”

“…These characteristics of SWCNT layer are a significant qualitative difference as compared to ITO. The SWCNT-based transparent electrodes have already been used in photovoltaic and OLEDs (Li et al 2006;Zhang et al 2006;Contreras et al 2006;Weeks et al 2006). However, to the best of our knowledge, they have not been employed in IR QD-LEDs.…”

Carbon Nanotube Transparent Electrodes

“…Photovoltaic [6], organic light emitting diode (LED) [12], and inorganic LED [10] devices have successfully used SWCNT networks as hole-selective contacts. Additionally, SWCNT networks often form rectifying contacts in applications where n þ -doped semiconductors are normally employed [78].…”