Organic Solar Cells: Problems and Perspectives

Abstract

For photovoltaic cells to convert solar into electric energy is probably the most interesting research challenge nowadays. A good efficiency of these devices has been obtained by using inorganic semiconductor materials. On the other hand, manufacture processes are very expensive in terms of both materials and techniques. For this reason organic-based photovoltaic (OPV) cells are attracting the general attention because of the possible realization of more economical devices. Organic materials are abundant and easily handling. Unfortunately OPV cells efficiency is significantly lower than that of inorganic-based devices, representing a big point of weakness at the present. This is mainly due to the fact that organic semiconductors have a much higher band gap with respect to inorganic semiconductors. In addition, OPV cells are very susceptible to oxygen and water. In this paper we will describe some of the different approaches to the understanding and improving of organic photovoltaic devices.

Anisotropy of singlet exciton diffusion in organic semiconductor crystals from ab initio approaches

“…The mobility is with Eqs. (12) and (13) From this it follows that Figure 2 shows a typical FCWDJ 1 (E ji ) (solid line, Eq. (2) with the delta function replaced by (9)) depending on the energetic shift E ji = − F r ji .J 2 (E ji ) (dotted line) is calculated with the simpler Marcus theory 55-57 which incorporates only one effective vibrational mode.…”

“…Important fields for application are organic light emitting diodes (OLEDs), 1-3 organic field effect transistors (OFETs), 4-6 radio frequency identification tags (RFIDs), 7,8 and solar cells, [9][10][11][12][13] to mention just a few. Especially for solar cells the exciton diffusion length is a crucial parameter.…”

Valence and Conduction Band States of PCBM as Probed by Photoelectron Spectroscopy at Resonant Excitation

“…In particular, (6,6)-phenyl C 61 butyric acid methyl ester (PCBM) is a well-known and extensively applied candidate. In the field of organic bulk heterojunction solar cells, PCBM is commonly used as the electron acceptor [1]. In organic field effect transistors, Fullerenes function as electron-transporting semiconductor (n-channel) [2].…”

Enhanced lifetime of organic photovoltaic diodes utilizing a ternary blend including an insulating polymer

“…Although the lifetime of poly(3-hexylthiophene) (P3HT) : phenyl-C61-butyric acid methyl ester (PCBM) devices can be up to 1000 hours [6], this still represents significantly worse performance than, for example, inorganic silicon photovoltaics, which have a lifetime approaching 25 years [7]. The degradation mechanisms in OPVs are not fully understood [8] and a considerable effort is needed to improve their lifetime. OPVs degrade due to both chemical and physical processes.…”