Due to its remarkable electrical and optical capabilities, optoelectronic devices based on the semiconducting single-walled carbon nanotube (s-SWCNT) have been studied extensively in the last two decades. First, s-SWCNT is a direct bandgap semiconductor with a high infrared absorption coefficient and high electron/hole mobility. In addition, as a typical one-dimensional material, there is no lattice mismatch between s-SWCNT and any substrates. Another advantage is that the optoelectronic devices of s-SWCNT can be processed at low temperatures. s-SWCNT has intriguing potential and applications in solar cells, light-emitting diodes (LEDs), photodetectors, and three-dimensional (3D) optoelectronic integration. In recent years, along with the advancement of solution purification technology, the high-purity s-SWCNTs film has laid the foundation for constructing large-area, homogenous, and high-performance optoelectronic devices. In this review, optoelectronic devices based on s-SWCNTs film and related topics are reviewed, including the preparation of high purity s-SWCNTs film, the progress of photodetectors based on the s-SWCNTs film, and challenges of s-SWCNTs film photodetectors.

Sub-micron color sensors are developed, using carbon nanotubes (CNTs). The color sensor consists of an array of two photodiodes with different spectral responses, fabricated using controlled electric peeling-off and doping-free techniques on a single semiconducting double-wall CNT. The CNT photodiodes exhibit intrinsic broad spectral responses from 640 to 2, 100 nm, large linear dynamic ranges of over 60 dB, and sub-micron pixel size. This method explores the unique properties of multi-wall CNTs, and may be readily used for large-scale fabrication of high performance color sensor arrays, when arrays of parallel multi-wall CNTs become available.

Random networks of single-walled carbon nanotubes (SWCNTs) were have been grown by chemical vapor deposition on silicon wafers and used for fabricating field-effect transistors (FETs) using symmetric Pd contacts and diodes using asymmetrical Pd and Sc contacts. For a short channel FET or diode with a channel length of about 1 μm or less, the device works in the direct transport regime, while for a longer channel device the transport mechanism changes to percolation. Detailed electronic and photovoltaic (PV) characterizations of these carbon nanotube (CNT) thin-film devices was carried out. While as-fabricated FETs exhibited typical p-type transfer characteristics, with a large current ON/OFF ratio of more than 10⁴ when metallic CNTs were removed via a controlled breakdown, it was found that the threshold voltage for the devices was typically very large, of the order of about 10 V. This situation was greatly improved when the device was coated with a passivation layer of 12 nm HfO₂, which effectively moved the threshold voltages of both FET and diode back to center around zero or turned these device to their OFF states when no bias was applied on the gate. PV measurements were then made on the short channel diodes under infrared laser illumination. It was shown that under an illumination power density of 1.5 kW/cm², the device resulted in an open circuit voltage V_OC = 0.21 V and a short circuit current I_SC = 3.74 nA. Furthermore, we compared PV characteristics of CNT film diodes with different channel lengths, and found that the power transform efficiency decreased significantly when the device changed from the direct transport to the percolation regime.