Chemical Vapor Deposited Graphene-Based Derivative As High-Performance Hole Transport Material for Organic Photovoltaics

Abstract

PSS as hole transport/electron blocking layer in solution-processed organic photovoltaics.

The Role of Graphene‐Based Derivative as Interfacial Layer in Graphene/n‐Si Schottky Barrier Solar Cells

“…The spectrum of FLG reported in Figure a has I 2D /I G < 1 and I D /I G ≈ 0.13, confirming the formation of FLG with low defect density . The spectrum of GBD is also reported and confirms the structural characteristics of films grown in the same conditions . The D, G and 2D peaks are still present, but in this case the D peak strongly intensifies and the defect‐related D’ peak at ∼ 1620 cm −1 appears .…”

“…Graphene‐based films were grown by CVD of ethanol on Cu substrates by varying the process temperature: FLG at 1070 °C and GBD at 790 °C, as previously reported . The CVD apparatus consists of a cold‐wall chamber, made of a quartz tube equipped with an inductively coupled graphite susceptor heater.…”

“…In the present work, we report on the use of a GBD made by chemical vapor deposition (CVD) to be used in a SBSC as interfacial layer between few‐layer graphene (FLG, acting as transparent conductive electrode) and n‐Si (the absorber). Specifically, this GBD is grown by ethanol‐CVD at ≈800° C (i.e., a temperature 200° C lower than the standard one used to grow graphene) and as a result its lattice is less crystalline on the long range than pristine graphene and contains heterogeneous groups composed of a mixed phase of sp 2 /sp 3 ‐hybridized carbon atoms such as hydrogenated (CH), carboxyl (COH), or epoxide (COC) bonds . These features reflects in a higher sheet resistance than graphene's, as well as modified UV–vis absorbance and work function (Wf) .…”

“…Specifically, this GBD is grown by ethanol‐CVD at ≈800° C (i.e., a temperature 200° C lower than the standard one used to grow graphene) and as a result its lattice is less crystalline on the long range than pristine graphene and contains heterogeneous groups composed of a mixed phase of sp 2 /sp 3 ‐hybridized carbon atoms such as hydrogenated (CH), carboxyl (COH), or epoxide (COC) bonds . These features reflects in a higher sheet resistance than graphene's, as well as modified UV–vis absorbance and work function (Wf) . The structural and electronic properties of the GBD were measured by Raman spectroscopy, atomic force microscopy (AFM), scanning Kelvin probe, and UV–vis absorption spectroscopy.…”

“…FLG and GBD were integrated into the SBSC architecture by direct transfer of carbon films on Si substrate at room temperature, thus at a lower temperature than the conventional Al 2 O 3 or HfO 2 insulating layers deposited by Plasma enhanced chemical vapor deposition (PECVD) at 600 °C and Atomic Layer Deposition (ALD) at 200 °C . The GBD, acting as non‐conductive hole transport layer, reduces the recombination at the interface and improves the overall cell performance. The devices were tested in dark and light conditions, and the results were compared with a reference solar cell without interfacial layer.…”