Organic solar cell adopting weak epitaxial growth film as donor

Abstract

The invention relates to an organic solar cell adopting weak epitaxial growth films as donors. Large-size continuous p-type organic semiconductor polycrystalline films used as an induction layer is formed and grown on the surface of a smooth conducting substrate. The difference in work functions between the valence-band level of the induction layer and of the conducting substrate is less than 0.3 eV, thereby helping to the effective transmission of hole charge. By utilizing the interaction among different molecules, a high-quality p-type organic semiconductor layer is grown in a weak epitaxial way on the surface of the induction layer, and the organic solar cell is prepared on the basis of the semiconductor layer. The invention has the advantages of overcoming the disadvantage that the roughness increase of high-temperature deposition film and the formation of pinholes cause short circuit for devices in the prior method, greatly improving the performance of the devices and reaching the energy conversion efficiency of more than 3 percent. An OVPD method utilizes carrier gas to transport nano-crystalline molecules and directly deposits and forms nano-crystals on low-temperature electrodes. The method of the invention adopts a vacuum deposition method and needs no carrier gas.

Description

technical field [0001] The invention relates to an organic solar battery using a weak epitaxial growth film as a donor. Background technique [0002] In recent years, with the development of organic semiconductor science and technology, electronic devices based on organic semiconductors, such as organic light-emitting diodes, organic solar cells, and organic thin-film transistors, have potential applications. Organic materials are easy to process and come from a wide variety of raw materials, so organic devices are expected to be inexpensive. In 1986, American Applied Physics Letters (C.W.Tang, Applied Physics Letters 48, 183 (1986)) reported a photovoltaic cell using a double-layer organic heterojunction thin film structure, with an energy conversion efficiency of 0.95%. Since the photogenerated excitons can only be separated at the interface of the two organic semiconductors, the further improvement of the performance of this double-layer structure device is limited. In ...

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Problems solved by technology

However, due to the need for carrier gas transportation and precise control of the carrier gas flow rate, the cost is high and the experimental repeatability is poor.

In addition, due to the low substrate temperature (generally below 50°C), the grain size of the thin film is small and the mobility is low, which limits the further improvement of device performance.

[0005] On the other hand, researchers tried to increase the substrate temperature during deposition of organic small molecule films or use annealing method to prepare films with better crystallinity, but the roughness of films was increased due to high crystallinity (W.Geens, T.Aernouts, &G .J.Hadziioannou, Thin Solid Film, 403-404, 438(2002)), resulting in pinholes in the film and short circuits in the device (P.Peumans, S.Uchida, S.R.Forrest, Nature 425, 158(2003)) , in addition, the annealing process increases the complexity and cost of device fabrication, so it cannot be widely used in practical applications

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