Category Organic Solar Cells
There are two important interfaces in HSCs, i. e., the polymer/inorganic nanocrystal interface where the charge separation takes place and the active layer/electrode interface where the free charges are collected. Therefore, their properties are crucial to the device performance. Efficient interface modification could not only facilitate the charge transport but also retard the backward recombination and remarkably improve the conversion efficiencies of the solar cells [61, 62, 65, 104–119].
One of the most important work on interface modification was reported by Goh et al. in 2007 , who systematically studied the effect of interface modification in TiO2/P3HT-based HSCs using different types of modifiers as shown in Fig. 9...Read More
Compared to the bilayer devices, bulk heterojunction HSCs have much higher conversion efficiencies. However, they are still limited by the inefficient charge transport caused by the discontinuous percolation pathways as shown in Fig. 9.10a, b. Therefore, an ordered heterojunction which has direct charge transport pathways is generally regarded as an ideal structure for HSCs, as shown in Fig. 9.10c .
The ordered heterojunction can be formed by infiltrating conjugated polymers into the vertically aligned nanostructures of the inorganic nanocrystals, such as nanorod, nanowire, and nanotube arrays that can be prepared by a variety of physical or chemical methods including nanoimprint [41, 78], low temperature liquid phase deposition , template method , anodization , etching [82...Read More
An important achievement in the development of CdSe-based HSCs was reported by Huynh et al. in 2002 . CdSe nanorods with aspect ratios ranging from 1 to 10 had been studied and the one with highest aspect ratio showed the most excellent charge transport property and gave the best performance with a milestone efficiency of 1.7 % under AM 1.5 global condition. After that, many efforts have been done toward the improvement of CdSe nanorods-based HSCs, Sun et al.  have studied the influences of solvents on the morphology and photovoltaic property of CdSe/P3HT blend film and a promising PCE of 2...Read More
The charge separation and transport in the conjugated polymer/semiconductor nanocrystals composites were first studied by Greenham et al. in 1996 . A HSC with ITO/MEH:PPV-CdSe/Al structure was fabricated, after incorporating 90 wt% of CdSe into the polymer matrix the device gave a 0.6 % PCE and a 12 % quantum efficiency at 514 nm, while the PCE could only approached 0.1 % under 80 mW/cm2 white light. After the breakthrough in control the shape of CdSe nanocrystals, CdSe quantum dots (QDs), nanorods, and tetrapods have been extensively studied [49–51]. Compared to the earlier CdSe QDs based HSCs, the PCEs have been improved by an order of magnitude, through the modification of CdSe QDs and the use of new polymers [52-54], however, the elongated CdSe nanocrystals were found to have better...Read More
HSCs have been extensively studied for many years. Although the conjugated polymers could play a crucial role in determining the efficiencies of HSCs, much of the research interests have been paid to the development of the inorganic nanocrystals. Although some new polymers with robust light harvesting properties and photovoltaic performances have been developed for organic solar cells [43-46], few have yet been used into HSCs . By now, most of the HSCs are based on polythiophene and poly(p-phenylene vinylene) and their derivatives are shown in Fig. 9.4. Herein, we will not discuss much about the conjugated polymers but focus on the proceedings in inorganic nanocrystals from the point of view of their
micromorphologies, i. e...Read More
The HSCs work in the same way as OSCs, where the conjugated polymers serve as light absorber and electron donor (D), the inorganic nanocrystals serve as electron acceptor (A). Figure 9.1 gives the schematic illustration of the energy level alignment and the photocurrent generation mechanism in HSCs. Upon illumination, the photocurrent is generated via the following processes [36, 38]:
(1) Photo absorption and exciton generation. The conjugated polymers mainly account for the light absorption in HSCs. In some cases, the inorganic nanocrystals could also absorb light, but the majority of the light absorption are attributed to the conjugated polymers. The light harvesting efficiency (gLHE) is determined by the bandgap (Eg) and the absorption coefficient of the polymers...Read More
Abstract In this chapter, we aim to present an overview of the development of the polymer/inorganic hybrid solar cells. In the first section, we introduce the basic concepts of hybrid solar cells including the device architecture and operation mechanism. Then we summarize the recent progress in this area classified by the nanomorphology of inorganic nanocrystals, including nanoparticles, nanorods, nanowires, and vertically aligned nanoarrays. The nanoscale morphology of the inorganic crystal could play a decisive role in determining the conversion efficiencies of the hybrid solar cells. Finally, we focus on the interface modifications involved in hybrid solar cells...Read More
In conclusion, by incorporating Au NPs into all organic layers in the OSCs, the efficiency can be improved by 22 %. The improvement is attributed to the accumulated enhancements in device performance due to addition of NPs into individual layers. NPs doped into PEDOT:PSS mainly contributes to more efficient hole collection due to increased PEDOT:PSS/P3HT:PCBM interfacial area, while NPs doped into the active layer improves optical absorption by LSPR effects and improves the hole mobility of the active layer. No optical coupling was observed between NPs in PEDOT:PSS and P3HT:PCBM. As the effects of NPs in PE – DOT:PSS or P3HT:PCBM are separated, the PCE improvement was attributed to the accumulated benefits of NPs in the individual organic layers...Read More