![]() ![]() We sorted the SWNTs using a solution-based technique in which an organic polymer selectively dispersed the semiconducting SWNTs, a method previously developed by our group. The active layer was composed of a bilayer structure with polymer-sorted semiconducting SWNTs as the donor layer, and fullerenes (C 60) as the acceptor layer, which separates hole-electron pairs (excitons) produced when light is absorbed by the SWNTs. 5 We tested our device using both standard electrodes (ITO for the anode and silver for the cathode) or carbon-based electrodes (reduced graphene oxide for the anode and donor-doped SWNTs for the cathode). To address these issues, we fabricated the first all-carbon solar cell device (see Figure 1). P3DDT and PEDOT are conductive polymers, while PDMS is a flexible silicone polymer. Devices with both standard electrodes and carbon-based electrodes were fabricated. Structure of the carbon-based solar cell, showing the components of each layer and the process of electron-hole pair (exciton) generation and separation when light is absorbed. These materials are expensive, not solution processable, and not flexible-thus, they are not ideal choices.įigure 1. However, these devices use standard electrodes, such as indium tin oxide (ITO) as the bottom electrode (anode) and silver or aluminum as the top electrode (cathode). 2–4 These reports demonstrated the potential of carbon-based materials as the active elements in a solar cell. These solar cells consisted of an all-carbon photoactive layer using semiconducting single-walled carbon nanotubes (SWNTs) as the light-absorbing component and charge-donating (donor) material, with a fullerene layer as the charge-accepting (acceptor) material. Recently, scientists have reported solar-cell devices with power conversion efficiencies (PCEs) of 0.1–1.3%. Carbon devices can also have high chemical, thermal, and physical endurance as compared to those made with other materials. Additionally, these materials exhibit exceptional electrical and optical properties, so they are highly tunable and can be used in many types of devices such as transistors, solar cells, displays, and supercapacitors. 1 Due to its abundance and ease of processing in solution, carbon-based devices can potentially be made cheaply and in large quantities. Using a combination of these materials, it is possible to fabricate devices composed entirely of carbon-based components. Carbon allotropes include fullerenes (cage-like molecules of carbon), carbon nanotubes (high aspect-ratio cylindrical nanoparticles of carbon), and graphene (two-dimensional sheet of carbon). ![]() Carbon atoms can be arranged in many ways to produce a wide variety of compounds that have unique and interesting physical, chemical, and electronic properties. Carbon is one of the most abundant elements in the earth's crust and is found in several structural forms (allotropes). ![]()
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